Nickel may be an essential trace mineral but its role in the body is unknown. The average adult body contains about 10 mg of nickel and it is found in many body tissues.
High concentrations of nickel are found in genetic material and it may be involved in protein structure and function. It may also play a role in hormone function, and may activate certain enzymes related to the breakdown or utilization of glucose.
Absorption and metabolism
N ickel is poorly absorbed from the gut and is carried in the body attached to a carrier protein. Most nickel is eliminated in the feces, some in urine and some in sweat.
Nickel deficiency in animals leads to decreased growth, dermatitis, pigment changes, liver damage and reproductive abnormalities. No deficiency symptoms have been reported in humans. Low blood levels of nickel may be found in those with liver and kidney disease.
Vegetables usually contain more nickel than other foods. High levels have been found in legumes, spinach, lettuce and nuts. Certain products, such as baking powder and cocoa powder, have been found to contain excessive amounts of nickel, perhaps because of nickel leaching from machinery during the manufacturing process. Soft drinking water and acid beverages may dissolve nickel from pipes and containers.
Recommended dietary intakes
Studies indicate a highly variable dietary intake of nickel, but most averages are about 0.2-0.7 mg per day.
Toxic effects of excess intake
Inhaled nickel is toxic and can cause nausea, vomiting and increase the risk of lung cancer. High levels of nickel in the diet may be associated with an increased risk of thyroid problems, cancer and heart disease.
Nickel in jewelry, dental materials, prosthetic joints or heart valves may cause allergic reactions such as contact dermatitis and eczema. Low nickel diets may bring improvement in some patients who are sensitive to nickel.