Urinary excretion of N-nitrosoproline in relation to consumption of raw and cooked vegetables in a Danish rural population.
Several recent case-control studies of gastric cancer have demonstrated the protective effect of consumption of vegetables. According to Correa's model of gastric carcinogenesis, the initiating agent is N-nitroso compounds either ingested or formed in vivo. In our study of endogenous nitrosation, we measured intragastric formation of N-nitroso compounds in 285 individuals by the nitrosation of proline; in this presentation we analysed the effect of consumption of vegetables on urinary excretion of N-nitrosoproline (NPRO). When adjustment was made for the dominating determinants of NPRO excretion (total nitrate intake and tobacco smoking), a marked difference in the effects of consumption of raw and cooled vegetables was seen: consumption of cooked vegetables increased endogenous nitrosation of proline, while consumption of raw vegetables had only a marginal effect. We suggest that the difference between raw and cooked vegetables is due to destruction of ascorbate in the cooking of the vegetables. The lack of a protective effect of consumption of raw vegetables on the rate on endogenous nitrosation of proline indicates, however, that the determinants of nitrosation of proline and the determinants of gastric cancer risk may be different.
Møller
H
H
Danish Cancer Registry, Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen.
Landt
J
J
Pedersen
E
E
Jensen
P
P
Autrup
H
H
Jensen
O M
OM
D003296:Cooking; D003718:Denmark; D004032:Diet; D006801:Humans; D009602:Nitrosamines / Q000652:urine*; D011159:Population Surveillance; D013274:Stomach Neoplasms / Q000209:etiology*; D014675:Vegetables
D009602:Nitrosamines; C010259:nitrosoproline