Micronutrients are
nutrientA nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s required by humans and other living things throughout life in small quantities to orchestrate a whole range of physiological functions, but which the organism itself cannot produce. For people, they include dietary trace minerals in amounts generally less than 100 milligrams/day - as opposed to macrominerals which are required in larger quantities. The microminerals or trace elements include at least
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
,
cobaltCobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
,
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
,
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
,
iodineIodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
,
manganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
,
seleniumSelenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
,
zincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
and
molybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
. Micronutrients also include
vitaminA vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s, which are
organic compoundAn organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s required as nutrients in tiny amounts by an organism.
Public health initiatives for humans
At the 1990
World Summit for ChildrenThe United Nations World Summit for Children was held in New York on 29-30 September 1990, bringing together the then-largest-ever gathering of heads of state and government to commit to a set of goals to improve the well-being of children worldwide by the year 2000. The summit was the brain-child...
, the gathered nations identified deficiencies in three micronutrients – iodine, iron and
vitamin AVitamin A deficiency is a lack of vitamin A in humans. It is common in developing countries but rarely seen in developed countries. Night blindness is one of the first signs of vitamin A deficiency. Xerophthalmia and complete blindness can also occur since Vitamin A has a major role in...
- as being particularly common and posing public health risks in developing countries. The Summit set goals for elimination of these deficiencies. The Ottawa-based
Micronutrient InitiativeThe Micronutrient Initiative is an international not for profit agency based in Canada that works to eliminate vitamin and mineral deficiencies in developing countries...
was formed in response to this challenge with the mission to undertake research and fund and implement micronutrient programming.
As programming around these micronutrients grew, new research in the 1990s led to the implementation of
folateFolic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
and zinc supplementation programmes as well.
Priority programs include supplementation with vitamin A for children 6–59 months, zinc supplementation as a treatment for diarrhoeal disease, iron and folate supplementation for women of child-bearing age, salt iodization,
staple foodA staple food is one that is eaten regularly and in such quantities that it constitutes a dominant portion of a diet, and that supplies a high proportion of energy and nutrient needs. Most people live on a diet based on one or more staples...
fortification, multiple micronutrient powders, biofortification of crops and behaviour-centred nutrition education.
Salt iodization
Salt iodization is the recommended strategy for ensuring adequate human iodine intake. To iodize salt,
potassium iodatePotassium iodate is a chemical compound. It is ionic, made up of K+ ions and IO3- ions in a 1:1 ratio.-Chemical properties:Potassium iodate is an oxidizing agent and as such it can cause fires if in contact with combustible materials or reducing agents...
is added to salt after it is refined and dried and before it is packed. Although large-scale iodization is most efficient, given the proliferation of small scale salt producers in developing countries, technology for small-scale iodization has also been developed. International organizations work with national governments to identify and support small salt producers in adopting iodization activity.
In 1990, less than 20 per cent of households in developing countries were consuming iodized salt. By 1994, international partnerships had formed in a global campaign for Universal Salt Iodization. By 2008, it was estimated that 72 per cent of households in developing countries were consuming iodized salt and the number of countries in which iodine deficiency disorders were a public health concern reduced by more than half from 110 to 47 countries.
The Network for Sustained Elimination of Iodine Deficiency (The Iodine Network) is an international network of UN, not-for-profit, scientific and industry organizations, with the mission to promote and support collaboration in efforts to ensure adequate iodine consumption, primarily through the achievement of universal salt iodization (USI).
Vitamin A supplementation
In 1997, national vitamin A supplementation programming received a boost when experts met to discuss rapid scale-up of supplementation activity and the Micronutrient Initiative, with support from the Government of Canada, began to ensure vitamin A supply to UNICEF.
In areas with vitamin A deficiency, it is recommended that children aged 6–59 months receive two doses annually. In many countries, vitamin A supplementation is combined with immunization and campaign- style health events.
Global vitamin A supplementation efforts have targeted 103 priority countries. In 1999, 16 per cent of children in these countries received two annual doses of vitamin A. By 2007, the rate increased to 62 per cent.
The Micronutrient Initiative, with funding from the Government of Canada, supplies 75 per cent of the vitamin A required for supplementation in developing countries.
Double-fortified salt
Double-fortified salt (DFS) is a public health tool for delivering nutritional iron. DFS is fortified with both iodine and iron. It was developed by Venkatesh Mannar, Executive Director of the
Micronutrient InitiativeThe Micronutrient Initiative is an international not for profit agency based in Canada that works to eliminate vitamin and mineral deficiencies in developing countries...
and
University of TorontoThe University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...
Professor Levente Diosady, who discovered a process for coating iron particles with a vegetable fat to prevent the negative interaction of iodine and iron.
