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In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. Minerals originate in the earth and cannot be made by living organisms. Plants get minerals from soil. Most of the minerals in a human diet come from eating plants and animals or from drinking water. As a group, minerals are one of the four groups of essential nutrients, the others of which are vitamins, essential fatty acids, and essential amino acids.
The five major minerals in the human body are calcium, phosphorus, potassium, sodium, and magnesium. All of the remaining elements in a human body are called "trace elements". The trace elements that have a specific biochemical function in the human body are sulfur, iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine and selenium.
Most chemical elements that are ingested by organisms are in the form of simple compounds. Plants absorb dissolved elements in soils, which are subsequently ingested by the herbivores and omnivores that eat them, and the elements move up the food chain. Larger organisms may also consume soil (geophagia) or use mineral resources, such as salt licks, to obtain limited minerals unavailable through other dietary sources.
Bacteria and fungi 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 other species in the ecological food chain. One element, cobalt, is available for use by animals only after having been processed into complex molecules (e.g., vitamin B12) by bacteria. Minerals are used by animals and microorganisms for the process of mineralizing structures, called "biomineralization", used to construct bones, seashells, eggshells, exoskeletons and mollusc shells.
Essential chemical elements for humans
At least twenty chemical elements are known to be required to support human biochemical processes by serving structural and functional roles as well as electrolytes. However, as many as twenty-nine elements in total (including hydrogen, carbon, nitrogen and oxygen) are suggested to be used by mammals, as inferred by biochemical and uptake studies. Calcium makes up 920 to 1200 mg of adult body weight, with 99% of it contained in bones and teeth. Phosphorus makes up about 1% of a person's body weight. The other major minerals (potassium, sodium, chlorine, sulfur and magnesium) make up only about 0.85% of the weight of the body. Together these eleven chemical elements (H, C, N, O, Ca, P, K, Na, Cl, S, Mg) make up 99.85% of the body. There is not scientific consensus on whether all of the elements in light green in periodic table are essential or not.
Most of the known and suggested mineral nutrients are of relatively low atomic weight, and are reasonably common on land, or, at least, common in the ocean (iodine, sodium):
The four basic organic elements
Suggested function from deprivation effects or active metabolic handling, but no clearly-identified biochemical function in humans
Limited circumstantial evidence for trace benefits or biological action in mammals
No evidence for biological action in mammals, but essential in some lower organisms.
(In the case of lanthanum, the definition of an essential nutrient as being indispensable and irreplaceable is not completely applicable due to the extreme similarity of the lanthanides. Thus Ce, Pr, and Nd may be substituted for La without ill effects for organisms using La, and the smaller Sm, Eu, and Gd may also be similarly substituted but cause slower growth.)
The following play important roles in biological processes:
RDA = Recommended Dietary Allowance; UL = Tolerable Upper Intake Level; Figures shown are for adults age 31-50, male or female neither pregnant nor lactating
|Dietary element||RDA (U.S.) [mg]||UL (U.S. and EU) [mg]||Amount||Category||High nutrient density
|Potassium||4700||NE; NE||Quantity||A systemic electrolyte and is essential in coregulating ATP with sodium||Sweet potato, tomato, potato, beans, lentils, dairy products, seafood, banana, prune, carrot, orange||hypokalemia||hyperkalemia|
|Chlorine||2300||3600; NE||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||2300; NE||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||1200||2500; 2500||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||4000; 4000||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||350; 250||Quantity||Required for processing ATP and for bones||Spinach, legumes, nuts, seeds, whole grains, peanut butter, avocado||hypomagnesemia,
|Iron||18||45; NE||Trace||Required for many proteins and enzymes, notably hemoglobin to prevent anemia||Meat, seafood, nuts, beans, dark chocolate||iron deficiency||iron overload disorder|
|Zinc||11||40; 25||Trace||Pervasive and required for several enzymes such as carboxypeptidase, liver alcohol dehydrogenase, and carbonic anhydrase||Oysters*, red meat, poultry, nuts, whole grains, dairy products||zinc deficiency||zinc toxicity|
|Manganese||2.3||11; NE||Trace||A cofactor in enzyme functions||Grains, legumes, seeds, nuts, leafy vegetables, tea, coffee||manganese deficiency||manganism|
