In the context of nutrition, a mineral is a chemical element. Some "minerals" are essential for life, but most are not.[1] Minerals are one of the four groups of essential nutrients; the others are vitamins, essential fatty acids, and essential amino acids.[2] The five major minerals in the human body are calcium, phosphorus, potassium, sodium, and magnesium.[3] The remaining elements are called "trace elements". The generally accepted trace elements are iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine, and selenium;[4] there is some evidence that there may be more.
Four elements comprise 96% of the human body by weight: carbon, hydrogen, oxygen, and nitrogen (CHON). These elements are usually not included in lists of nutrient minerals. They are sometimes referred to as macrominerals. The minor minerals (also called trace elements) compose the remainder and are usually the focus of discussions of minerals in the diet.
Plants obtain minerals from soil.[5] Animals ingest plants, thus moving minerals up the food chain. Larger organisms may also consume soil (geophagia) or use mineral resources such as salt licks to obtain minerals.
Finally, although mineral and elements are in many ways synonymous, minerals are only bioavailable to the extent that they can be absorbed. To be absorbed, minerals either must be soluble or readily extractable by the consuming organism. For example, molybdenum is an essential mineral, but metallic molybdenum has no nutritional benefit. Many molybdates are sources of molybdenum.
See main article: Composition of the human body. Nineteen chemical elements are known to be required to support human biochemical processes by serving structural and functional roles, and there is evidence for around ten more.[6]
Oxygen, hydrogen, carbon and nitrogen are the most abundant elements in the body by weight and make up about 96% of the weight of a human body. Calcium makes up 920 to 1200 grams of adult body weight, with 99% of it contained in bones and teeth. This is about 1.5% of body weight. Phosphorus occurs in amounts of about 2/3 of calcium, and makes up about 1% of a person's body weight.[7] 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. The remaining ≈18 ultratrace minerals comprise just 0.15% of the body, or about one hundred grams in total for the average person. Total fractions in this paragraph are amounts based on summing percentages from the article on chemical composition of the human body.
Some diversity of opinion exist about the essential nature of various ultratrace elements in humans (and other mammals), even based on the same data. For example, whether chromium is essential in humans is debated. No Cr-containing biochemical has been purified. The United States and Japan designate chromium as an essential nutrient,[8] [9] but the European Food Safety Authority (EFSA), representing the European Union, reviewed the question in 2014 and does not agree.[10]
Most of the known and suggested mineral nutrients are of relatively low atomic weight, and are reasonably common on land, or for sodium and iodine, in the ocean. They also tend to have soluble compounds at physiological pH ranges: elements without such soluble compounds tend to be either non-essential (Al) or, at best, may only be needed in traces (Si).
| Dietary element | RDA/AI Male/Female (US) [mg][11] | UL (US and EU) [mg] | Category | High nutrient density dietary sources | Terms for deficiency/excess | |
|---|---|---|---|---|---|---|
| Potassium | 4700 | A systemic electrolyte and is essential in coregulating ATP with sodium | Sweet potato, tomato, potato, beans, lentils, dairy products, seafood, banana, prune, carrot, orange[12] | hypokalemia / hyperkalemia | ||
| Chlorine | 2300 | 3600; | Needed for production of hydrochloric acid in the stomach, in cellular pump functions and required in host defense | Table salt (sodium chloride) is the main dietary source. | hypochloremia / hyperchloremia | |
| Sodium | 1500 | 2300; | 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 | 1000 | 2500; 2500 | Needed for muscle, heart and digestive system health, builds bone (see hydroxyapatite), supports synthesis and function of blood cells, helps in blood clotting | Dairy products, eggs, canned fish with bones (salmon, sardines), green leafy vegetables, nuts, seeds, tofu, thyme, oregano, dill, cinnamon.[13] | hypocalcaemia / hypercalcaemia | |
| Phosphorus | 700 | 4000; 4000 | A component of bones (see hydroxyapatite), cells, in energy processing, in DNA and ATP (as phosphate) and many other functions | Red meat, dairy foods, fish, poultry, bread, rice, oats.[14] [15] In biological contexts, usually seen as phosphate[16] | hypophosphatemia / hyperphosphatemia | |
