Omega-3 fatty acid
|Types of fats in food|
Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or n−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond three atoms away from the terminal methyl group in their chemical structure. They are widely distributed in nature, being important constituents of animal lipid metabolism, and they play an important role in the human diet and in human physiology. The three types of omega−3 fatty acids involved in human physiology are α-linolenic acid (ALA), found in plant oils, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both commonly found in marine oils. Marine algae and phytoplankton are primary sources of omega−3 fatty acids. Common sources of plant oils containing ALA include walnut, edible seeds, clary sage seed oil, algal oil, flaxseed oil, Sacha Inchi oil, Echium oil, and hemp oil, while sources of animal omega−3 fatty acids EPA and DHA include fish, fish oils, eggs from chickens fed EPA and DHA, squid oils and krill oil.
Mammals are unable to synthesize the essential omega−3 fatty acid ALA and can only obtain it through diet. However, they can use ALA, when available, to form EPA and DHA, by creating additional double bonds along its carbon chain (desaturation) and extending it (elongation). Namely, ALA (18 carbons and 3 double bonds) is used to make EPA (20 carbons and 5 double bonds), which is then used to make DHA (22 carbons and 6 double bonds). The ability to make the longer-chain omega−3 fatty acids from ALA may be impaired in aging. In foods exposed to air, unsaturated fatty acids are vulnerable to oxidation and rancidity. Dietary supplementation with omega−3 fatty acids does not appear to affect the risk of death, cancer or heart disease. Furthermore, fish oil supplement studies have failed to support claims of preventing heart attacks or strokes or any vascular disease outcomes.
The terms ω–3 ("omega–3") fatty acid and n–3 fatty acid are derived from organic nomenclature. One way in which an unsaturated fatty acid is named is determined by the location, in its carbon chain, of the double bond which is closest to the methyl end of the molecule. In general terminology, n (or ω) represents the locant of the methyl end of the molecule, while the number n–x (or ω–x) refers to the locant of its nearest double bond. Thus, in omega–3 fatty acids in particular, there is a double bond located at the carbon numbered 3, starting from the methyl end of the fatty acid chain. This classification scheme is useful since most chemical changes occur at the carboxyl end of the molecule, while the methyl group and its nearest double bond are unchanged in most chemical or enzymatic reactions.
In the expressions n–x or ω–x, the dash is actually meant to be a minus sign, although it is never read as such. Also, the symbol n (or ω) represents the locant of the methyl end, counted from the carboxyl end of the fatty acid carbon chain. For instance, in an omega-3 fatty acid with 18 carbon atoms (see illustration), where the methyl end is at location 18 from the carboxyl end, n (or ω) represents the number 18, and the notation n–3 (or ω–3) represents the subtraction 18–3 = 15, where 15 is the locant of the double bond which is closest to the methyl end, counted from the carboxyl end of the chain.
Although n and ω (omega) are synonymous, the IUPAC recommends that n be used to identify the highest carbon number of a fatty acid. Nevertheless, the more common name – omega–3 fatty acid – is used in both the lay media and scientific literature.
By example, α-linolenic acid (ALA; illustration) is an 18-carbon chain having three double bonds, the first being located at the third carbon from the methyl end of the fatty acid chain. Hence, it is an omega–3 fatty acid. Counting from the other end of the chain, that is the carboxyl end, the three double bonds are located at carbons 9, 12, and 15. These three locants are typically indicated as Δ9c,12c,15c, or cisΔ9,cisΔ12,cisΔ15, or cis-cis-cis-Δ9,12,15, where c or cis means that the double bonds have a cis configuration.
The evidence linking the consumption of marine omega−3 fats to a lower risk of cancer is poor. With the possible exception of breast cancer, there is insufficient evidence that supplementation with omega−3 fatty acids has an effect on different cancers. The effect of consumption on prostate cancer is not conclusive. There is a decreased risk with higher blood levels of DPA, but an increased risk of more aggressive prostate cancer was shown with higher blood levels of combined EPA and DHA. In people with advanced cancer and cachexia, omega−3 fatty acids supplements may be of benefit, improving appetite, weight, and quality of life.
Evidence in the population generally does not support a beneficial role for omega−3 fatty acid supplementation in preventing cardiovascular disease (including myocardial infarction and sudden cardiac death) or stroke.[needs update] A 2018 meta-analysis found no support that daily intake of one gram of omega-3 fatty acid in individuals with a history of coronary heart disease prevents fatal coronary heart disease, nonfatal myocardial infarction or any other vascular event. However, omega−3 fatty acid supplementation greater than one gram daily for at least a year may be protective against cardiac death, sudden death, and myocardial infarction in people who have a history of cardiovascular disease. No protective effect against the development of stroke or all-cause mortality was seen in this population. A 2018 study found that omega-3 supplementation was helpful in protecting cardiac health in those who did not regularly eat fish, particularly in the African American population. Eating a diet high in fish that contain long chain omega−3 fatty acids does appear to decrease the risk of stroke. Fish oil supplementation has not been shown to benefit revascularization or abnormal heart rhythms and has no effect on heart failure hospital admission rates. Furthermore, fish oil supplement studies have failed to support claims of preventing heart attacks or strokes. In the EU, a review by the European Medicines Agency of omega-3 fatty acid medicines containing a combination of an ethyl ester of eicosapentaenoic acid and docosahexaenoic acid at a dose of 1 g per day concluded that these medicines are not effective in secondary prevention of heart problems in patients who have had a myocardial infarction.
Evidence suggests that omega−3 fatty acids modestly lower blood pressure (systolic and diastolic) in people with hypertension and in people with normal blood pressure. Some evidence suggests that people with certain circulatory problems, such as varicose veins, may benefit from the consumption of EPA and DHA, which may stimulate blood circulation and increase the breakdown of fibrin, a protein involved in blood clotting and scar formation. Omega−3 fatty acids reduce blood triglyceride levels but do not significantly change the level of LDL cholesterol or HDL cholesterol in the blood. The American Heart Association position (2011) is that borderline elevated triglycerides, defined as 150–199 mg/dL, can be lowered by 0.5-1.0 grams of EPA and DHA per day; high triglycerides 200–499 mg/dL benefit from 1-2 g/day; and >500 mg/dL be treated under a physician's supervision with 2-4 g/day using a prescription product. In this population omega-3 fatty acid supplementation decreases the risk of heart disease by about 25%.
ALA does not confer the cardiovascular health benefits of EPA and DHAs.
The effect of omega−3 polyunsaturated fatty acids on stroke is unclear, with a possible benefit in women.
A 2013 systematic review found tentative evidence of benefit for lowering inflammation levels in healthy adults and in people with one or more biomarkers of metabolic syndrome. Consumption of omega−3 fatty acids from marine sources lowers blood markers of inflammation such as C-reactive protein, interleukin 6, and TNF alpha.
For rheumatoid arthritis, one systematic review found consistent, but modest, evidence for the effect of marine n−3 PUFAs on symptoms such as "joint swelling and pain, duration of morning stiffness, global assessments of pain and disease activity" as well as the use of non-steroidal anti-inflammatory drugs. The American College of Rheumatology has stated that there may be modest benefit from the use of fish oils, but that it may take months for effects to be seen, and cautions for possible gastrointestinal side effects and the possibility of the supplements containing mercury or vitamin A at toxic levels. The National Center for Complementary and Integrative Health has concluded that "supplements containing omega-3 fatty acids ... may help relieve rheumatoid arthritis symptoms" and warns that such supplements "may interact with drugs that affect blood clotting".
Although not supported by current scientific evidence as a primary treatment for attention deficit hyperactivity disorder (ADHD), autism, and other developmental disabilities, omega−3 fatty acid supplements are being given to children with these conditions.
One meta-analysis concluded that omega−3 fatty acid supplementation demonstrated a modest effect for improving ADHD symptoms. A Cochrane review of PUFA (not necessarily omega−3) supplementation found "there is little evidence that PUFA supplementation provides any benefit for the symptoms of ADHD in children and adolescents", while a different review found "insufficient evidence to draw any conclusion about the use of PUFAs for children with specific learning disorders". Another review concluded that the evidence is inconclusive for the use of omega−3 fatty acids in behavior and non-neurodegenerative neuropsychiatric disorders such as ADHD and depression.
Fish oil has only a small benefit on the risk of premature birth. A 2015 meta-analysis of the effect of omega−3 supplementation during pregnancy did not demonstrate a decrease in the rate of preterm birth or improve outcomes in women with singleton pregnancies with no prior preterm births. A 2018 Cochrane systematic review with moderate to high quality of evidence suggested that omega−3 fatty acids may reduce risk of perinatal death, risk of low body weight babies; and possibly mildly increased LGA babies. However, a 2019 clinical trial in Australia showed no significant reduction on rate of preterm delivery, and no higher incidence of interventions in post-term deliveries than control.
