Dietary elements (commonly known as dietary minerals or mineral nutrients) are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. The term "dietary mineral" is archaic, as the substances it refers to are chemical elements rather than actual minerals.
Chemical elements in order of abundance in the human body include the seven major dietary elements calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium. Important "trace" or minor dietary elements, necessary for mammalian life, include iron, cobalt, copper, zinc, manganese, molybdenum, iodine, bromine, and selenium (see below for detailed discussion).
Over twenty dietary elements are necessary for mammals, and several more for various other types of life. The total number of chemical elements that are absolutely needed is not known for any organism. Ultratrace amounts of some elements (e.g., boron, chromium) are known to clearly have a role but the exact biochemical nature is unknown, and others (e.g. arsenic, silicon) are suspected to have a role in health, but without proof.
Most chemical elements that enter into the dietary physiology of organisms are in the form of simple compounds. Larger chemical compounds of elements need to be broken down for absorption. Plants absorb dissolved elements in soils, which are subsequently picked up by the herbivores that eat them and so on; the elements move up the food chain. Larger organisms may also consume soil (geophagia) and visit salt licks to obtain limiting dietary elements they are unable to acquire through other components of their diet.
Bacteria play an essential role in the weathering of primary elements that results in the release of nutrients for their own nutrition and for the nutrition of others in the ecological food chain. One element, cobalt, is available for use by animals only after having been processed into complicated molecules (e.g., vitamin B12) by bacteria. Scientists are only recently starting to appreciate the magnitude and role that microorganisms have in the global cycling and formation of biominerals.
Essential chemical elements for mammals
Some sources state that sixteen chemical elements are required to support human biochemical processes by serving structural and functional roles as well as electrolytes: However, as many as 26 elements in total (including the common hydrogen, carbon, nitrogen and oxygen) are suggested to be used by mammals, as a result of studies of biochemical, special uptake, and metabolic handling studies. However, many of these additional elements have no well-defined biochemical function known at present. Most of the known and suggested dietary elements are of relatively low atomic weight, and are reasonably common on land, or at least, common in the ocean (iodine, sodium):
Periodic table highlighting dietary elements
|The four organic basic elements||Quantity elements||Essential trace elements||Possible structural or functional role in mammals|
The following play important roles in biological processes:
|Dietary element||RDA/AI (mg)||Description||Category||High nutrient density
|Sulfur||Relatively large quantities of sulfur are required, but there is no RDA, as the sulfur is obtained from and used for amino acids, and therefore should be adequate in any diet containing enough protein.||(primarily associated with compounds)|
|Potassium||4700 mg||Quantity||A systemic electrolyte and is essential in coregulating ATP with sodium.||Legumes, potato skin, tomatoes, bananas, papayas, lentils, dry beans, whole grains, avocados, yams, soybeans, spinach, chard, sweet potato, turmeric.||hypokalemia||hyperkalemia|
|Chlorine||2300 mg||Quantity||Needed for production of hydrochloric acid in the stomach and in cellular pump functions.||Table salt (sodium chloride) is the main dietary source.||hypochloremia||hyperchloremia|
|Sodium||1500 mg||Quantity||A systemic electrolyte and is essential in coregulating ATP with potassium.||Table salt (sodium chloride, the main source), sea vegetables, milk, and spinach.||hyponatremia||hypernatremia|
|Calcium||1300 mg||Quantity||Needed for muscle, heart and digestive system health, builds bone, supports synthesis and function of blood cells.||Dairy products, eggs, canned fish with bones (salmon, sardines), green leafy vegetables, nuts, seeds, tofu, thyme, oregano, dill, cinnamon.||hypocalcaemia||hypercalcaemia|