| Magnesium | 420/320 | 350; 250 | Required for processing ATP and for bones | Spinach, legumes, nuts, seeds, whole grains, peanut butter, avocado[17] | hypomagnesemia (magnesium deficiency) / hypermagnesemia | |
| Iron | 8/18 | 45; | Required for many proteins and enzymes, notably hemoglobin to prevent anemia | Meat, seafood, nuts, beans, dark chocolate[18] | iron deficiency / iron overload disorder | |
| Zinc | 11/8 | 40; 25 | Required for several classes of enzymes such as matrix metalloproteinases, liver alcohol dehydrogenase, carbonic anhydrase and zinc finger proteins | Oysters*, red meat, poultry, nuts, whole grains, dairy products[19] | zinc deficiency / zinc toxicity | |
| Manganese | 2.3/1.8 | 11; | Required co-factor for superoxide dismutase | Grains, legumes, seeds, nuts, leafy vegetables, tea, coffee[20] | manganese deficiency / manganism | |
| Copper | 0.9 | 10; 5 | Required co-factor for cytochrome c oxidase | Liver, seafood, oysters, nuts, seeds; some: whole grains, legumes | copper deficiency / copper toxicity | |
| Iodine | 0.150 | 1.1; 0.6 | Required for the synthesis of thyroid hormones and to help enzymes in host defense | Seaweed (kelp or kombu)*, grains, eggs, iodized salt[21] | iodine deficiency (goiter) / iodism (hyperthyroidism[22]) | |
| Molybdenum | 0.045 | 2; 0.6 | Required for the functioning of xanthine oxidase, aldehyde oxidase, and sulfite oxidase[23] | Legumes, whole grains, nuts | molybdenum deficiency / molybdenum toxicity[24] | access-date=12 June 2014--> |
| Selenium | 0.055 | 0.4; 0.3 | Essential to activity of antioxidant enzymes like glutathione peroxidase | Brazil nuts, seafoods, organ meats, meats, grains, dairy products, eggs[25] | selenium deficiency / selenosis | |
| Cobalt | none | Cobalt is available for use by animals only after having been processed into complex molecules (e.g., vitamin B12) by bacteria. Humans contain only milligrams of cobalt in these cofactors. A deficiency of cobalt leads to pernicious anemia. | Animal muscle and liver are good dietary sources, also shellfish and crab meat.[26] | pernicious anemia / cobalt poisoning |
* One serving of seaweed exceeds the US UL of 1100 μg but not the 3000 μg UL set by Japan.[27]
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 (calcium carbonate, calcium citrate) or magnesium (magnesium oxide), or iron (ferrous sulfate, iron bis-glycinate).
The dietary focus on chemical elements derives from an interest in supporting the biochemical reactions of metabolism with the required elemental components.[28] 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 recommendations are not adequately met by the diet. An example would be a diet low in dairy products, and hence not meeting the recommendation for calcium.
The list of minerals required for plants is similar to that for animals. Both use very similar enzymes, although differences exist. For example, legumes host molybdenum-containing nitrogenase, but animals do not. Many animals rely on hemoglobin (Fe) for oxygen transport, but plants do not. Fertilizers are often tailored to address mineral deficiencies in particular soils. Examples include molybdenum deficiency, manganese deficiency, zinc deficiency, and so on.
The gap between recommended daily intake and what are considered safe upper limits (ULs) can be small. For example, for calcium the U.S. Food and Drug Administration set the recommended intake for adults over 70 years at 1,200 mg/day and the UL at 2,000 mg/day.[11] The European Union also sets recommended amounts and upper limits, which are not always in accord with the U.S. Likewise, Japan, which sets the UL for iodine at 3000 μg versus 1100 for the U.S. and 600 for the EU.[27] In the table above, magnesium appears to be an anomaly as the recommended intake for adult men is 420 mg/day (women 350 mg/day) while the UL is lower than the recommended, at 350 mg. The reason is that the UL is specific to consuming more than 350 mg of magnesium all at once, in the form of a dietary supplement, as this may cause diarrhea. Magnesium-rich foods do not cause this problem.[29]
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.[4] 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.[28] 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 are suspected to have a role in health, but with weaker evidence.[4] In particular, trace arsenic seems to have a positive effect on some organisms, but so does lead, showcasing the uncertainty behind whether some trace elements are truly essential. Strontium is tolerated and is a component of some drugs,[30] but it is not essential, only beneficial. Non-essential elements can sometimes appear in the body when they are chemically similar to essential elements (e.g. Rb+ and Cs+ replacing Na+), so that essentiality is not the same thing as uptake by a biological system.
