Nickel is an essential element in animals. It has been speculated that nickel may play a role in the maintenance of membrane structure, control of prolactin, nucleic acid metabolism or as a cofactor in enzymes. It appears that most dietary intakes would provide sufficient amounts of this element.

The importance of nickel for life was first discovered in the late sixties of 1900. Until then the nickel was observed only in terms of its toxicity to the body. The nickel was seen as "possible" essential trace element for humans, but its role in the body is mainly unknown. The highest number of researches related to the role of nickel in the body is made on chickens and rats. It is believed that the human body has about 10 mg of nickel.

Physiological role of nickel

The biological role of nickel is not yet fully known. Although nickel is generally evenly distributed in the body slightly larger amount is within the nucleic acid, especially in ribonucleic acid (RNA) and it is considered to affect the structure or function of the proteins associated with nucleic acids.

In addition, the role of nickel is associated with enzymes that affect the breakdown and use of glucose, but also in the creation of prolactin (and thus the production of milk in the mammary glands).

Enzymes that use nickel are not identified yet although nickel activates and inhibits enzymes that contain other metals. In addition to its role in enzymes, nickel is involved in the production and action of certain hormones.

Nickel affects optimal growth, healthy skin, bone structure. It is involved in iron metabolism (since it affects the absorption of iron from food) and plays a role in the creation of red blood cells. It is necessary in the metabolism of sugars, fats, hormones and cell membranes.

The majority of studies on the role of nickel in the body are done on animals, so their relevance to humans cannot be verified yet.

Metabolism

Nickel is poorly absorbed by the body. Less than 10% is absorbed in the gastrointestinal tract. The seven known nickel enzymes are urease, hydrogenase, CO-dehydrogenase, methyl-coenzyme M reductase, Ni-superoxide dismutase, glyoxalase I and cis-trans isomerase. When nickel enters the body it is distributed to all organs, but mostly in the kidney, bone, and the thyroid gland where it can exerts its toxicity. If nickel enters the body with nickel-contaminated air it is retained in the lungs. Nickel, which enters the blood stream is excreted in the urine, and if it is entered by the food it is excreted in the feces.

Food sources of nickel

Plants are the main source of nickel. Plants growing in soil contaminated with nickel can contain large amounts of nickel. The richest nickel foods are nuts, peas, beans, chocolate, soy, lentils, oats, buckwheat, barley, corn. Fruits that contain nickel are in bananas and pears. Food of animal origin is a poor with nickel, but nickel can be also found in drinking water. In addition to nickel in food, non-food sources of nickel are coins, jewelry, glasses frame, various household appliances, etc. A certain amount of nickel enters the body through the skin.

Recommended daily allowance

FDA - Food and Drug Administration 1984; NS - national survey 1986;

Nickel deficiency

The nickel deficiency in the body is rare due to its small needed quantity. However, it can occur with excessive sweating.

In humans, the lack of nickel has not been sufficiently tested, but symptoms in animals include slowed growth, reproductive changes and altered lipids (fats) and glucose levels in the blood.

In humans, it has been observed changes in skin colour, hair becomes coarser, hormonal imbalance and abnormal bone growth. Liver function is impaired and it affects the metabolism of iron, with less absorbed of iron.

Nickel deficiency also affect calcium and vitamin B₁₂ metabolism.

Overdose

Excess of nickel by diet is very rare. The most common symptoms are observed when a person comes into physical contact with nickel or inhalation with nickel-contaminated air (in industrial zones, cigarette smoke, car exhaust). In nickel sensitive people the dermatitis occurs that feels like an itch. It is believed that 10-20% of people are sensitive to nickel (contact sensitivity).

In larger amounts nickel is a carcinogen, as it increases the risk of lung, nose and throat cancer. In addition, there are also respiratory problems (breathing difficulties) when the nickel is inhaled. These problems include asthma and bronchitis.

Other problems that occur due to excess of nickel are: poor bone development, decreased resistance to infection, shortness of breath, headache, nausea, vomiting.

Nickel in medicine

The studies show that nickel level is increased in patients with heart attacks, burns and the after stronger shocks. Reducing the amount of nickel was observed in psoriasis, liver cirrhosis, kidney disease but it has not been shown that nickel helps in the treatment of these diseases.

References

Anke M., 1986, “Arsenic. In: Mertz W, ed. Trace Elements in Human and Animal Nutrition, Vol. 2, 5^th ed.,” Orlando, FL: Academic Press. Pp. 347–372.

Institute of Medicine (US) Panel on Micronutrients, 2001, “Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc,” Washington (DC): National Academies Press (US); 13. Arsenic, Boron, Nickel, Silicon, and Vanadium. [Web Reference]

Soetan K.O., Olaiya C. O. and Oyewole O.E., 2010, “The importance of mineral elements for humans, domestic animals and plants-A review,” African Journal of Food Science; 4(5): 200-222. [Web Reference]

Uthus E. and Poellot R., 1991, “Effect of dietary pyridoxine on arsenic deprivation in rats,” Magnesium and Trace Elements; 10: 339-339. [Web Reference]

Uthus E.O. and Seaborn C.D., 1996, “Deliberations and evaluations of the approaches, endpoints and paradigms for dietary recommendations of the other trace elements,” The Journal of Nutrition; 126(9): 2452S. [Web Reference]

Uthus E.O., 1994, “Diethyl maleate, an in vivo chemical depletor of glutathione, affects the response of male and female rats to arsenic deprivation,” Biological Trace Element Research; 46(3):247-259. [Web Reference]