Content and bioavailability of trace elements in vegetarian diets.

This review compares the content and major food sources of copper, manganese, selenium, and zinc in vegetarian and omnivorous diets. Interactions affecting trace element bioavailability and their impact on the trace element status of vegetarians are discussed. Adult vegetarian diets often have a lower zinc and selenium content but a higher copper and manganese content compared with omnivorous diets. Cereals are the primary sources of copper, manganese, and selenium in most diets and the major source of zinc in many vegetarian diets; flesh floods are the primary source of zinc and secondary source of selenium in omnivorous diets. Despite the apparent lower bioavailability of zinc, copper, manganese, and selenium in vegetarian diets because of the high contents of phytic acid and/or dietary fiber and the low content of flesh foods in the diet, the trace element status of most adult vegetarians appears to be adequate. Children, however, appear to be more vulnerable to suboptimal zinc status, presumably because of their high zinc requirements for growth and their bodies' failure to adapt to a vegetarian diet by increased absorption of dietary zinc.