|Copper||0.9||10; 5||Trace||Required component of many redox enzymes, including cytochrome c oxidase||Liver, seafood, oysters, nuts, seeds; some: whole grains, legumes||copper deficiency||copper toxicity|
|Iodine||0.150||1.1; 0.6||Trace||Required for synthesis of thyroid hormones, thyroxine and triiodothyronine and to prevent goiter:||Seaweed (kelp or kombu)*, grains, eggs, iodized salt||iodine deficiency||iodism Hyperthyroidism|
|Chromium||0.035||NE; NE||Trace||Involved in glucose and lipid metabolism, although its mechanisms of action in the body and the amounts needed for optimal health are not well-defined||Broccoli, grape juice (especially red), meat, whole grain products||Chromium deficiency||Chromium toxicity|
|Molybdenum||0.045||2; 0.6||Trace||The oxidases xanthine oxidase, aldehyde oxidase, and sulfite oxidase||Legumes, whole grains, nuts||molybdenum deficiency||molybdenum toxicity|
|Selenium||0.055||0.4; 0.3||Trace||Essential to activity of antioxidant enzymes like glutathione peroxidase||Brazil nuts, seafoods, organ meats, meats, grains, dairy products, eggs||selenium deficiency||selenosis|
|Cobalt||none||NE; NE||Trace||Required in the synthesis of vitamin B12, but because bacteria are required to synthesize the vitamin, it is usually considered part of vitamin B12 which comes from eating animals and animal-sourced foods (eggs...)||Cobalt poisoning|
* One serving of seaweed exceeds the U.S. Tolerable Upper Intake Level (UL) of 1100 μg but not the 3000 μg UL set by Japan.
Blood concentrations of minerals
Minerals 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 chemical 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, minerals are color highlighted in purple.
Dietitians may recommend that minerals 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 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 calcium carbonate, calcium citrate, etc.) or magnesium (as magnesium oxide, etc.), or iron (as ferrous sulfate, iron bis-glycinate, etc.).
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.
Elements considered possibly essential but not confirmed
Many ultratrace 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. Ultratrace elements of some minerals such as silicon and boron are known to have a role but the exact biochemical nature is unknown, and others such as arsenic and chromium are suspected to have a role in health, but with weaker evidence. Chromium is considered and essential mineral by the U.S. Institute of Medicine but not for the European Food Safety Authority, which makes the decisions for the European Union. Roles for trace minerals include enzyme catalysis, attracting substrate molecules, redox reactions, and structural or regulatory effects on protein binding.
|Bromine||Possibly important to basement membrane architecture and tissue development, as a needed catalyst to make collagen IV.||bromism|
|Arsenic||Essential in rat, hamster, goat and chicken models, but no biochemical mechanism known in humans.||arsenic poisoning|
|Nickel||Nickel is an essential component of several enzymes, including urease and hydrogenase. Although not required by humans, some are thought to be required by gut bacteria, such as urease required by some varieties of Bifidobacterium. In humans, nickel may be a cofactor or structural component of certain metalloenzymes involved in hydrolysis, redox rections, and gene expression. Nickel deficiency depressed growth in goats, pigs, and sheep, and diminished circulating thyroid hormone concentration in rats.||Nickel toxicity|
|Fluorine||Fluorine (as fluoride) is not considered an essential element because humans do not require it for growth or to sustain life. Research indicates that the primary dental benefit from fluoride occurs at the surface from topical exposure. Of the minerals in this table, fluoride is the only one for which the U.S. Institute of Medicine has established an Adequate Intake||Fluoride poisoning|
|Boron||Boron is an essential plant nutrient, required primarily for maintaining the integrity of cell walls. Boron has been shown to be essential to complete the life cycle in representatives of all phylogenetic kingdoms, including the model species danio rerio (zebrafish) and Xenopus laevis (African clawed frog). In animals, supplemental boron has been shown to reduce calcium excretion and activate vitamin D.||Nontoxic|
|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.||Lithium toxicity|
|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 (causing Rickets)|
|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, lanthanum, and cadmium have specialized biochemical uses in certain lower organisms, but these elements appear not to be utilized by humans. Other elements considered to be possibly essential include aluminium, germanium, lead, rubidium, and tin.||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 which 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. In terrestrial ecosystems, fungi play similar roles as bacteria: they mobilize nutritional elements composing matter that is inaccessible for other organisms and transport acquired nutrients to nutritionally scarce patches of ecosystem.
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