Chromium content of foods and diets.

Comparatively few valid data are available on the chromium content of foods and on the dietary chromium (Cr) intake of various populations. This is chiefly because of the difficulties encountered in contamination control during sampling, sample pretreatment, and analysis. Moreover, there are several analytical problems involved that are mostly owing to the low concentration level of Cr in foods. However, with the recent establishment of food reference materials with certified low concentrations of Cr, the analytical validity of studies on Cr content of foods and on its dietary intake by various populations can be ascertained. With the exception of herbs and condiments, and certain other special food items with a relatively low average consumption rate, such as tea, coffee, and some candies, most foods contain Cr below 100 micrograms/kg. Staple foods, particularly cereals and milk, are very low (less than or equal to 10 micrograms/kg) in Cr, showing little or no geographic variation. Food processing may increase food Cr content depending on the process. Processes, such as meat grinding and homogenization using stainless-steel equipment, very strongly increase the Cr content of foods. Also, acidic fruit juices in contact with steel cans are high in Cr, whereas cooking in aluminium vessels reduces the Cr content of foods. Average dietary Cr intake seems to fluctuate considerably among countries. In many developing countries, such as Brazil, the Sudan, and Iran, the dietary intake is high, from 50-100 micrograms/d, whereas in certain developed countries, such as Finland, Sweden, Switzerland, and the US, the intake is 50 micrograms/d or lower and, consequently, at or below the estimated safe and adequate daily dietary intake range of 50-200 micrograms/d established by the US National Academy of Sciences. The average Cr content of human milk is below 0.5 micrograms/L, thus resulting in a very low average intake of 0.3 microgram Cr/d by exclusively breast-fed infants in the US and Finland.