There is evidence that omega−3 fatty acids are related to mental health, particularly for depression where there are now large meta-analyses showing treatment efficacy compared to placebo. These data have also recently resulted in international clinical guidelines regarding the use omega-3 fatty acids in the treatment of depression. The link between omega−3 and depression has been attributed to the fact that many of the products of the omega−3 synthesis pathway play key roles in regulating inflammation (such as prostaglandin E3) which have been linked to depression. This link to inflammation regulation has been supported in both in vivo studies and in a meta-analysis. omega-3 fatty acids have also been investigated as an add-on for the treatment of depression associated with bipolar disorder. Significant benefits due to EPA supplementation were only seen, however, when treating depressive symptoms and not manic symptoms suggesting a link between omega−3 and depressive mood.
In contrast to dietary supplementation studies, there is significant difficulty in interpreting the literature regarding dietary intake of omega-3 fatty acids (e.g. from fish) due to participant recall and systematic differences in diets. There is also controversy as to the efficacy of omega−3, with many meta-analysis papers finding heterogeneity among results which can be explained mostly by publication bias. A significant correlation between shorter treatment trials was associated with increased omega−3 efficacy for treating depressed symptoms further implicating bias in publication. One review found that "Although evidence of benefits for any specific intervention is not conclusive, these findings suggest that it might be possible to delay or prevent transition to psychosis."`
Epidemiological studies are inconclusive about an effect of omega−3 fatty acids on the mechanisms of Alzheimer's disease. There is preliminary evidence of effect on mild cognitive problems, but none supporting an effect in healthy people or those with dementia.
Brain and visual functions
Brain function and vision rely on dietary intake of DHA to support a broad range of cell membrane properties, particularly in grey matter, which is rich in membranes. A major structural component of the mammalian brain, DHA is the most abundant omega−3 fatty acid in the brain. It is under study as a candidate essential nutrient with roles in neurodevelopment, cognition, and neurodegenerative disorders.
Results of studies investigating the role of LCPUFA supplementation and LCPUFA status in the prevention and therapy of atopic diseases (allergic rhinoconjunctivitis, atopic dermatitis and allergic asthma) are controversial; therefore, at the present stage of our knowledge (as of 2013) we cannot state either that the nutritional intake of n−3 fatty acids has a clear preventive or therapeutic role, or that the intake of n-6 fatty acids has a promoting role in context of atopic diseases.
Risk of deficiency
An omega−3 fatty acid is a fatty acid with multiple double bonds, where the first double bond is between the third and fourth carbon atoms from the end of the carbon atom chain. "Short chain" omega−3 fatty acids have a chain of 18 carbon atoms or less, while "long chain" omega−3 fatty acids have a chain of 20 or more.
Three omega−3 fatty acids are important in human physiology, α-linolenic acid (18:3, n-3; ALA), eicosapentaenoic acid (20:5, n-3; EPA), and docosahexaenoic acid (22:6, n-3; DHA). These three polyunsaturates have either 3, 5, or 6 double bonds in a carbon chain of 18, 20, or 22 carbon atoms, respectively. As with most naturally-produced fatty acids, all double bonds are in the cis-configuration, in other words, the two hydrogen atoms are on the same side of the double bond; and the double bonds are interrupted by methylene bridges (-CH
2-), so that there are two single bonds between each pair of adjacent double bonds.
List of omega−3 fatty acids
This table lists several different names for the most common omega−3 fatty acids found in nature.
|Common name||Lipid number||Chemical name|
|Hexadecatrienoic acid (HTA)||16:3 (n-3)||all-cis-7,10,13-hexadecatrienoic acid|
|α-Linolenic acid (ALA)||18:3 (n-3)||all-cis-9,12,15-octadecatrienoic acid|
|Stearidonic acid (SDA)||18:4 (n-3)||all-cis-6,9,12,15-octadecatetraenoic acid|
|Eicosatrienoic acid (ETE)||20:3 (n-3)||all-cis-11,14,17-eicosatrienoic acid|
|Eicosatetraenoic acid (ETA)||20:4 (n-3)||all-cis-8,11,14,17-eicosatetraenoic acid|
|Eicosapentaenoic acid (EPA)||20:5 (n-3)||all-cis-5,8,11,14,17-eicosapentaenoic acid|
|Heneicosapentaenoic acid (HPA)||21:5 (n-3)||all-cis-6,9,12,15,18-heneicosapentaenoic acid|
|Docosapentaenoic acid (DPA),
|22:5 (n-3)||all-cis-7,10,13,16,19-docosapentaenoic acid|
|Docosahexaenoic acid (DHA)||22:6 (n-3)||all-cis-4,7,10,13,16,19-docosahexaenoic acid|
|Tetracosapentaenoic acid||24:5 (n-3)||all-cis-9,12,15,18,21-tetracosapentaenoic acid|
|Tetracosahexaenoic acid (Nisinic acid)||24:6 (n-3)||all-cis-6,9,12,15,18,21-tetracosahexaenoic acid|
Omega−3 fatty acids occur naturally in two forms, triglycerides and phospholipids. In the triglycerides, they, together with other fatty acids, are bonded to glycerol; three fatty acids are attached to glycerol. Phospholipid omega−3 is composed of two fatty acids attached to a phosphate group via glycerol.
The triglycerides can be converted to the free fatty acid or to methyl or ethyl esters, and the individual esters of omega−3 fatty acids are available.[clarification needed]
Mechanism of action
The 'essential' fatty acids were given their name when researchers found that they are essential to normal growth in young children and animals. The omega−3 fatty acid DHA, also known as docosahexaenoic acid, is found in high abundance in the human brain. It is produced by a desaturation process, but humans lack the desaturase enzyme, which acts to insert double bonds at the ω6 and ω3 position. Therefore, the ω6 and ω3 polyunsaturated fatty acids cannot be synthesized, are appropriately called essential fatty acids, and must be obtained from the diet.
In 1964, it was discovered that enzymes found in sheep tissues convert omega−6 arachidonic acid into the inflammatory agent, prostaglandin E2, which is involved in the immune response of traumatized and infected tissues. By 1979, eicosanoids were further identified, including thromboxanes, prostacyclins, and leukotrienes. The eicosanoids typically have a short period of activity in the body, starting with synthesis from fatty acids and ending with metabolism by enzymes. If the rate of synthesis exceeds the rate of metabolism, the excess eicosanoids may have deleterious effects. Researchers found that certain omega−3 fatty acids are also converted into eicosanoids and docosanoids, but at a slower rate. If both omega−3 and omega−6 fatty acids are present, they will "compete" to be transformed, so the ratio of long-chain omega−3:omega−6 fatty acids directly affects the type of eicosanoids that are produced.
Conversion efficiency of ALA to EPA and DHA
Humans can convert short-chain omega−3 fatty acids to long-chain forms (EPA, DHA) with an efficiency below 5%. The omega−3 conversion efficiency is greater in women than in men, but less studied. Higher ALA and DHA values found in plasma phospholipids of women may be due to the higher activity of desaturases, especially that of delta-6-desaturase.
These conversions occur competitively with omega−6 fatty acids, which are essential closely related chemical analogues that are derived from linoleic acid. They both utilize the same desaturase and elongase proteins in order to synthesize inflammatory regulatory proteins. The products of both pathways are vital for growth making a balanced diet of omega−3 and omega−6 important to an individual's health. A balanced intake ratio of 1:1 was believed to be ideal in order for proteins to be able to synthesize both pathways sufficiently, but this has been controversial as of recent research.
The conversion of ALA to EPA and further to DHA in humans has been reported to be limited, but varies with individuals. Women have higher ALA-to-DHA conversion efficiency than men, which is presumed to be due to the lower rate of use of dietary ALA for beta-oxidation. One preliminary study showed that EPA can be increased by lowering the amount of dietary linoleic acid, and DHA can be increased by elevating intake of dietary ALA.
Omega−6 to omega−3 ratio
Human diet has changed rapidly in recent centuries resulting in a reported increased diet of omega−6 in comparison to omega−3. The rapid evolution of human diet away from a 1:1 omega−3 and omega−6 ratio, such as during the Neolithic Agricultural Revolution, has presumably been too fast for humans to have adapted to biological profiles adept at balancing omega−3 and omega−6 ratios of 1:1. This is commonly believed to be the reason why modern diets are correlated with many inflammatory disorders. While omega−3 polyunsaturated fatty acids may be beneficial in preventing heart disease in humans, the level of omega−6 polyunsaturated fatty acids (and, therefore, the ratio) does not matter.
