They form part of the essential chemistry of soils and plants. Beets, radishes, spinach, and lettuce contain the highest levels of nitrates. Nitrites are less common in the food supply, but are produced in the mouth and intestine by bacterial action on protein and nitrates. Nitrites , usually as sodium salts, have been used widely as preservatives, especially in bacon and other processed meats. Saltpeter is the best known nitrite with its undeserved reputation as the sex-drive inhibitor.
Nitrites also occur naturally in foods.
The chief concern is the ability of nitrites to combine with amino acids in GIT to form nitrosamine s, potentially carcinogenic molecules. Vitamin C inhibits nitrosamine formation and is thought to protect against GIT cancer. Vitamin C is an antioxidant preservative, and can replace less desirable preservatives in some foods. Tobacco smoke is the major source of human exposure to nitrosamines. Salicylates Salicylates are common in vegetables and fruit.