Introduction

Although chromium is recognized as a nutritionally essential mineral, scientists are not yet certain exactly how it functions in the body. The two most common forms of chromium are trivalent chromium (III) and hexavalent chromium (VI). Chromium (III) is the principal form in foods, as well as the form utilized by the body. The precise structure of the biologically active form of chromium is not known.

Food Sources

The amount of chromium in foods is variable, mainly due to variations in soil mineral content, and has been measured accurately in relatively few foods. Presently, there is no large database for the chromium content of foods. Processed meats, whole grain products, ready-to-eat bran cereals, green beans, broccoli, and spices are relatively rich in chromium. Foods high in simple sugars, such as sucrose and fructose, are not only low in chromium but have been found to promote chromium loss. Chromium content in different batches of the same food has been found to vary significantly.

Some important food sources of chromium:

Yeast	Meat	Green beans	Nuts	Red beans
Apple	Peanuts	Broccoli	Bananas	Orange juice

Recommended Dietary Allowance (RDA)

The European Union nor the USA have set a RDA for the general population. The accepted adequate intake for chromium should be between 30-50 µg/day for adults.

Inhibitors/stimulators:

The following food components have been found to stimulate the absorption of chromium:

Vitamin C – Chromium uptake is enhanced in animals when given at the same time as vitamin C.

The following food components have been found to inhibit the absorption of chromium:

Carbohydrates – Diets high in simple sugars (e.g., sucrose) compared to diets high in complex carbohydrates (e.g., whole grains) increase urinary chromium excretion in adults.

Iron – Chromium competes for one of the binding sites of the iron transport protein, transferrin, but many studies are inconclusive. Iron overload in hereditary hemochromatosis may interfere with chromium transport by competing for transferrin binding.

Functions in the Body

A biologically active form of chromium participates in glucose metabolism by enhancing the effects of insulin. Through its interaction with insulin receptors, insulin provides cells with glucose for energy and prevents blood glucose levels from becoming elevated. In addition to its effects on carbohydrate (glucose) metabolism, insulin also influences the metabolism of fat and protein.

Deficiency

Chromium deficiency was reported in three patients on long-term intravenous feeding who did not receive supplemental chromium in their intravenous solutions. These patients developed evidence of abnormal glucose utilization and increased insulin requirements that responded to chromium supplementation. Additionally, impaired glucose tolerance in malnourished infants responded to an oral dose of chromium chloride.

Several studies of male runners indicated that urinary chromium loss was increased by endurance exercise, suggesting that chromium needs may be greater in individuals who exercise regularly. In a more recent study, resistive exercise (weight lifting) was found to increase urinary excretion of chromium in older men. However, chromium absorption was also increased, leading to little or no net loss of chromium as a result of resistive exercise.

At present, research on the effects of inadequate chromium intake and risk factors for chromium insufficiency are limited by the lack of sensitive and accurate tests for determining chromium nutritional status.

Toxicity

Hexavalent chromium or chromium (VI) is a recognized carcinogen. Exposure to chromium (VI) in dust is associated with increased incidence of lung cancer and is known to cause inflammation of the skin (dermatitis). In contrast, there is little evidence that trivalent chromium or chromium (III) is toxic to humans.No adverse effects have been convincingly associated with excess intake of chromium (III) from food or supplements.

Most of the concerns regarding the long-term safety of chromium (III) supplementation arise from several studies in cell culture, suggesting chromium (III) may increase DNA damage. Presently, there is no evidence that chromium (III) increases DNA damage in living organisms.

Regulation

Once in the bloodstream, chromium is distributed to all parts of the body. Chromium will then pass through the kidneys and be eliminated in the urine in a few days. Most people normally eat or drink a small amount of chromium daily. Most of the chromium that one swallows leaves the body within a few days through the faeces and never enters the blood. A small amount (about 0.4–2.1%) will pass through the lining of the intestines and enter the bloodstream. Chromium(III) present in food can attach to other compounds that make it easier for chromium to enter the bloodstream from the stomach and intestines. This form of chromium is used by the body to carry out essential body functions. If skin comes into contact with chromium, very little will enter the body unless the skin is damaged.