A wide body of evidence has shown that diet shapes the gut microbiome, and we can give our colony of beneficial gut micro-bugs a boost by feeding it more not-so-fresh foods.
After analyzing blood and stool samples of healthy adult participants, Stanford School of Medicine researchers found that a 10-week diet high in fermented foods (six servings daily) resulted in measurable improvements in microbiome diversity and decreases in markers of inflammation, suggesting the result was improved immune status.
This is noteworthy because science has found that healthy people typically have a more diverse microbiome than those suffering from chronic conditions.
Fermentation is a process in which microorganisms like yeast and bacteria break down food components, such as sugars, into other products, such as organic acids or alcohol. Historically, this has been used to extend shelf-life of items like vegetables and dairy.
Beyond the potential microbiome benefit, fermentation might generate bioactive compounds. It also creates new flavor compounds — why yogurt doesn’t taste like thick milk.
The optimal amount of fermented food intake is yet to be determined. But it appears that including one or more of these foods in your diet is good for the gut:
Yogurt — Fermentation makes this dairy easier to digest even for those with lactose intolerance. Make sure it includes live, active cultures.
Miso — Made from cooked whole soybeans combined with the bacteria “starter” koji, salt, and rice or barley, this umami-rich paste is great whisked into salad dressings or other foods.
Tempeh — Whole soybeans are soaked, cooked, left to ferment and pressed into a meaty patty. Marinate and grill it like steak, or crumble and use as a substitute for ground meat in chili, pasta sauces and tacos.
Sauerkraut — Submerged in a salty liquid for several days, cabbage slowly ferments into a crunchy, tangy condiment. To guarantee it has probiotics, look for the words “unpasteurized” or “raw” on labels.
Kefir — Most brands contain a higher probiotic count than yogurt, which accounts for its extra tang. Drink straight up, or use in smoothies.
Kimchi — This Korean staple is made when vegetables are mixed with a fiery garlic-chili seasoning and left to ferment for several days by lactic acid bacteria. Use as a topping for eggs, burgers, sandwiches, tacos and pizza.
Sourdough — Its tang comes from the old-school baking method of kickstarting fermentation with a bacteria- and yeast-rich starter.
Environmental Nutrition is an independent newsletter written by experts on health and nutrition.