Both omega−6 and omega−3 fatty acids are essential: humans must consume them in their diet. Omega−6 and omega−3 eighteen-carbon polyunsaturated fatty acids compete for the same metabolic enzymes, thus the omega−6:omega−3 ratio of ingested fatty acids has significant influence on the ratio and rate of production of eicosanoids, a group of hormones intimately involved in the body's inflammatory and homeostatic processes, which include the prostaglandins, leukotrienes, and thromboxanes, among others. Altering this ratio can change the body's metabolic and inflammatory state. In general, grass-fed animals accumulate more omega−3 than do grain-fed animals, which accumulate relatively more omega−6. Metabolites of omega−6 are more inflammatory (esp. arachidonic acid) than those of omega−3. This necessitates that omega−6 and omega−3 be consumed in a balanced proportion; healthy ratios of omega−6:omega−3, according to some authors, range from 1:1 to 1:4. Other authors believe that a ratio of 4:1 (4 times as much omega−6 as omega−3) is already healthy. Studies suggest the evolutionary human diet, rich in game animals, seafood, and other sources of omega−3, may have provided such a ratio.
Typical Western diets provide ratios of between 10:1 and 30:1 (i.e., dramatically higher levels of omega−6 than omega−3). The ratios of omega−6 to omega−3 fatty acids in some common vegetable oils are: canola 2:1, hemp 2–3:1, soybean 7:1, olive 3–13:1, sunflower (no omega−3), flax 1:3, cottonseed (almost no omega−3), peanut (no omega−3), grapeseed oil (almost no omega−3) and corn oil 46:1.
On September 8, 2004, the U.S. Food and Drug Administration gave "qualified health claim" status to EPA and DHA omega−3 fatty acids, stating, "supportive but not conclusive research shows that consumption of EPA and DHA [omega−3] fatty acids may reduce the risk of coronary heart disease". This updated and modified their health risk advice letter of 2001 (see below).
The Canadian Food Inspection Agency has recognized the importance of DHA omega−3 and permits the following claim for DHA: "DHA, an omega−3 fatty acid, supports the normal physical development of the brain, eyes and nerves primarily in children under two years of age."
Historically, whole food diets contained sufficient amounts of omega−3, but because omega−3 is readily oxidized, the trend to shelf-stable, processed foods has led to a deficiency in omega−3 in manufactured foods.
|Common name||grams omega−3|
|Tuna (canned, light)||0.17–0.24|
|Hoki (blue grenadier)||0.41|
|Blue eye cod||0.31|
|Sydney rock oysters||0.30|
|Eggs, large regular||0.109|
|Strawberry or Kiwifruit||0.10–0.20|
|Giant tiger prawn||0.100|
|Lean red meat||0.031|
In the United States, the Institute of Medicine publishes a system of Dietary Reference Intakes, which includes Recommended Dietary Allowances (RDAs) for individual nutrients, and Acceptable Macronutrient Distribution Ranges (AMDRs) for certain groups of nutrients, such as fats. When there is insufficient evidence to determine an RDA, the institute may publish an Adequate Intake (AI) instead, which has a similar meaning, but is less certain. The AI for α-linolenic acid is 1.6 grams/day for men and 1.1 grams/day for women, while the AMDR is 0.6% to 1.2% of total energy. Because the physiological potency of EPA and DHA is much greater than that of ALA, it is not possible to estimate one AMDR for all omega−3 fatty acids. Approximately 10 percent of the AMDR can be consumed as EPA and/or DHA. The Institute of Medicine has not established a RDA or AI for EPA, DHA or the combination, so there is no Daily Value (DVs are derived from RDAs), no labeling of foods or supplements as providing a DV percentage of these fatty acids per serving, and no labeling a food or supplement as an excellent source, or "High in..." As for safety, there was insufficient evidence as of 2005 to set an upper tolerable limit for omega−3 fatty acids, although the FDA has advised that adults can safely consume up to a total of 3 grams per day of combined DHA and EPA, with no more than 2 g from dietary supplements.
The American Heart Association (AHA) has made recommendations for EPA and DHA due to their cardiovascular benefits: individuals with no history of coronary heart disease or myocardial infarction should consume oily fish two times per week; and "Treatment is reasonable" for those having been diagnosed with coronary heart disease. For the latter the AHA does not recommend a specific amount of EPA + DHA, although it notes that most trials were at or close to 1000 mg/day. The benefit appears to be on the order of a 9% decrease in relative risk. The European Food Safety Authority (EFSA) approved a claim "EPA and DHA contributes to the normal function of the heart" for products that contain at least 250 mg EPA + DHA. The report did not address the issue of people with pre-existing heart disease. The World Health Organization recommends regular fish consumption (1-2 servings per week, equivalent to 200 to 500 mg/day EPA + DHA) as protective against coronary heart disease and ischaemic stroke.
Heavy metal poisoning from consuming fish oil supplements is highly unlikely, because heavy metals (mercury, lead, nickel, arsenic, and cadmium) selectively bind with protein in the fish flesh rather than accumulate in the oil.
Throughout their history, the Council for Responsible Nutrition and the World Health Organization have published acceptability standards regarding contaminants in fish oil. The most stringent current standard is the International Fish Oils Standard.[non-primary source needed] Fish oils that are molecularly distilled under vacuum typically make this highest-grade; levels of contaminants are stated in parts per billion per trillion.
The most widely available dietary source of EPA and DHA is oily fish, such as salmon, herring, mackerel, anchovies, menhaden, and sardines. Oils from these fish have a profile of around seven times as much omega−3 as omega−6. Other oily fish, such as tuna, also contain n-3 in somewhat lesser amounts. Consumers of oily fish should be aware of the potential presence of heavy metals and fat-soluble pollutants like PCBs and dioxins, which are known to accumulate up the food chain. After extensive review, researchers from Harvard's School of Public Health in the Journal of the American Medical Association (2006)  reported that the benefits of fish intake generally far outweigh the potential risks. Although fish are a dietary source of omega−3 fatty acids, fish do not synthesize them; they obtain them from the algae (microalgae in particular) or plankton in their diets. In the case of farmed fish, omega-3 fatty acids are provided by fish oil; In 2009, 81% of the global fish oil production is used by aquaculture.
Not all forms of fish oil may be equally digestible. Of four studies that compare bioavailability of the glyceryl ester form of fish oil vs. the ethyl ester form, two have concluded the natural glyceryl ester form is better, and the other two studies did not find a significant difference. No studies have shown the ethyl ester form to be superior, although it is cheaper to manufacture.
Krill oil is a source of omega−3 fatty acids. The effect of krill oil, at a lower dose of EPA + DHA (62.8%), was demonstrated to be similar to that of fish oil on blood lipid levels and markers of inflammation in healthy humans. While not an endangered species, krill are a mainstay of the diets of many ocean-based species including whales, causing environmental and scientific concerns about their sustainability. Preliminary studies appear to indicate that the DHA and EPA omega-3 fatty acids found in krill oil may be more bio-available than in fish oil. Additionally, krill oil contains astaxanthin, a marine-source keto-carotenoid antioxidant that may act synergistically with EPA and DHA.
|Common name||Alternative name||Linnaean name||% ALA|
|Kiwifruit seed oil||Chinese gooseberry||Actinidia deliciosa||63|
|Chia seed||chia sage||Salvia hispanica||58|
|Flax||linseed||Linum usitatissimum||53 – 59|
|Fig seed oil||Common Fig||Ficus carica||47.7|
|Black raspberry||Rubus occidentalis||33|
|Canola||Rapeseed oil||mostly Brassica napus||9 – 11|
|Common name||Linnaean name||% ALA|
|Persian walnuts||Juglans regia||6.3|
|Pecan nuts||Carya illinoinensis||0.6|
|Hazel nuts||Corylus avellana||0.1|
Flaxseed (or linseed) (Linum usitatissimum) and its oil are perhaps the most widely available botanical source of the omega−3 fatty acid ALA. Flaxseed oil consists of approximately 55% ALA, which makes it six times richer than most fish oils in omega−3 fatty acids. A portion of this is converted by the body to EPA and DHA, though the actual converted percentage may differ between men and women.
In 2013 Rothamsted Research in the UK reported they had developed a genetically modified form of the plant Camelina that produced EPA and DHA. Oil from the seeds of this plant contained on average 11% EPA and 8% DHA in one development and 24% EPA in another.
Eggs produced by hens fed a diet of greens and insects contain higher levels of omega−3 fatty acids than those produced by chickens fed corn or soybeans. In addition to feeding chickens insects and greens, fish oils may be added to their diets to increase the omega−3 fatty acid concentrations in eggs.
The addition of flax and canola seeds to the diets of chickens, both good sources of alpha-linolenic acid, increases the omega−3 content of the eggs, predominantly DHA.
The addition of green algae or seaweed to the diets boosts the content of DHA and EPA, which are the forms of omega−3 approved by the FDA for medical claims. A common consumer complaint is "Omega−3 eggs can sometimes have a fishy taste if the hens are fed marine oils".