It was first used in public programming in 2004. As of September 2010 DFS was being produced only in the Indian State of
Tamil NaduTamil Nadu is one of the 28 states of India. Its capital and largest city is Chennai. Tamil Nadu lies in the southernmost part of the Indian Peninsula and is bordered by the union territory of Pondicherry, and the states of Kerala, Karnataka, and Andhra Pradesh...
and distributed through a state school feeding program. In September 2010, Venkatesh Mannar was named a Laureat of the California-based Tech Awards for his work in developing Double-Fortified Salt.
Micro-enriched fertilization
The returns of applying micronutrient-enriched fertilizers could be huge for human health, social and economic development. Research has shown that enriching fertilizers with micronutrients had not only an impact on plant deficiencies but also on humans and animals, through the food chain. A 1994 report by the World Bank estimated that micronutrient malnutrition costs developing economies at least 5 percent of gross domestic product. The Asian Development Bank has summarized the benefits of eliminating micronutrient deficiencies as follows:
Along with a growing understanding of the extent and impact of micronutrient malnutrition, several interventions have demonstrated the feasibility and benefits of correction and prevention. Distributing inexpensive capsules, diversifying to include more micronutrient-rich foods, or fortifying commonly consumed foods can make an enormous difference. Correcting iodine, vitamin A, and iron deficiencies can improve the population-wide intelligence quotient by 10-15 points, reduce maternal deaths by one fourth, decrease infant and child mortality by 40 percent, and increase people’s work capacity by almost half. The elimination of these deficiencies will reduce health care and education costs, improve work capacity and productivity, and accelerate equitable economic
growth and national development. Improved nutrition is essential to sustained economic growth.5 Micronutrient deficiency elimination is as cost effective as the best public health interventions and fortification is the most cost-effective strategy.
Addressing zinc deficiencies through zinc fertilization
Experiments show that soil and foliar application of zinc fertilizer can effectively reduce the phytate zinc ratio in grain. People who eat bread prepared from zinc enriched wheat show a significant increase in serum zinc, suggesting that the zinc fertilizer strategy is a promising approach to address
zinc deficienciesZinc deficiency is insufficient zinc to meet the needs of biological organisms. It can occur in both plants and animals. Zinc deficient soil is soil in which there is insufficient zinc to allow plants to grow normally.-Description:...
in humans.
Where zinc deficiency is a limiting factor, zinc fertilization can increase crop yields. Balanced crop nutrition supplying all essential nutrients, including zinc, is a cost effective management strategy. Even with zinc-efficient varieties, zinc fertilizers are needed when the available zinc in the topsoil becomes depleted.
Micronutrients for plants
There are about seven nutrients essential to plant growth and health that are only needed
in very small quantities. These are
manganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
,
boronBoron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
,
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
,
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
,
chlorineChlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
,
molybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
, and
zincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
. Some consider
sulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
a micronutrient, but it is listed here as a macronutrient. Though these are present in only small quantities, they are all necessary.
Boron is believed to be involved in carbohydrate transport in plants; it also assists in metabolic regulation. Boron deficiency will often result in bud dieback.
Chlorine is necessary for
osmosisOsmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides...
and ionic balance; it also plays a role in
photosynthesisPhotosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
.
Copper is a component of some enzymes and of vitamin A. Symptoms of copper deficiency include browning of leaf tips and chlorosis.
Iron is essential for chlorophyll synthesis, which is why an iron deficiency results in chlorosis.
Manganese activates some important enzymes involved in
chlorophyllChlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
formation. Manganese deficient plants will develop chlorosis between the veins of its leaves. The availability of manganese is partially dependent on soil pH.
Molybdenum is essential to plant health. Molybdenum is used by plants to reduce nitrates into usable forms. Some plants use it for nitrogen fixation, thus it may need to be added to some soils before seeding legumes.
Zinc participates in chlorophyll formation, and also activates many enzymes. Symptoms of zinc deficiency include chlorosis and stunted growth.
Micronutrient deficiencies in crops
Micronutrient deficiencies are widespread. 50% of world cereal soils are deficient in zinc and 30% of cultivated soils globally are deficient in iron. Steady growth of crop yields during recent decades (in particular through the
Green RevolutionGreen Revolution refers to a series of research, development, and technology transfer initiatives, occurring between the 1940s and the late 1970s, that increased agriculture production around the world, beginning most markedly in the late 1960s....
) compounded the problem by progressively depleting soil micronutrient pools.
In general, farmers only apply micronutrients when crops show deficiency symptoms, while micronutrient deficiencies decrease yields before symptoms appear. Some common farming practices (such as liming acid soils) contribute to widespread occurrence of micronutrient deficiencies in crops by decreasing the availability of the micronutrients present in the soil. Also, extensive use of
glyphosate is increasingly suspected to impair micronutrient uptake by crops, especially with regard to manganese, iron and zinc.
See also
- List of micronutrients
- Macronutrient (ecology)
- Dietary mineral
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
- Manganese deficiency (medicine)
Manganese deficiency in humans results in a number of medical problems. Manganese is a vital element of nutrition in very small quantities...
External links