Chromium has an abundance of 0.033% in the Earth’s crust. It is a transition element that can occur in a number of valence states, with 0, +2, +3, and +6 being the most common. Trivalent chromium is the most stable form in biological systems. The principal ore is chromite. Chromium is used to harden steel, to manufacture stainless steel, and to form many useful alloys. It finds wide use as a catalyst. Hexavalent chro-mium is a strong oxidizing agent that comes primarily from industrial sources.
Trivalent chromium, the form of chromium found in foods and nutrient supplements, is one of the least toxic nutrients. The chromium often found in paints, welding fumes, and other industrial settings is hexava-lent and is several times more toxic than the trivalent form. Because trivalent chromium is poorly absorbed, high oral intakes would be necessary to attain toxic levels. In 2001, the US Food and Nutrition Board concluded that there are insufficient data to establish a tolerable UL for trivalent chromium. However, because of the current widespread use of chromium supplements, more research is needed to assess the safety of high-dose chromium intake from supplements.
There is no accurate method for reliable detection of marginal chromium deficiency. Chromium concen-trations in hair, urine, blood, and tissues can be used to assess recent chromium exposure, but are not long-term measures of chromium status. The only reliable indicator of chromium status is to monitor blood levels of glucose, insulin, lipid, and/or related vari-ables before and after chromium supplementation. A response in blood glucose can often be seen in 2 weeks or less, whereas effects on blood lipids may take longer.
The dietary chromium content of foods varies widely. The richest dietary sources of chromium are spices such as black pepper, brewer’s yeast, mushrooms, prunes, raisins, nuts, asparagus, beer, and wine. Refining of cereals and sugar removes most of the native chromium, but stainless-steel vessels in contact with acidic foods may contribute additional chromium.
There is currently no RDA set for dietary chro-mium, instead there are AI values [which were estab-lished by the US Food and Nutrition Board in 2001]: infants 0.2 μg (first 6 months), 5.5 μg (7–12 months), children 11 and 15 μg (1–3 and 4–8 years, respec-tively), teenage boys 25 and 35 μg (9–13 and 14–18 years, respectively), adult men 35 and 30 μg (19–50 years and 50 years and older, respectively), teenage girls 21 and 24 μg (9–13 and 14–18 years, respec-tively), adult women 25 and 20 μg (19–50 years and 51 years and older, respectively), pregnant women 29 and 30 μg (less than 18 years and 19–50 years, respec-tively), and lactating women 44 and 45 μg (less than 18 and 19–50 years, respectively). An AI was set based on representative dietary intake data from healthy individuals from the Third Nutrition and Health Examination Survey (NHANES III).