Nickel is a mineral element with the atomic number of 28. Nickel interacts with cobalt, vitamin C, vitamin E, vitamin B12 and vitamin B15. Nickel (Ni) and Cobalt (Co) are associated trace elements and considered essential to human health. While a cobalt and vitamin B12 relationship is well documented, a similar, but less documented affiliation applies to nickel and vitamin C.  Also less documented is the control nickel and cobalt exert over the muscular walls of the body's arteries. Nickel specifically affects the left coronary artery, resulting in vasodilation with low levels, and vasoconstriction with high levels, while cobalt exerts the same vasodilatation / vasoconstriction effect on the right coronary artery.

Nickel and vitamin C share a common antagonist; vitamin E. The association of nickel to vitamin C is similar to the one of cobalt to vitamin B12 as far as excess and deficiency symptoms and their interaction with other nutrients is concerned.  For instance, iron deficiency (anaemia) is often found in the presence of low nickel, and it is a well-known fact that vitamin C assists in iron absorption. Both vitamin C and nickel can also be beneficial for cirrhosis of the liver, hypoadrenalism and can improve insulin production in diabetics.

The cell receptors of nickel and cobalt are neurologically linked to the spinal segment T4, whereby both, its alignment, and various nutritional factors control the ratio of nickel and cobalt.  Alignment problems of T4, or nutritional imbalances involving nickel, cobalt, vitamin C, vitamin E, vitamin B12 and vitamin B15 can either result in localised physical discomfort, or they can trigger cardiac, cerebral, emotional and/or anxiety-problems due to blood flow changes to the heart or brain through their respective vasoconstrictive or vasodilating changes.

Intestinal absorption of nickel is less than 10%, with the kidneys controlling the retention or elimination of nickel, however most of it is eliminated in faeces, some in urine, and a small amount through sweat.

Nickel toxicity is usually not a problem unless several grams are ingested from non-dietary sources or there is a natural tendency to retain too much nickel, which could lead to asthma, angina an/or other cardiac symptoms as a result of nickel interfering with vitamin E activity.

Nickel is quite toxic in its gaseous form of nickel carbonyl, and it has the potential to cause cancer of the sinuses, throat and lungs when insoluble nickel compounds are inhaled for long periods of time. This does not apply to soluble nickel compounds such as chloride, nitrate, or sulphate. Once someone is sensitised to nickel from an allergic reaction to nickel-containing materials, subsequent contact will have to be avoided as it will continue to produce these effects. Skin reactions such as itching, burning, redness or other rashes are the most common symptoms with nickel sensitivity, however asthma attacks are another, but less frequent possibility in some people.

Nickel is a trace element that has been linked to skin allergies or dermatitis. Nickel is found in coins, costume jewellery, dental materials,  eyeglass frames, hair clips, pins, scissors and some kitchen appliances. Regular contact with these nickel products may allow some absorption into the body. Allergic dermatitis from nickel products is not at all uncommon, however of the approximately 10 mg in the body, significant amounts of nickel are found in RNA and DNA where it interacts with these nucleic acids.

Most of plasma nickel is a constituent of the circulating proteins nickeloplasmin and albumin, and it is also thought to be a factor in hormone, lipid and cell membrane metabolism. Insulin response is increased after ingesting nickel, which may be related to its activation of enzymes associated with the breakdown or utilization of glucose.