The presence of an aldehyde dehydrogenase inhibitor in animal diets and its effects on the experimental results in alcohol studies.

1. The effects of chronic ethanol administration on the metabolism of ethanol and acetaldehyde were studied in rats fed on a commercial diet containing an aldehyde dehydrogenase inhibitor, calcium cyanamide (calcium carbimide), as a contaminant in the calcinated bone-meal fraction of the diet. 2. Rats given an ethanol solution (150 ml/l) for 3 months and fed on a diet containing calcinated bone meal showed two times higher activity of the low-Km acetaldehyde dehydrogenase in the liver, 26% higher rate of ethanol elimination, and two to three times lower acetaldehyde levels in blood during ethanol elimination compared with control rats pair-fed on the same diet. 3. The results obtained from the ethanol-treated rats were similar to those obtained in experiments on control rats fed on diets not containing calcinated bone meal. 4. Experiments performed in vitro and in vivo on the inhibition of the acetaldehyde metabolism by cyanamide suggested that the apparent effects of chronic ethanol intake were really caused by calcium cyanamide in the diet.