|Phosphorus||700 mg||Quantity||A component of bones (see apatite), cells, in energy processing, in DNA and ATP (as phosphate) and many other functions.||Red meat, dairy foods, fish, poultry, bread, rice, oats. In biological contexts, usually seen as phosphate.||hypophosphatemia||hyperphosphatemia|
|Magnesium||420 mg||Quantity||Required for processing ATP and for bones.||Raw nuts, soybeans, cocoa mass, spinach, chard, sea vegetables, tomatoes, halibut, beans, ginger, cumin, cloves.||hypomagnesemia,
|Zinc||11 mg||Trace||Pervasive and required for several enzymes such as carboxypeptidase, liver alcohol dehydrogenase, and carbonic anhydrase.||Calf liver, eggs, dry beans, mushrooms, spinach, asparagus, scallops, red meat, green peas, yogurt, oats, seeds, miso.||zinc deficiency||zinc toxicity|
|Iron||18 mg||Trace||Required for many proteins and enzymes, notably hemoglobin to prevent anemia.||Red meat, fish (tuna, salmon), grains, dry beans, eggs, spinach, chard, turmeric, cumin, parsley, lentils, tofu, asparagus, leafy green vegetables, soybeans, shrimp, beans, tomatoes, olives, and dried fruit.||anemia||iron overload disorder|
|Manganese||2.3 mg||Trace||A cofactor in enzyme functions.||Spelt grain, brown rice, beans, spinach, pineapple, tempeh, rye, soybeans, thyme, raspberries, strawberries, garlic, squash, eggplant, cloves, cinnamon, turmeric.||manganese deficiency||manganism|
Main article: Copper in health
|0.900 mg||Trace||Required component of many redox enzymes, including cytochrome c oxidase.||Mushrooms, spinach, greens, seeds, raw cashews, raw walnuts, tempeh, barley.||copper deficiency||copper toxicity|
|Iodine||0.150 mg||Trace||Required not only for the synthesis of thyroid hormones, thyroxine and triiodothyronine and to prevent goiter, but also, probably as an antioxidant, for extrathyroidal organs as mammary and salivary glands and for gastric mucosa and immune system (thymus):||Sea vegetables, iodized salt, eggs. Alternate but inconsistent sources of iodine: strawberries, mozzarella cheese, yogurt, milk, fish, shellfish.||iodine deficiency||iodism|
|Selenium||0.055 mg||Trace||Essential to activity of antioxidant enzymes like glutathione peroxidase.||Brazil nuts, cold water wild fish (cod, halibut, salmon), tuna, lamb, turkey, calf liver, mustard, mushrooms, barley, cheese, garlic, tofu, seeds.||selenium deficiency||selenosis|
|Molybdenum||0.045 mg||Trace||The oxidases xanthine oxidase, aldehyde oxidase, and sulfite oxidase.||Tomatoes, onions, carrots.||molybdenum deficiency||molybdenum toxicity|
|Cobalt||Cobalt is required in the synthesis of vitamin B12, but because bacteria are required to synthesize the vitamin, it is usually considered part of vitamin B12 deficiency rather than its own dietary element deficiency.||Cobalt poisoning|
|Bromine||none||Trace||Basement membrane architecture and tissue development.||bromism|
|Arsenic||none||Trace||Essential in rat, hamster, goat and chicken models, but no biochem mechanism known.||arsenic poisoning|
Blood concentrations of dietary elements
Dietary elements are present in a healthy human being's blood at certain mass and molar concentrations. The figure below presents the concentrations of each of the dietary elements discussed in this article, from center-right to the right. Depending on the concentrations, some are in upper part of the picture, while others are in the lower part. The figure includes the relative values of other constituents of blood such as hormones. In the figure, dietary elements are color highlighted in purple.
Dietitians may recommend that dietary elements are best supplied by ingesting specific foods rich with the chemical element(s) of interest. The elements may be naturally present in the food (e.g., calcium in dairy milk) or added to the food (e.g., orange juice fortified with calcium; iodized salt, salt fortified with iodine). Dietary supplements can be formulated to contain several different chemical elements (as compounds), a combination of vitamins and/or other chemical compounds, or a single element (as a compound or mixture of compounds), such as calcium (as carbonate, citrate, etc.) or magnesium (as oxide, etc.), chromium (usually as picolinate) or iron (as bis-glycinate).
