Cold potatoes—that is, taters that have been washed, cooked, and cooled—are one of the best sources of resistant starch. Resistant starch is a prebiotic, a type of indigestible carbohydrate that acts like food for gut bacteria, encouraging the good bugs to grow and flourish. While resistant starch has many health benefits, one of its most promising aspects is its ability to increase insulin sensitivity, helping people reduce diabetes risk and even lose weight.
Think of kefir as yogurt’s tangier but more powerful cousin. The drink is made by seeding milk with kefir “grains,” which are tiny bundles of yeast and bacteria, and letting it sit. Over time the grains ferment the milk, producing a tart drink full of probiotics, or healthy bacteria. A 2013 study found that kefir can help relieve gastrointestinal problems and allergies and may even have a positive effect on heart health. One caveat however: Many commercial kefir drinks contain very high amounts of added sugar, which feeds bad bacteria in your gut, so make sure you read the label and ingredient list. Find out everything you need to know about probiotic before you start taking them.