For centuries, fermented foods have played a large role in many cultures. Ancient Greeks thrived on yogurt, ancient Chinese sipped on kombucha, Eastern Europeans craft sauerkraut, Koreans make kimchi and Middle Easterners whip up labneh or yogurt cheese. Fermented foods not only last longer but also typically have robust flavors and offer nutritional benefits from their live, active probiotic cultures. Fermentation creates an acidic environment that is hostile to harmful organisms, making food safer for consumption and boosting its longevity and possible health effects.
“We are really only starting to capture what role these traditional foods have played in cancer prevention, weight control and digestive health,” says Bethany Doerfler, MS, RDN, research dietitian in the Department of Gastroenterology at Northwestern Medicine. “Fermentation is an important way to preserve healthy foods, allowing for balanced diets in a growing world.”
The fermentation process starts with a carbohydrate-rich food (think barley for beer or grapes for wine) and combines it with a culture like bacteria or yeast. Most vegetables do not require an additional culture, just salt and water. The food is then placed in an airtight container until it becomes bubbly and flavorful. It takes patience, as the fermentation process can take days or weeks.
What is fermentation? A chemical reaction in which sugars are broken down into acids or alcohol. This process allows beneficial bacteria (aka probiotics) and digestive enzymes to prosper, which can enable better absorption of nutrients.
A probiotic, as defined by the World Health Organization, is a microorganism that has been shown to benefit the host who is ingesting it. The probiotic has to be live and active in order to be effective.
Many fermented foods contain live, active probiotics, but not all do. “Just because a bacterium or yeast is added to another product does not make it a probiotic,” says Darren M. Brenner, MD, assistant professor of medicine and surgery in the Department of Gastroenterology at Northwestern Medicine.
Probiotics can benefit human health in many ways, Brenner says. “They colonize the gut, which decreases space for pathogenic or disease-causing bacteria, as well as secrete chemicals to degrade bacterial toxins, interact with the immune system of the gut lining, play a role in motility and digestion, and [they] are responsible for the production of many vitamins and micronutrients such as vitamin K, folate and short-chain fatty acids.”
Fermented foods may have prebiotic benefits, too; meaning they provide food for the good bacteria and help create a favorable environment for probiotics. Fermented foods can have both prebiotics and probiotics. “It’s likely due to the unique matrix of dietary fiber that fermented foods can offer both the prebiotic base and the probiotic culture,” Doerfler says. A favorite for Doerfler is kefir, a cultured yogurt drink, because it’s lactose free; has calcium, B vitamins and more live, active cultures than most yogurts and is well-tolerated.
Just how much fermented food do we need to eat to get the benefits? “More studies are needed to better understand how to dose fermented foods for desired outcomes,” Doerfler says. However, there is more of a benefit from eating probiotic-rich foods than popping a probiotic pill, she says.
Consider adding fermented foods like kefir, kombucha, kimchi, sauerkraut, tempeh and miso to your diet. Your body—and its bacteria—might just thank you.
Victoria Shanta Retelny, RDN, is a lifestyle nutritionist and author of Total Body Diet for Dummies. Follow her @vsrnutrition.
Erin O’Donnell is a freelance health and science writer, parent, and graduate of Northwestern’s Medill School of Journalism. Walks by Lake Michigan make her happy.