When Dr. Lisa Ganjhu thinks about kimchi, sauerkraut, and yogurt, she thinks about something her grandparents knew long before scientists had the tools to study it: fermented foods are good for you. "We've been doing this for ages and we just found out more recently that it's actually helped our gut health," said Dr. Ganjhu, a gastroenterologist with NYU Langone Health. Now, the federal government agrees. The latest U.S. dietary guidelines specifically encourage Americans to eat more fermented foods like kimchi, yogurt, and sauerkraut for better gut health.
Fermentation is an ancient method of food preservation that goes back thousands of years, to a time when humans had no refrigerators but needed to keep food from spoiling. Cultures around the world developed their own versions: kimchi in Korea, sauerkraut in Germany, yogurt across the Middle East and South Asia, idli and dosa in South India. The process uses naturally occurring bacteria and yeast to break down food and keep it from going bad.
Today, this ancient practice is getting fresh attention. More people are paying attention to their gut health, and scientists are finding that fermented foods may help in surprising ways. The bacteria in these foods don't just survive the journey through your digestive system — they actively work there, competing with less helpful bacteria already living in your intestines and helping keep the whole system in balance.
Dalia Perelman, a research dietitian at Stanford University, said scientists are still learning exactly why fermented foods help. "What is it that makes the fermented foods so healthy? The answer is we're still working on it," she said. But the evidence is strong enough that the government is now recommending them.
Not all fermented foods are equally healthy, though. Beer and wine go through fermentation, but they don't count as gut-friendly foods. "If anything, they influence our own microbiome in more of a negative way," Dr. Ganjhu said. And heavily processed foods that market themselves as probiotic — think probiotic sodas or chocolate — aren't the same as the real thing.
Experts recommend sticking with whole fermented foods: yogurt, kefir, kimchi, sauerkraut, tempeh, fermented beets, or fermented green beans. Barbara Olendzki, who directs the Center for Applied Nutrition at UMass Chan Medical School, said these foods are a simple addition that works for almost anyone. And when shopping, look for products that say "live cultures" on the label, not just "probiotic." "The best yogurt you can have is just plain, fermented milk with culture," Dr. Ganjhu said. "Let it do its business."