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Do fermented foods cause cancer?

Does your plate of sauerkraut or pickles come with a side of cancer? Yes and no, so let me explain. Meanwhile, I'll munch on these pickles I just fermented, and you can too.

Salted foods such as pickled and fermented vegetables and fish are considered to increase the risk of stomach cancer—with some caveats. As with anything, the dose and context make the poison (not that these foods are poisonous).

Pickled and fermented foods

Pickled red onion and cucumbers

Studies on foods preserved by salting were all done in Asia, where salted foods are eaten in high amounts daily by many people, and one study in Europe. A significant increase of 9 percent higher stomach cancer risk (but not death from stomach cancer) was seen for every 20 grams of vegetables preserved heavily in salt and eaten daily (that's under an ounce).

The studies also showed a probable increase in stomach cancer rates for fish preserved Cantonese style, a specific way of preserving raw fish that is dried in the sun. This salted and drying method is part of a traditional way of eating for people in Southern China.

The rates of stomach cancer are certainly higher in Asia and Eastern Europe. The highest rates of stomach cancer in the world are found in Korea, followed by Mongolia and Japan. China has the 6th highest rate of stomach cancer in the world. So there may be other factors at work, or what researchers call confounding factors, which lead to an increased rate of cancer.

I'll return to the confounding factors, but it's important to note that North America and Africa have the lowest rates of stomach cancer in the world. We've come a long way from stomach cancer being the top cause of cancer death, as it was in the late 1930's. In the past decade, the number of new cases has declined by 2.5% every year in the U.S. Stomach cancer affects more people over 65 years old: Six out of every 10 people diagnosed are 65 or older. For most cancers, the highest risk factor is age, apart from smoking.


Sauerkraut is a fermented food

The confounding factors for which stomach cancer may be higher in certain countries include the fact that the studies did not adjust for the bacterium Helicobacter pylori. The H. pylori infection is one of main causes of stomach cancer (some studies did adjust for smoking, another leading cause). It is now treated effectively in the U.S. with antibiotics. Moreover, we have to take into account that perhaps these populations rely more on salted foods to preserve them, and eat less fresh food, due to a lack of refrigeration.

Other factors for higher rates of stomach cancer are: Exposure to occupational chemicals; genetic mutations (particularly in Asian populations); and an autoimmune type of anemia called pernicious anemia, and autoimmune gastritis.

Fermenting cabbage

A fermentation kit

Why would highly-salted and preserved foods cause stomach cancer? Surprisingly, it may not be directly related to salt intake, as previously thought. Fermented foods produce N-nitroso compounds that may interact with the H. pylori infection to cause cancer. Certain people may be more sensitive to small amounts of these compounds.

Because the high rates of cancer are limited to certain populations, global recommendations have not been made to avoid these foods. So there's no reason to avoid these healthful foods in the U.S. In fact, I encourage eating fermented foods such as pickles, sauerkraut, kimchi, tempeh, miso, and other fermented vegetables.

Fermented foods are not pickled foods, however. What sets them apart is heat and acid. Pickled foods are usually done in a short time using heat and vinegar. Pickled foods don’t have as many benefits as fermented foods. For the most benefit, always buy refrigerated pickles or sauerkraut made without vinegar. Fermented foods only use salt or other spices and are never heated. This means they have probiotic cultures which are beneficial for the body. If the food manufacturer lists the number of probiotics, that’s even better.

Cabbage and pickling spice
Prepping cabbage for sauerkraut

Raw cabbage and pickling spice (top); massaging cabbage for fermentation.

You can also reap the benefits of probiotics by eating cultured dairy or nondairy products, such as yogurt and kefir. People who eat more cultured milk products also have a lower risk of bladder cancer.

If you’re hesitant to try fermented vegetables, there are very good reasons to try them.

  • Eat more raw vegetables. Raw foods have a different nutrient profile than cooked and introduce diverse microbes for gut health. Fermenting also brings out probiotics, which strengthen and heal the gut.

  • Benefit from cancer preventative compounds. The cabbage in sauerkraut has eight different compounds to reduce cancer risk.

  • A specific compound called indoles in cabbage and other fibrous vegetables reduce and even inactivate excess estrogen, which drives breast cancer and other hormone-related cancers.

  • You can pump up the anti-cancer compounds along with the flavor by adding green tea, turmeric, garlic, onions, and other green and yellow vegetables to the brine.

I made sauerkraut for the first time and it was easier than I thought. I've moved on to making fermented pickles, and, as you can see, they have a satisfying crunch and are delightful in a sandwich. Most of all, I believe there is also something deeply satisfying about waiting for something to reach its peak flavor and nutrient value in today's too fast-paced world, much like gardening.


Fermenting pickles

Leave the stomach cancer fears aside, and try making your own fermented foods. For good ideas on fermenting foods and recipes, see fellow registered dietitian nutritionist Rosie Schwartz, author of the The Enlightened Eater's Whole Foods Guide, with "Top 6 fermented foods for your microbiota," and Chef Catherine Brown, and her recipe for beautiful Lacto-Fermented Spicy Carrots.

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