Omega−3 fatty acids are formed in the chloroplasts of green leaves and algae. While seaweeds and algae are the source of omega−3 fatty acids present in fish, grass is the source of omega−3 fatty acids present in grass fed animals. When cattle are taken off omega−3 fatty acid rich grass and shipped to a feedlot to be fattened on omega−3 fatty acid deficient grain, they begin losing their store of this beneficial fat. Each day that an animal spends in the feedlot, the amount of omega−3 fatty acids in its meat is diminished.
In a 2009 joint study by the USDA and researchers at Clemson University in South Carolina, grass-fed beef was compared with grain-finished beef. The researchers found that grass-finished beef is higher in moisture content, 42.5% lower total lipid content, 54% lower in total fatty acids, 54% higher in beta-carotene, 288% higher in vitamin E (alpha-tocopherol), higher in the B-vitamins thiamin and riboflavin, higher in the minerals calcium, magnesium, and potassium, 193% higher in total omega−3s, 117% higher in CLA (cis-9, trans-11 octadecenoic acid, a conjugated linoleic acid, which is a potential cancer fighter), 90% higher in vaccenic acid (which can be transformed into CLA), lower in the saturated fats, and has a healthier ratio of omega−6 to omega−3 fatty acids (1.65 vs 4.84). Protein and cholesterol content were equal.
Seal oil is a source of EPA, DPA, and DHA. According to Health Canada, it helps to support the development of the brain, eyes, and nerves in children up to 12 years of age. Like all seal products, it is not allowed to be imported into the European Union.
A trend in the early 21st century was to fortify food with omega−3 fatty acids. The microalgae Crypthecodinium cohnii and Schizochytrium are rich sources of DHA, but not EPA, and can be produced commercially in bioreactors for use as food additives. Oil from brown algae (kelp) is a source of EPA. The alga Nannochloropsis also has high levels of EPA.
- "Office of Dietary Supplements - Omega-3 Fatty Acids". ods.od.nih.gov. Retrieved 2019-03-22.
- "Essential Fatty Acids". Micronutrient Information Center, Oregon State University, Corvallis, OR. May 2014. Retrieved 24 May 2017.
- Scorletti E, Byrne CD (2013). "Omega-3 fatty acids, hepatic lipid metabolism, and nonalcoholic fatty liver disease". Annual Review of Nutrition. 33 (1): 231–48. doi:10.1146/annurev-nutr-071812-161230. PMID 23862644.
- "Omega-3 Fatty Acids — Health Professional Fact Sheet". US National Institutes of Health, Office of Dietary Supplements. 2 November 2016. Retrieved 5 April 2017.
- Freemantle E, Vandal M, Tremblay-Mercier J, Tremblay S, Blachère JC, Bégin ME, et al. (September 2006). "Omega-3 fatty acids, energy substrates, and brain function during aging". Prostaglandins, Leukotrienes, and Essential Fatty Acids. 75 (3): 213–20. doi:10.1016/j.plefa.2006.05.011. PMID 16829066.
- Chaiyasit W, Elias RJ, McClements DJ, Decker EA (2007). "Role of physical structures in bulk oils on lipid oxidation". Critical Reviews in Food Science and Nutrition. 47 (3): 299–317. doi:10.1080/10408390600754248. PMID 17453926. S2CID 10190504.
- Rizos EC, Ntzani EE, Bika E, Kostapanos MS, Elisaf MS (September 2012). "Association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events: a systematic review and meta-analysis". JAMA. 308 (10): 1024–33. doi:10.1001/2012.jama.11374. PMID 22968891.
- MacLean CH, Newberry SJ, Mojica WA, Khanna P, Issa AM, Suttorp MJ, et al. (January 2006). "Effects of omega-3 fatty acids on cancer risk: a systematic review". JAMA. 295 (4): 403–15. doi:10.1001/jama.295.4.403. hdl:10919/79706. PMID 16434631.
- Aung T, Halsey J, Kromhout D, Gerstein HC, Marchioli R, Tavazzi L, et al. (March 2018). "Associations of Omega-3 Fatty Acid Supplement Use With Cardiovascular Disease Risks: Meta-analysis of 10 Trials Involving 77 917 Individuals". JAMA Cardiology. 3 (3): 225–234. doi:10.1001/jamacardio.2017.5205. PMC 5885893. PMID 29387889.
- Grey A, Bolland M (March 2014). "Clinical trial evidence and use of fish oil supplements". JAMA Internal Medicine. 174 (3): 460–2. doi:10.1001/jamainternmed.2013.12765. PMID 24352849.
- Ratnayake WM, Galli C (2009). "Fat and fatty acid terminology, methods of analysis and fat digestion and metabolism: a background review paper". Annals of Nutrition & Metabolism. 55 (1–3): 8–43. doi:10.1159/000228994. PMID 19752534.
- Rizos EC, Elisaf MS (June 2017). "Does Supplementation with Omega-3 PUFAs Add to the Prevention of Cardiovascular Disease?". Current Cardiology Reports. 19 (6): 47. doi:10.1007/s11886-017-0856-8. PMID 28432658. S2CID 23585060.
- Sala-Vila A, Calder PC (October–November 2011). "Update on the relationship of fish intake with prostate, breast, and colorectal cancers". Critical Reviews in Food Science and Nutrition. 51 (9): 855–71. doi:10.1080/10408398.2010.483527. PMID 21888535. S2CID 25733429.
- Zheng JS, Hu XJ, Zhao YM, Yang J, Li D (June 2013). "Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies". BMJ. 346 (jun27 5): f3706. doi:10.1136/bmj.f3706. PMID 23814120.
- Heinze VM, Actis AB (February 2012). "Dietary conjugated linoleic acid and long-chain n-3 fatty acids in mammary and prostate cancer protection: a review". International Journal of Food Sciences and Nutrition. 63 (1): 66–78. doi:10.3109/09637486.2011.598849. PMID 21762028. S2CID 21614046.
- Hooper L, Thompson RL, Harrison RA, Summerbell CD, Ness AR, Moore HJ, et al. (April 2006). "Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review". BMJ. 332 (7544): 752–60. doi:10.1136/bmj.38755.366331.2F. PMC 1420708. PMID 16565093.
- Chua ME, Sio MC, Sorongon MC, Morales ML (May–June 2013). "The relevance of serum levels of long chain omega-3 polyunsaturated fatty acids and prostate cancer risk: A meta-analysis". Canadian Urological Association Journal. 7 (5–6): E333-43. doi:10.5489/cuaj.1056. PMC 3668400. PMID 23766835.
- Colomer R, Moreno-Nogueira JM, García-Luna PP, García-Peris P, García-de-Lorenzo A, Zarazaga A, et al. (May 2007). "N-3 fatty acids, cancer and cachexia: a systematic review of the literature". The British Journal of Nutrition. 97 (5): 823–31. doi:10.1017/S000711450765795X. PMID 17408522.
- Kwak SM, Myung SK, Lee YJ, Seo HG (May 2012). "Efficacy of omega-3 fatty acid supplements (eicosapentaenoic acid and docosahexaenoic acid) in the secondary prevention of cardiovascular disease: a meta-analysis of randomized, double-blind, placebo-controlled trials". Archives of Internal Medicine. 172 (9): 686–94. doi:10.1001/archinternmed.2012.262. PMID 22493407.
- Billman GE (October 2013). "The effects of omega-3 polyunsaturated fatty acids on cardiac rhythm: a critical reassessment". Pharmacology & Therapeutics. 140 (1): 53–80. doi:10.1016/j.pharmthera.2013.05.011. PMID 23735203.
- Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, et al. (July 2018). "Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease". The Cochrane Database of Systematic Reviews. 7: CD003177. doi:10.1002/14651858.CD003177.pub3. PMC 6513557. PMID 30019766.
- Casula M, Soranna D, Catapano AL, Corrao G (August 2013). "Long-term effect of high dose omega-3 fatty acid supplementation for secondary prevention of cardiovascular outcomes: A meta-analysis of randomized, placebo controlled trials [corrected]". Atherosclerosis. Supplements. 14 (2): 243–51. doi:10.1016/S1567-5688(13)70005-9. PMID 23958480.
- Health Watch, Harvard (April 2019). "Should you be taking an omega-3 supplement?". Harvard Health Publishing, Harvard Medical School. Retrieved 2 June 2020.
- Delgado-Lista J, Perez-Martinez P, Lopez-Miranda J, Perez-Jimenez F (June 2012). "Long chain omega-3 fatty acids and cardiovascular disease: a systematic review". The British Journal of Nutrition. 107 Suppl 2: S201-13. doi:10.1017/S0007114512001596. PMID 22591894.