The dietary focus on chemical elements derives from an interest in supporting the biochemical reactions of metabolism with the required elemental components. Appropriate intake levels of certain chemical elements have been demonstrated to be required to maintain optimal health. Diet can meet all the body's chemical element requirements, although supplements can be used when some requirements (e.g., calcium, which is found mainly in dairy products) are not adequately met by the diet, or when chronic or acute deficiencies arise from pathology, injury, etc. Research has supported that altering inorganic mineral compounds (carbonates, oxides, etc.) by reacting them with organic ligands (amino acids, organic acids, etc.) improves the bioavailability of the supplemented mineral.
Many elements have been suggested as essential, but such claims have usually not been confirmed. Definitive evidence for efficacy comes from the characterization of a biomolecule containing the element with an identifiable and testable function. One problem with identifying efficacy is that some elements are innocuous at low concentrations and are pervasive (examples: silicon and nickel in solid and dust), so proof of efficacy is lacking because deficiencies are difficult to reproduce.
|Nickel||There have been occasional studies asserting the essentiality of nickel, but it currently has no RDA.||Nickel toxicity|
|Chromium||Chromium has been described as nonessential to mammals. Some role in sugar metabolism in humans has been invoked, but evidence is lacking, despite a market for the supplement chromium picolinate.||Chromium toxicity|
|Fluorine||Fluorine (as Fluoride) is not generally considered an essential element because humans do not require it for growth or to sustain life. However, if one considers the prevention of dental cavities an important criterion in determining essentiality, then fluoride might well be considered an essential trace element. However, recent research indicates that the primary action of fluoride occurs topically (at the surface).||Fluoride poisoning|
|Boron||Boron is an essential plant nutrient, required primarily for maintaining the integrity of cell walls. In animals, supplemental boron has been shown to reduce calcium excretion and activate vitamin D. However, whether these effects were conventionally nutritional, or medicinal, could not be determined.|
|Lithium||It is not known whether lithium has a physiological role in any species, but nutritional studies in mammals have indicated its importance to health, leading to a suggestion that it be classed as an essential trace element with an RDA of 1 mg/day. Observational studies in Japan, reported in 2011, suggested that naturally occurring lithium in drinking water may increase human lifespan.|
|Strontium||Strontium has been found to be involved in the utilization of calcium in the body. It has promoting action on calcium uptake into bone at moderate dietary strontium levels, but a rachitogenic (rickets-producing) action at higher dietary levels.||Rachitogenic|
|Other||Silicon and vanadium have established, albeit specialized, biochemical roles as structural or functional cofactors in other organisms, and are possibly, even probably, used by mammals (including humans). By contrast, tungsten and cadmium have specialized biochemical uses in certain lower organisms, but these elements appear not to be utilized by humans.||Multiple|
Recent studies have shown a tight linkage between living organisms and chemical elements on this planet. This led to the redefinition of minerals as "an element or compound, amorphous or crystalline, formed through 'biogeochemical' processes. The addition of `bio' reflects a greater appreciation, although an incomplete understanding, of the processes of mineral formation by living forms.":621 Biologists and geologists have only recently started to appreciate the magnitude of mineral biogeoengineering. Bacteria have contributed to the formation of minerals for billions of years and critically define the biogeochemical mineral cycles on this planet. Microorganisms can precipitate metals from solution contributing to the formation of ore deposits in addition to their ability to catalyze mineral dissolution, to respire, precipitate, and form minerals.
Most minerals are inorganic in nature. Mineral nutrients refers to the smaller class of minerals that are metabolized for growth, development, and vitality of living organisms. Mineral nutrients are recycled by bacteria that are freely suspended in the vast water columns of the worlds oceans. They absorb dissolved organic matter containing mineral nutrients as they scavenge through the dying individuals that fall out of large phytoplankton blooms. Flagellates are effective bacteriovores and are also commonly found in the marine water column. The flagellates are preyed upon by zooplankton while the phytoplankton concentrates on the larger particulate matter that is suspended in the water column as they are consumed by larger zooplankton, with fish as the top predator. Mineral nutrients cycle through this marine food chain, from bacteria and phytoplankton to flagellates and zooplankton who are then eaten by fish. The bacteria are important in this chain because only they have the physiological ability to absorb the dissolved mineral nutrients from the sea. These recycling principals from marine environments apply to many soil and freshwater ecosystems as well.
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