| Element | Description | Excess | |
|---|---|---|---|
| Bromine | Possibly important to basement membrane architecture and tissue development, as a needed catalyst to make collagen IV.[31] | bromism | |
| Arsenic | Essential in rat, hamster, goat and chicken models, but no research has been done in humans.[32] | arsenic poisoning | |
| Nickel | Nickel is an essential component of several enzymes, including urease and hydrogenase.[33] Although not required by humans, some are thought to be required by gut bacteria, such as urease required by some varieties of Bifidobacterium.[34] In humans, nickel may be a cofactor or structural component of certain metalloenzymes involved in hydrolysis, redox reactions and gene expression. Nickel deficiency depressed growth in goats, pigs, and sheep, and diminished circulating thyroid hormone concentration in rats.[35] | Nickel toxicity | |
| Fluorine | Might have a role in biologic mineralisation, and fluoride deficiency symptoms have been found in goats, but there is no clear evidence of essentiality in humans. Research indicates that the primary dental benefit from fluoride occurs at the surface from topical exposure.[36] [37] However, even if not essential, fluorine would still be a beneficial element for this reason. Of the minerals in this table, fluoride is the only one for which the U.S. Institute of Medicine has established an Adequate Intake.[38] | Fluoride poisoning | |
| Boron | Boron is an essential plant nutrient, required primarily for maintaining the integrity of cell walls.[39] [40] [41] Boron has been shown to be essential to complete the life cycle in representatives of all kingdoms of life.[42] In animals, supplemental boron has been shown to reduce calcium excretion and activate vitamin D.[43] | No acute effects (LD50 of boric acid is 2.5 grams per kilogram body weight) | |
| Lithium | Based on plasma lithium concentrations, biological activity and epidemiological observations, there is evidence, not conclusive, that lithium is an essential nutrient.[44] [45] | Lithium toxicity | |
| Chromium | Proposed to be 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[46] [47] | chromium deficiency / chromium toxicity | |
| Silicon | Deficiency symptoms have been found in chickens and rats, though not humans. Circumstantial evidence suggests that it is an essential nutrient, probably having an effect on the function and composition of brain and bone. | ||
| Vanadium | Has an established, albeit specialized, biochemical role in other organisms (algae, lichens, fungi, bacteria), and there is significant circumstantial evidence for its essentiality in humans. It is rather toxic for a trace element and the requirement, if essential, is probably small. | ||
| Tin | Rats fed a tin-free diet exhibited improper growth, but the evidence for essentiality is otherwise limited. | Tin poisoning | |
| Other | Tungsten, the early lanthanides, and cadmium have specialized biochemical uses in certain lower organisms, but these elements appear not to be used by mammals.[48] |
Diverse ions are used by animals and microorganisms for the process of mineralizing structures, called biomineralization, used to construct bones, seashells, eggshells,[49] exoskeletons and mollusc shells.[50]
Minerals can be bioengineered by bacteria which act on metals to catalyze mineral dissolution and precipitation.[51] Mineral nutrients are recycled by bacteria distributed throughout soils, oceans, freshwater, groundwater, and glacier meltwater systems worldwide.[51] [52] Bacteria absorb dissolved organic matter containing minerals as they scavenge phytoplankton blooms.[52] Mineral nutrients cycle through this marine food chain, from bacteria and phytoplankton to flagellates and zooplankton, which are then eaten by other marine life.[51] [52] In terrestrial ecosystems, fungi have similar roles as bacteria, mobilizing minerals from matter inaccessible by other organisms, then transporting the acquired nutrients to local ecosystems.[53] [54]