- Kotwal S, Jun M, Sullivan D, Perkovic V, Neal B (November 2012). "Omega 3 Fatty acids and cardiovascular outcomes: systematic review and meta-analysis". Circulation: Cardiovascular Quality and Outcomes. 5 (6): 808–18. doi:10.1161/CIRCOUTCOMES.112.966168. PMID 23110790.
- "Omega-3 acid ethyl esters - containing medicinal products for oral in use in secondary prevention after myocardial infarction". European Medicines Agency. 6 June 2019.
- Miller PE, Van Elswyk M, Alexander DD (July 2014). "Long-chain omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid and blood pressure: a meta-analysis of randomized controlled trials". American Journal of Hypertension. 27 (7): 885–96. doi:10.1093/ajh/hpu024. PMC 4054797. PMID 24610882.
- Morris MC, Sacks F, Rosner B (August 1993). "Does fish oil lower blood pressure? A meta-analysis of controlled trials". Circulation. 88 (2): 523–33. doi:10.1161/01.CIR.88.2.523. PMID 8339414.
- Mori TA, Bao DQ, Burke V, Puddey IB, Beilin LJ (August 1999). "Docosahexaenoic acid but not eicosapentaenoic acid lowers ambulatory blood pressure and heart rate in humans". Hypertension. 34 (2): 253–60. doi:10.1161/01.HYP.34.2.253. PMID 10454450.
- Weintraub HS (November 2014). "Overview of prescription omega-3 fatty acid products for hypertriglyceridemia". Postgraduate Medicine. 126 (7): 7–18. doi:10.3810/pgm.2014.11.2828. PMID 25387209. S2CID 12524547.
- Wu L, Parhofer KG (December 2014). "Diabetic dyslipidemia". Metabolism. 63 (12): 1469–79. doi:10.1016/j.metabol.2014.08.010. PMID 25242435.
- Miller M, Stone NJ, Ballantyne C, Bittner V, Criqui MH, Ginsberg HN, et al. (May 2011). "Triglycerides and cardiovascular disease: a scientific statement from the American Heart Association". Circulation. 123 (20): 2292–333. doi:10.1161/CIR.0b013e3182160726. PMID 21502576.
- Skulas-Ray AC, Wilson PW, Harris WS, Brinton EA, Kris-Etherton PM, Richter CK, et al. (September 2019). "Omega-3 Fatty Acids for the Management of Hypertriglyceridemia: A Science Advisory From the American Heart Association". Circulation. 140 (12): e673–e691. doi:10.1161/CIR.0000000000000709. PMID 31422671.
- Wang C, Harris WS, Chung M, Lichtenstein AH, Balk EM, Kupelnick B, et al. (July 2006). "n-3 Fatty acids from fish or fish-oil supplements, but not alpha-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review". The American Journal of Clinical Nutrition. 84 (1): 5–17. doi:10.1093/ajcn/84.1.5. PMID 16825676.
- Larsson SC (February 2013). "Dietary fats and other nutrients on stroke". Current Opinion in Lipidology. 24 (1): 41–8. doi:10.1097/mol.0b013e3283592eea. PMID 23123763. S2CID 12666025.
- Robinson LE, Mazurak VC (April 2013). "N-3 polyunsaturated fatty acids: relationship to inflammation in healthy adults and adults exhibiting features of metabolic syndrome". Lipids. 48 (4): 319–32. doi:10.1007/s11745-013-3774-6. PMID 23456976. S2CID 4005634.
- Li K, Huang T, Zheng J, Wu K, Li D (February 2014). "Effect of marine-derived n-3 polyunsaturated fatty acids on C-reactive protein, interleukin 6 and tumor necrosis factor α: a meta-analysis". PLOS ONE. 9 (2): e88103. Bibcode:2014PLoSO...988103L. doi:10.1371/journal.pone.0088103. PMC 3914936. PMID 24505395.
- Miles EA, Calder PC (June 2012). "Influence of marine n-3 polyunsaturated fatty acids on immune function and a systematic review of their effects on clinical outcomes in rheumatoid arthritis". The British Journal of Nutrition. 107 Suppl 2 (S2): S171-84. doi:10.1017/S0007114512001560. PMID 22591891.
- "Herbal Remedies, Supplements & Acupuncture for Arthritis - Supplements for arthritis". American College of Rheumatology. June 2018. Retrieved 6 April 2019.
- "Rheumatoid Arthritis: In Depth". National Center for Complementary and Alternative Medicine. January 2019. Retrieved 6 April 2019.
- Levy SE, Hyman SL (2005). "Novel treatments for autistic spectrum disorders". Mental Retardation and Developmental Disabilities Research Reviews. 11 (2): 131–42. doi:10.1002/mrdd.20062. PMID 15977319.
- Richardson AJ (April 2006). "Omega-3 fatty acids in ADHD and related neurodevelopmental disorders". International Review of Psychiatry. 18 (2): 155–72. doi:10.1080/09540260600583031. PMID 16777670. S2CID 20262302.
- Bloch MH, Qawasmi A (October 2011). "Omega-3 fatty acid supplementation for the treatment of children with attention-deficit/hyperactivity disorder symptomatology: systematic review and meta-analysis". Journal of the American Academy of Child and Adolescent Psychiatry. 50 (10): 991–1000. doi:10.1016/j.jaac.2011.06.008. PMC 3625948. PMID 21961774.
- Gillies D, Sinn JK, Lad SS, Leach MJ, Ross MJ (July 2012). "Polyunsaturated fatty acids (PUFA) for attention deficit hyperactivity disorder (ADHD) in children and adolescents". The Cochrane Database of Systematic Reviews. 7 (7): CD007986. doi:10.1002/14651858.CD007986.pub2. PMC 6599878. PMID 22786509.
- Tan ML, Ho JJ, Teh KH (December 2012). Tan ML (ed.). "Polyunsaturated fatty acids (PUFAs) for children with specific learning disorders". The Cochrane Database of Systematic Reviews. 12: CD009398. doi:10.1002/14651858.CD009398.pub2. PMID 23235675.
- Ortega RM, Rodríguez-Rodríguez E, López-Sobaler AM (June 2012). "Effects of omega 3 fatty acids supplementation in behavior and non-neurodegenerative neuropsychiatric disorders". The British Journal of Nutrition. 107 Suppl 2: S261-70. doi:10.1017/S000711451200164X. PMID 22591900.
- Secher NJ (2007). "Does fish oil prevent preterm birth?". Journal of Perinatal Medicine. 35 Suppl 1: S25-7. doi:10.1515/JPM.2007.033. PMID 17302537. S2CID 201096005.
- Jensen CL (June 2006). "Effects of n-3 fatty acids during pregnancy and lactation". The American Journal of Clinical Nutrition. 83 (6 Suppl): 1452S–1457S. doi:10.1093/ajcn/83.6.1452S. PMID 16841854.
- "Omega−3 long chain polyunsaturated fatty acids to prevent preterm birth: a meta-analysis of randomized controlled trials". www.crd.york.ac.uk. Retrieved 2016-03-01.
- Middleton P, Gomersall JC, Gould JF, Shepherd E, Olsen SF, Makrides M (November 2018). "Omega-3 fatty acid addition during pregnancy". The Cochrane Database of Systematic Reviews. 11: CD003402. doi:10.1002/14651858.cd003402.pub3. PMC 6516961. PMID 30480773.
- Makrides M, Best K, Yelland L, McPhee A, Zhou S, Quinlivan J, et al. (September 2019). "A Randomized Trial of Prenatal n-3 Fatty Acid Supplementation and Preterm Delivery". The New England Journal of Medicine. 381 (11): 1035–1045. doi:10.1056/NEJMoa1816832. PMID 31509674.
- Perica MM, Delas I (August 2011). "Essential fatty acids and psychiatric disorders". Nutrition in Clinical Practice. 26 (4): 409–25. doi:10.1177/0884533611411306. PMID 21775637.
- Firth, Joseph; Teasdale, Scott B.; Allott, Kelly; Siskind, Dan; Marx, Wolfgang; Cotter, Jack; Veronese, Nicola; Schuch, Felipe; Smith, Lee; Solmi, Marco; Carvalho, André F. (2019-09-09). "The efficacy and safety of nutrient supplements in the treatment of mental disorders: a meta‐review of meta‐analyses of randomized controlled trials". World Psychiatry. 18 (3): 308–324. doi:10.1002/wps.20672. ISSN 1723-8617. PMC 6732706. PMID 31496103.
- Guu, Ta-Wei; Su, Kuan-Pin (2019-11-19). "Reply to the Letter to the Editor: Response to "International Society for Nutritional Psychiatry Research Practice Guidelines for Omega-3 Fatty Acids in the Treatment of Major Depressive Disorder" by Guu et al. (2019)". Psychotherapy and Psychosomatics. 89 (1): 49. doi:10.1159/000504232. ISSN 0033-3190. PMID 31743919. S2CID 208187146.
