Nothing To Spit At 

The chemicals called nitrates have always been viewed as a toxic threat to humans. Nitrate compounds called nitrosamines—formed during the digestion of some meats—are suspected of causing stomach cancer, and nitrates in well water have been linked to rare cases of oxygen-starved blue babies. New research, however, indicates that moderate amounts of nitrates are not only safe, but may protect humans and animals against potentially fatal infections from microbes such as salmonella, shigella and E. coli.  

People normally ingest considerable amounts of nitrates in their diets, especially if they are vegetarians. Eighty to ninety percent of dietary nitrates come from vegetables, particularly green, leafy ones. Yet, vegetarians typically have lower cancer rates than people consuming fewer nitrates in their diets, which argues against nitrates being a cause of stomach cancer. 

Created by nitrate-producing bacteria living in the mouth, nitrates are also a natural component of human saliva. Experiments with rats have found that bacteria living in the backs of their mouths convert nitrates into nitrites. These nitrites, when swallowed, combine with stomach acid to form powerful antibiotics that kill pathogens that might otherwise infiltrate the intestines. 

One might think that stomach acid would be powerful enough to destroy bacteria without any help from nitrates, but that's not the case. When food enters the stomach, acidity decreases for up to two hours, and many bacteria survive to continue their journey into the intestines where they cause illness. 

Nitrate-producing bacteria are also thought to play a role in destroying the bacteria that initiate tooth decay, and may protect against Helicobacter pylori, the bacterium linked to ulcers and stomach cancer. The rural Yi, Bai, and Tai people living in China experience almost no tooth decay or stomach cancer. They consume a high-nitrate diet consisting almost entirely of vegetables, many cured in nitrate, along with small amounts of preserved meat. 

When a mother kisses a child's scrape, she may be doing more than addressing emotional needs. Studies suggest that the anti-bacterial nitrates in saliva may be helpful in healing if applied to a wound. 

[Editor: Data from the people in China who eat high-nitrate diets certainly calls into question the prevalent notion that pickled foods necessarily predispose to stomach cancer.]   Based on information in: Discover, Oct 1997