Fermented foods "have phenomenal benefits in your overall Sauerkrautwellness," gushes Dr. Mercola. "7 must-eat fermented foods for a healthy gut," promises EatingWell online.
Humans have enjoyed fermented foods—from wine, beer, and vinegar to pickles, olives, yogurt, and cheese—for millennia. Before refrigeration, people used fermenting to preserve foods. But can fermented foods make you healthier? Here's a look at the evidence.
Fermentation starts when microbes—bacteria or yeast—gobble up carbs in fruits, vegetables, milk, or grains. Over time, the bacteria turn some of the carbs into acids (in foods like sauerkraut), or the yeast turns some of the carbs into alcohol and carbon dioxide (in beer, wine, and liquor). The acids and alcohol help fend off other microbes that would cause the food to spoil.
Does a fermented food still contain live microbes when you eat it? If it has been filtered, heated, or canned, they've probably been removed or inactivated.
But foods like refrigerated yogurt, kefir, kimchi, kombucha, and sauerkraut can contain as many as 1 million to 1 billion cells of live microbes in every gram.1 That's as many bugs as a typical American gets from a whole day's worth of food.2
Where’s the evidence?
“Yogurt and fermented dairy is where the lion’s share of the knowledge is on the benefits of fermented foods,” says Maria Marco, associate professor of food science and technology at the University of California, Davis. (Marco’s research has been partially funded by the dairy and olive industries, as well as the National Institutes of Health and others.)
For example, yogurt cultures deliver enzymes to your gut, where they break up the milk sugar (lactose) that some people can’t digest.3 And some studies find a lower risk of type 2 diabetes in yogurt eaters.4
But what excites many enthusiasts is the idea that each swallow of yogurt or sauerkraut or kimchi sends an army of probiotics—do-good bacteria—to take up residence in your gut, warding off disease, obesity, and GI problems. Not so fast.
“Those microorganisms will not colonize and become part of your gut microbiota,” says Robert Hutkins, professor of food science at the University of Nebraska. “But if you consume a diet rich in fermented foods with live microbes every day, it becomes the near equivalent of having those microorganisms living there.”
What good does that do? For most microbes, the jury is still out.1