- Ruxton CH, Calder PC, Reed SC, Simpson MJ (June 2005). "The impact of long-chain n-3 polyunsaturated fatty acids on human health". Nutrition Research Reviews. 18 (1): 113–29. doi:10.1079/nrr200497. PMID 19079899.
- Montgomery P, Richardson AJ (April 2008). "Omega-3 fatty acids for bipolar disorder". The Cochrane Database of Systematic Reviews (2): CD005169. doi:10.1002/14651858.CD005169.pub2. PMID 18425912.
- Sanhueza C, Ryan L, Foxcroft DR (February 2013). "Diet and the risk of unipolar depression in adults: systematic review of cohort studies". Journal of Human Nutrition and Dietetics. 26 (1): 56–70. doi:10.1111/j.1365-277X.2012.01283.x. PMID 23078460.
- Appleton KM, Rogers PJ, Ness AR (March 2010). "Updated systematic review and meta-analysis of the effects of n-3 long-chain polyunsaturated fatty acids on depressed mood". The American Journal of Clinical Nutrition. 91 (3): 757–70. doi:10.3945/ajcn.2009.28313. PMID 20130098.
- Bloch MH, Hannestad J (December 2012). "Omega-3 fatty acids for the treatment of depression: systematic review and meta-analysis". Molecular Psychiatry. 17 (12): 1272–82. doi:10.1038/mp.2011.100. PMC 3625950. PMID 21931319.
- Stafford MR, Jackson H, Mayo-Wilson E, Morrison AP, Kendall T (January 2013). "Early interventions to prevent psychosis: systematic review and meta-analysis". BMJ. 346: f185. doi:10.1136/bmj.f185. PMC 3548617. PMID 23335473.
- Cederholm T, Palmblad J (March 2010). "Are omega-3 fatty acids options for prevention and treatment of cognitive decline and dementia?". Current Opinion in Clinical Nutrition and Metabolic Care. 13 (2): 150–5. doi:10.1097/MCO.0b013e328335c40b. PMID 20019606. S2CID 46142968.
- Mazereeuw G, Lanctôt KL, Chau SA, Swardfager W, Herrmann N (July 2012). "Effects of ω-3 fatty acids on cognitive performance: a meta-analysis". Neurobiology of Aging. 33 (7): 1482.e17–29. doi:10.1016/j.neurobiolaging.2011.12.014. PMID 22305186. S2CID 2603173.
- Chew EY, Clemons TE, Agrón E, Launer LJ, Grodstein F, Bernstein PS (August 2015). "Effect of Omega-3 Fatty Acids, Lutein/Zeaxanthin, or Other Nutrient Supplementation on Cognitive Function: The AREDS2 Randomized Clinical Trial". JAMA. 314 (8): 791–801. doi:10.1001/jama.2015.9677. PMC 5369607. PMID 26305649.
- Forbes SC, Holroyd-Leduc JM, Poulin MJ, Hogan DB (December 2015). "Effect of Nutrients, Dietary Supplements and Vitamins on Cognition: a Systematic Review and Meta-Analysis of Randomized Controlled Trials". Canadian Geriatrics Journal. 18 (4): 231–45. doi:10.5770/cgj.18.189. PMC 4696451. PMID 26740832.
- Bradbury J (May 2011). "Docosahexaenoic acid (DHA): an ancient nutrient for the modern human brain". Nutrients. 3 (5): 529–54. doi:10.3390/nu3050529. PMC 3257695. PMID 22254110.
- Harris WS, Baack ML (January 2015). "Beyond building better brains: bridging the docosahexaenoic acid (DHA) gap of prematurity". Journal of Perinatology. 35 (1): 1–7. doi:10.1038/jp.2014.195. PMC 4281288. PMID 25357095.
- Hüppi PS (March 2008). "Nutrition for the brain: commentary on the article by Isaacs et al. on page 308" (PDF). Pediatric Research. 63 (3): 229–31. doi:10.1203/pdr.0b013e318168c6d1. PMID 18287959. S2CID 6564743.
- Lohner S, Decsi T. Role of Long-Chain Polyunsaturated Fatty Acids in the Prevention and Treatment of Atopic Diseases. In: Polyunsaturated Fatty Acids: Sources, Antioxidant Properties and Health Benefits (edited by: Angel Catalá). NOVA Publishers. 2013. Chapter 11, pp. 1–24. (ISBN 978-1-62948-151-7)
- Lohner S, Fekete K, Decsi T (July 2013). "Lower n-3 long-chain polyunsaturated fatty acid values in patients with phenylketonuria: a systematic review and meta-analysis". Nutrition Research. 33 (7): 513–20. doi:10.1016/j.nutres.2013.05.003. PMID 23827125.
- Muley P, Shah M, Muley A (2015). "Omega-3 Fatty Acids Supplementation in Children to Prevent Asthma: Is It Worthy?-A Systematic Review and Meta-Analysis". Journal of Allergy. 2015: 312052. doi:10.1155/2015/312052. PMC 4556859. PMID 26357518.
- "Omega−3 Fatty Acids: An Essential Contribution". TH Chan School of Public Health, Harvard University, Boston. 2017.
- "Sodium-dependent lysophosphatidylcholine symporter 1". UniProt. Retrieved 2 April 2016.
- Nguyen LN, Ma D, Shui G, Wong P, Cazenave-Gassiot A, Zhang X, et al. (May 2014). "Mfsd2a is a transporter for the essential omega-3 fatty acid docosahexaenoic acid". Nature. 509 (7501): 503–6. Bibcode:2014Natur.509..503N. doi:10.1038/nature13241. PMID 24828044. S2CID 4462512.
- van West D, Maes M (February 2003). "Polyunsaturated fatty acids in depression". Acta Neuropsychiatrica. 15 (1): 15–21. doi:10.1034/j.1601-5215.2003.00004.x. PMID 26984701.
- Bergstroem S, Danielsson H, Klenberg D, Samuelsson B (November 1964). "The Enzymatic Conversion of Essential Fatty Acids into Prostaglandins" (PDF). The Journal of Biological Chemistry. 239: PC4006-8. PMID 14257636.
- Lands WE (May 1992). "Biochemistry and physiology of n-3 fatty acids". FASEB Journal. 6 (8): 2530–6. doi:10.1096/fasebj.6.8.1592205. PMID 1592205. S2CID 24182617.
- Kuda O (May 2017). "Bioactive metabolites of docosahexaenoic acid". Biochimie. 136: 12–20. doi:10.1016/j.biochi.2017.01.002. PMID 28087294.
- Gerster H (1998). "Can adults adequately convert alpha-linolenic acid (18:3n-3) to eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)?". International Journal for Vitamin and Nutrition Research. Internationale Zeitschrift für Vitamin- und Ernahrungsforschung. Journal International de Vitaminologie et de Nutrition. 68 (3): 159–73. PMID 9637947.
- Brenna JT (March 2002). "Efficiency of conversion of alpha-linolenic acid to long chain n-3 fatty acids in man". Current Opinion in Clinical Nutrition and Metabolic Care. 5 (2): 127–32. doi:10.1097/00075197-200203000-00002. PMID 11844977.
- Burdge GC, Calder PC (September 2005). "Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults". Reproduction, Nutrition, Development. 45 (5): 581–97. doi:10.1051/rnd:2005047. PMID 16188209.
- Lohner S, Fekete K, Marosvölgyi T, Decsi T (2013). "Gender differences in the long-chain polyunsaturated fatty acid status: systematic review of 51 publications". Annals of Nutrition & Metabolism. 62 (2): 98–112. doi:10.1159/000345599. PMID 23327902.
- Simopoulos AP (June 2008). "The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases". Experimental Biology and Medicine. 233 (6): 674–88. doi:10.3181/0711-MR-311. PMID 18408140. S2CID 9044197.
- Griffin BA (February 2008). "How relevant is the ratio of dietary n-6 to n-3 polyunsaturated fatty acids to cardiovascular disease risk? Evidence from the OPTILIP study". Current Opinion in Lipidology. 19 (1): 57–62. doi:10.1097/MOL.0b013e3282f2e2a8. PMID 18196988. S2CID 13058827.
- "Essential Fatty Acids-Metabolism and Bioavailability". Micronutrient Information Center, Oregon State University. May 2014.
- "Conversion Efficiency of ALA to DHA in Humans". Retrieved 21 October 2007.
- "Women have better ALA conversion efficiency". DHA EPA omega−3 Institute. Retrieved 21 July 2015.
