[Effect of nitrites and nitrates on various aspects of vitamin nutritional status].

Nitrites--and sometimes nitrates--decrease the biological availability of dietary vitamins in several animal species. 1. Numerous studies show that ingested nitrites decrease the stock of liver vitamin A in nonruminants (Rat, Pig, Chicken); the effect of nitrates is less pronounced even lacking. In vitro, experiments allow to think that vitamin A and beta-carotene can be destroyed by nitrites in the diet and/or in the gastrointestinal tract. 2. Some recent works--those of Lhuissier particularly--show that nitrites can affect some vitamins of B group and their metabolism. Thiamine and vitamin B6 contents of several tissues decrease when nitrites are fed to the Rat. In the case of thiamine, the result could be partially explained by destruction of the vitamin in the diet and may be in the gastrointestinal tract. No such explanation seems to be possible in the case of vitamin B6.