“There is a proliferation of claims that probiotics — or prebiotics, which support the growth of these live microorganisms — promote digestive or immune health. Nearly every society has some form of them as a component of their basic diets, including yogurt, kefir, kimchi, and other fermented products. In addition, consumers spent $2 billion on probiotic supplements in 2017. But aside from reducing diarrhea in children and preventing the recurrence of certain gut infections, few of the medical benefits associated with probiotics have been scientifically proven. To bolster digestive health and immune function, eat a diet rich in fruits and vegetables and low in animal fats, food additives, and processed foods.” — Stephen B. Hanauer, medical director of the Northwestern Medicine Digestive Health Center