- Goyens PL, Spilker ME, Zock PL, Katan MB, Mensink RP (July 2006). "Conversion of alpha-linolenic acid in humans is influenced by the absolute amounts of alpha-linolenic acid and linoleic acid in the diet and not by their ratio". The American Journal of Clinical Nutrition. 84 (1): 44–53. doi:10.1093/ajcn/84.1.44. PMID 16825680.
- DeFilippis AP, Sperling LS (March 2006). "Understanding omega-3's" (PDF). American Heart Journal. 151 (3): 564–70. doi:10.1016/j.ahj.2005.03.051. PMID 16504616. Archived from the original (PDF) on 22 October 2007.
- Hofmeijer-Sevink MK, Batelaan NM, van Megen HJ, Penninx BW, Cath DC, van den Hout MA, van Balkom AJ (March 2012). "Clinical relevance of comorbidity in anxiety disorders: a report from the Netherlands Study of Depression and Anxiety (NESDA)". Journal of Affective Disorders. 137 (1–3): 106–12. doi:10.1016/j.jad.2011.12.008. PMID 22240085.
- Willett WC (September 2007). "The role of dietary n-6 fatty acids in the prevention of cardiovascular disease". Journal of Cardiovascular Medicine. 8 Suppl 1: S42-5. doi:10.2459/01.JCM.0000289275.72556.13. PMID 17876199. S2CID 1420490.
- Duckett SK, Neel JP, Fontenot JP, Clapham WM (September 2009). "Effects of winter stocker growth rate and finishing system on: III. Tissue proximate, fatty acid, vitamin, and cholesterol content". Journal of Animal Science. 87 (9): 2961–70. doi:10.2527/jas.2009-1850. PMID 19502506.
- Lands WE (2005). Fish, omega−3 and human health. American Oil Chemists' Society. ISBN 978-1-893997-81-3.
- Simopoulos AP (October 2002). "The importance of the ratio of omega-6/omega-3 essential fatty acids". Biomedicine & Pharmacotherapy. 56 (8): 365–79. doi:10.1016/S0753-3322(02)00253-6. PMID 12442909.
- Daley CA, Abbott A, Doyle P, Nader G, Larson S (2004). "A literature review of the value-added nutrients found in grass-fed beef products". California State University, Chico (College of Agriculture). Archived from the original on 2008-07-06. Retrieved 2008-03-23. Cite journal requires
- Simopoulos AP (September 2003). "Importance of the Ratio of Omega-6/Omega-3 Essential Fatty Acids: Evolutionary Aspects". Omega-6/Omega-3 Essential Fatty Acid Ratio: The Scientific Evidence. World Review of Nutrition and Dietetics. 92. pp. 1–22. doi:10.1159/000073788. ISBN 978-3-8055-7640-6. PMID 14579680.
- Simopoulos AP, Leaf A, Salem N (September 2000). "Workshop statement on the essentiality of and recommended dietary intakes for Omega-6 and Omega-3 fatty acids". Prostaglandins, Leukotrienes, and Essential Fatty Acids. 63 (3): 119–21. doi:10.1054/plef.2000.0176. PMID 10991764.
- Hibbeln JR, Nieminen LR, Blasbalg TL, Riggs JA, Lands WE (June 2006). "Healthy intakes of n-3 and n-6 fatty acids: estimations considering worldwide diversity". The American Journal of Clinical Nutrition. 83 (6 Suppl): 1483S–1493S. doi:10.1093/ajcn/83.6.1483S. PMID 16841858.
- Martina Bavec; Franc Bavec (2006). Organic Production and Use of Alternative Crops. London: Taylor & Francis Ltd. p. 178. ISBN 978-1-4200-1742-7. Retrieved 2013-02-18.
- Erasmus, Udo, Fats and Oils. 1986. Alive books, Vancouver, ISBN 0-920470-16-5 p. 263 (round-number ratio within ranges given.)
- "Oil, vegetable, corn, industrial and retail, all purpose salad or cooking; USDA Nutrient Data, SR-21". Conde Nast. Retrieved 12 April 2014.
- Dusheck J (October 1985). "Fish, Fatty Acids, and Physiology". Science News. 128 (16): 241–56. doi:10.2307/3970056. JSTOR 3970056.
- Holman RT (February 1998). "The slow discovery of the importance of omega 3 essential fatty acids in human health". The Journal of Nutrition. 128 (2 Suppl): 427S–433S. doi:10.1093/jn/128.2.427S. PMID 9478042.
- "FDA announces qualified health claims for omega−3 fatty acids" (Press release). United States Food and Drug Administration. September 8, 2004. Retrieved 2006-07-10.
- Canadian Food Inspection Agency. Acceptable nutrient function claims. Accessed 30 April 2015
- Simopoulos AP (March 2016). "An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity". Nutrients. 8 (3): 128. doi:10.3390/nu8030128. PMC 4808858. PMID 26950145.
- "Fish, Levels of Mercury and Omega−3 Fatty Acids". American Heart Association. Retrieved October 6, 2010.
- Kris-Etherton PM, Harris WS, Appel LJ (November 2002). "Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease". Circulation. 106 (21): 2747–57. CiteSeerX 10.1.1.336.457. doi:10.1161/01.CIR.0000038493.65177.94. PMID 12438303.
- "Omega−3 Centre". Omega−3 sources. Omega−3 Centre. Archived from the original on 2008-07-18. Retrieved 2008-07-27.
- Food and Nutrition Board (2005). Dietary Reference Intakes For Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: Institute of Medicine of the National Academies. pp. 423, 770. ISBN 978-0-309-08537-3. Retrieved 2012-03-06.
- Siscovick DS, Barringer TA, Fretts AM, Wu JH, Lichtenstein AH, Costello RB, et al. (April 2017). "Omega-3 Polyunsaturated Fatty Acid (Fish Oil) Supplementation and the Prevention of Clinical Cardiovascular Disease: A Science Advisory From the American Heart Association". Circulation. 135 (15): e867–e884. doi:10.1161/CIR.0000000000000482. PMC 6903779. PMID 28289069.
- A 2005 corporate test by Consumer Labs of 44 fish oils on the US market found all of the products passed safety standards for potential contaminants.
- "Product Review: Omega−3 Fatty Acids (EPA and DHA) from Fish/Marine Oils". ConsumerLab.com. 2005-03-15. Retrieved 2007-08-14.
- 2005 study by the Food Safety Authority of Ireland: https://www.fsai.ie/uploadedFiles/Dioxins_milk_survey_2005.pdf
- "IFOS Home – The International Fish Oil Standards Program". Archived from the original on 2011-08-21. Retrieved 2011-08-21.
- Shahidi F, Wanasundara UN (1998-06-01). "Omega−3 fatty acid concentrates: nutritional aspects and production technologies". Trends in Food Science & Technology. 9 (6): 230–40. doi:10.1016/S0924-2244(98)00044-2.
- Mozaffarian, Rimm EB (2006). "Fish intake, contaminants, and human health: evaluating the risks and the benefits". Journal of the American Medical Association. 15 (1): 1885–99. doi:10.1001/jama.296.15.1885. ISSN 0098-7484. PMID 17047219.
- Falk-Petersen A, Sargent JR, Henderson J, Hegseth EN, Hop H, Okolodkov YB (1998). "Lipids and fatty acids in ice algae and phytoplankton from the Marginal Ice Zone in the Barents Sea". Polar Biology. 20 (1): 41–47. doi:10.1007/s003000050274. ISSN 0722-4060. S2CID 11027523. INIST:2356641.
- "Farmed fish: a major provider or a major consumer of omega-3 oils?". GLOBEFISH. Food and Agriculture Organization of the United Nations. Retrieved 30 August 2018.
- Innis SM, Rioux FM, Auestad N, Ackman RG (September 1995). "Marine and freshwater fish oil varying in arachidonic, eicosapentaenoic and docosahexaenoic acids differ in their effects on organ lipids and fatty acids in growing rats". The Journal of Nutrition. 125 (9): 2286–93. doi:10.1093/jn/125.9.2286. PMID 7666244.
- Lawson LD, Hughes BG (October 1988). "Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacylglycerols or fish oil ethyl esters co-ingested with a high-fat meal". Biochemical and Biophysical Research Communications. 156 (2): 960–3. doi:10.1016/S0006-291X(88)80937-9. PMID 2847723.
- Beckermann B, Beneke M, Seitz I (June 1990). "[Comparative bioavailability of eicosapentaenoic acid and docasahexaenoic acid from triglycerides, free fatty acids and ethyl esters in volunteers]". Arzneimittel-Forschung (in German). 40 (6): 700–4. PMID 2144420.
- Tur JA, Bibiloni MM, Sureda A, Pons A (June 2012). "Dietary sources of omega 3 fatty acids: public health risks and benefits". The British Journal of Nutrition. 107 Suppl 2 (Suppl 2): S23-52. doi:10.1017/S0007114512001456. PMID 22591897.
