Increase in human exposure to methylamine precursors of N-nitrosamines after eating fish
Zeisel, S.H.; DaCosta, K.A.
Cancer Research 46(12 Pt 1): 6136-6138
1986
ISSN/ISBN: 0008-5472 PMID: 3779634 Document Number: 270495
Consumption of fish has been encouraged recently because it may prevent mortality due to heart disease. Fish contains methylamines, which are precursors of N-nitrosamines. Nitrosamines can act as potent carcinogens in a wide range of animal species and there is no reason to assume that man is resistant. Five subjects ingested a diet of known methylamine content for 2 days. On day 3, they ate fish at the luncheon and dinner meals. On day 4, they again ate the control diet. A single portion of fish had a methylamine content similar to that normally excreted by the subject in 2 days. Urinary excretion of monomethylamine remained constant (1.3 to 1.5 mu mol/24 h kg body weight) throughout the study. Dimethylamine excretion increased more than 4-fold after fish was eaten (from 5.6 to 24.1 mu mol/24 h kg body weight) and trimethylamine excretion increased more than 8-fold (from 0.2 to 1.6 mu mol/24 h kg body weight). It was concluded that consumption of fish significantly increased exposure to methylamines, particularly to dimethylamine. Although there is potential for the conversion in vivo of dimethylamine to nitrosodimethylamine, a carcinogen, no study is known to have ascertained that the ingestion of fish increases the risk of cancer. That should be carefully investigated before recommending change of eating habits.