Q. I grew up in an Asian household and love to eat fermented vegetables like kimchi. But I'm confused about whether these foods are good for me or may pose a risk for stomach cancer because of the fermentation. Are there any studies on this? —Lydia Kang, Omaha
A. Stomach cancer rates are high in parts of Asia, especially Korea, and studies do indeed suggest that at least part of the reason may be all the kimchi, miso, and pickled fish people eat in that part of the world. Those foods contain N-nitroso compounds, which are likely carcinogens.
But that doesn't mean you need to banish them from your table. There are many risk factors for gastric cancer: Genetics, infection with the ulcer-related bacteria Helicobacter pylori, and lifestyle all play a part. If a close relative has had stomach cancer, for example, your risk is apt to be higher than average, which means you should be vigilant about getting checked. And you can be screened and treated for H. pylori infection.
If you eat a diet generally rich in fruits and vegetables of the unpickled variety, you'll lower your risk of stomach cancer. Regular exercise and maintaining a healthy weight will also help.
Otherwise, I recommend recalling the adage from the father of toxicology, Paracelsus: The dose makes the poison. All of us eat carcinogens on a fairly regular basis; our risk is defined by the ratio of beneficial to harmful exposures. Kimchi, miso, and other fermented foods are probably safe as a treat—say, once a week—in the context of a healthy lifestyle.