- Ulven SM, Kirkhus B, Lamglait A, Basu S, Elind E, Haider T, et al. (January 2011). "Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA, in healthy volunteers". Lipids. 46 (1): 37–46. doi:10.1007/s11745-010-3490-4. PMC 3024511. PMID 21042875.
- Atkinson A, Siegel V, Pakhomov E, Rothery P (November 2004). "Long-term decline in krill stock and increase in salps within the Southern Ocean". Nature. 432 (7013): 100–3. Bibcode:2004Natur.432..100A. doi:10.1038/nature02996. PMID 15525989. S2CID 4397262.
- Orr A (2014). "Malnutrition behind whale strandings". Stuff, Fairfax New Zealand Limited. Retrieved 8 August 2015.
- "Krill fisheries and sustainability". Commission for the Conservation of Antarctic Marine Living Resources, Tasmania, Australia. 2015. Retrieved 8 August 2015.
- Köhler, Anton; Sarkkinen, Essi; Tapola, Niina; Niskanen, Tarja; Bruheim, Inge (2015-01-01). "Bioavailability of fatty acids from krill oil, krill meal and fish oil in healthy subjects–a randomized, single-dose, cross-over trial". Lipids in Health and Disease. 14: 19. doi:10.1186/s12944-015-0015-4. ISSN 1476-511X. PMC 4374210. PMID 25884846.
- Saw, Constance Lay Lay; Yang, Anne Yuqing; Guo, Yue; Kong, Ah-Ng Tony (2013-12-01). "Astaxanthin and omega-3 fatty acids individually and in combination protect against oxidative stress via the Nrf2-ARE pathway". Food and Chemical Toxicology. 62: 869–875. doi:10.1016/j.fct.2013.10.023. ISSN 1873-6351. PMID 24157545.
- Barros, Marcelo P.; Poppe, Sandra C.; Bondan, Eduardo F. (2014-03-24). "Neuroprotective Properties of the Marine Carotenoid Astaxanthin and Omega-3 Fatty Acids, and Perspectives for the Natural Combination of Both in Krill Oil". Nutrients. 6 (3): 1293–1317. doi:10.3390/nu6031293. ISSN 2072-6643. PMC 3967194. PMID 24667135.
- Zimmer, Carl (September 17, 2015). "Inuit Study Adds Twist to Omega-3 Fatty Acids' Health Story". The New York Times. Retrieved October 11, 2015.
- O'Connor, Anahad (March 30, 2015). "Fish Oil Claims Not Supported by Research". The New York Times. Retrieved October 11, 2015.
- "Seed Oil Fatty Acids – SOFA Database Retrieval". In German. Google translation
- "WWW.osel.co.nz - 1st Domains" (PDF). Archived from the original (PDF) on 2012-01-31. Retrieved 2012-07-21.
- "WWW.osel.co.nz - 1st Domains" (PDF). Archived from the original (PDF) on 2013-02-05. Retrieved 2012-07-21.
- Soltana H, Tekaya M, Amri Z, El-Gharbi S, Nakbi A, Harzallah A, et al. (April 2016). "Characterization of fig achenes' oil of Ficus carica grown in Tunisia". Food Chemistry. 196: 1125–30. doi:10.1016/j.foodchem.2015.10.053. PMID 26593597.
- Wilkinson J. "Nut Grower's Guide: The Complete Handbook for Producers and Hobbyists" (PDF). Retrieved 21 October 2007.
- Thomas Bartram (September 2002). Bartram's Encyclopedia of Herbal Medicine: The Definitive Guide to the Herbal Treatments of Diseases. Da Capo Press. p. 271. ISBN 978-1-56924-550-7.
- Decsi T, Kennedy K (December 2011). "Sex-specific differences in essential fatty acid metabolism". The American Journal of Clinical Nutrition. 94 (6 Suppl): 1914S–1919S. doi:10.3945/ajcn.110.000893. PMID 22089435.
- Ruiz-Lopez N, Haslam RP, Napier JA, Sayanova O (January 2014). "Successful high-level accumulation of fish oil omega-3 long-chain polyunsaturated fatty acids in a transgenic oilseed crop". The Plant Journal. 77 (2): 198–208. doi:10.1111/tpj.12378. PMC 4253037. PMID 24308505.
- Coghlan, Andy (4 January 2014) "Designed plant oozes vital fish oils" New Scientist, volume 221, issue 2950, p. 12
- "How Omega-6s Usurped Omega-3s In US Diet". Medical News Today. Retrieved Apr 28, 2020.
- Trebunová A, Vasko L, Svedová M, Kastel' R, Tucková M, Mach P (July 2007). "The influence of omega-3 polyunsaturated fatty acids feeding on composition of fatty acids in fatty tissues and eggs of laying hens". DTW. Deutsche Tierarztliche Wochenschrift. 114 (7): 275–9. PMID 17724936.
- Cherian G, Sim JS (April 1991). "Effect of feeding full fat flax and canola seeds to laying hens on the fatty acid composition of eggs, embryos, and newly hatched chicks". Poultry Science. 70 (4): 917–22. doi:10.3382/ps.0700917.
- Sterling C (2010-06-03). "Washington Post's Egg Taste Test Says Homegrown And Factory Eggs Taste The Same [UPDATED, POLL]". Huffingtonpost.com. Retrieved 2011-01-03.
- Garton GA (August 1960). "Fatty acid composition of the lipids of pasture grasses". Nature. 187 (4736): 511–2. Bibcode:1960Natur.187..511G. doi:10.1038/187511b0. PMID 13826699. S2CID 4296061.
- Duckett SK, Wagner DG, Yates LD, Dolezal HG, May SG (August 1993). "Effects of time on feed on beef nutrient composition". Journal of Animal Science. 71 (8): 2079–88. doi:10.2527/1993.7182079x. PMID 8376232.
- Azcona JO, Schang MJ, Garcia PT, Gallinger C, Ayerza Jr R, Coates W (2008). "Omega−3 enriched broiler meat: The influence of dietary alpha-linolenic omega−3 fatty acid sources on growth, performance and meat fatty acid composition". Canadian Journal of Animal Science. 88 (2): 257–69. doi:10.4141/CJAS07081.
- "Gourmet Game – Amazing Nutrition Facts". 2019-05-31. Archived from the original on 2009-03-01.
- "Natural Health Product Monograph – Seal Oil". Health Canada. June 22, 2009. Archived from the original on 2012-03-19. Retrieved June 20, 2012.
- European Parliament (9 November 2009). "MEPs adopt strict conditions for the placing on the market of seal products in the European Union". Hearings. European Parliament. Retrieved 12 March 2010.
- Ganesan B, Brothersen C, McMahon DJ (2014). "Fortification of foods with omega-3 polyunsaturated fatty acids". Critical Reviews in Food Science and Nutrition. 54 (1): 98–114. doi:10.1080/10408398.2011.578221. PMID 24188235. S2CID 44629122.
- Leslie Beck (9 May 2018). "Omega-3 eggs: healthier choice or marketing gimmick?". The Toronto Globe and Mail. Retrieved 7 March 2019.
- van Ginneken VJ, Helsper JP, de Visser W, van Keulen H, Brandenburg WA (June 2011). "Polyunsaturated fatty acids in various macroalgal species from North Atlantic and tropical seas". Lipids in Health and Disease. 10 (104): 104. doi:10.1186/1476-511X-10-104. PMC 3131239. PMID 21696609.
- Collins ML, Lynch B, Barfield W, Bull A, Ryan AS, Astwood JD (October 2014). "Genetic and acute toxicological evaluation of an algal oil containing eicosapentaenoic acid (EPA) and palmitoleic acid". Food and Chemical Toxicology. 72: 162–8. doi:10.1016/j.fct.2014.07.021. PMID 25057807.
- Allport S (September 2006). The Queen of Fats: Why Omega−3s Were Removed from the Western Diet and What We Can Do to Replace Them. University of California Press. ISBN 978-0-520-24282-1. OCLC 801139991.
- Chow CK (2001). Fatty Acids in Foods and Their Health Implications. New York: Routledge Publishing. OCLC 25508943.
- Clover C (2004). The End of the Line: How overfishing is changing the world and what we eat. London 2004: Ebury Press. ISBN 0-09-189780-7. OCLC 67383509.CS1 maint: location (link)
- Greenberg P (2018). The Omega Principle: Seafood and the Quest for a Long Life and a Healthier Planet. New York: Penguin Press. ISBN 9781594206344. OCLC 1007552654.
- Stoll, Andrew L. (2001). The Omega−3 Connection: how you can restore your body's natural balance and treat depression. Simon & Schuster. ISBN 0-684-87138-6. OCLC 670441405.
- Media related to Omega-3 fatty acids at Wikimedia Commons