Nitrate is important for the growth of plants as a key functional component of the nitrogen cycle. Nitrate accumulates in plants and at higher levels tends to be found in leaves, with crops such as lettuce and spinach having the highest nitrate levels. Human exposure to nitrate is mainly through the consumption of vegetables, as well as through water and other foods. Nitrate is relatively non-toxic, but its metabolites and reaction products-nitrite, nitric oxide and N-nitroso compounds-may have possible adverse health effects such as carcinogenesis. But some research also indicates that nitrite metabolites, such as nitric oxide, may have important physiological roles such as vasoregu-lation. Despite being a major source of nitrate in human diets, vegetable consumption is regarded as mainly beneficial to human health.
展开▼
