Fermentation is a case of what’s old is new again — an ancient food-processing method turned hot trend, with companies churning out products incorporating kefir, kimchi, sauerkraut and kombucha that are promoted as being probiotics. But do these foods offer true probiotic benefits? The short answer is probably not. But that doesn’t mean these foods are without benefit. First, let’s clear up what “probiotic” means. Scientists define probiotics as live microorganisms (microbes) which, when administered in adequate amounts, confer a health benefit. Probiotics can contribute to digestive and immune system health and crowd out harmful microbes in the gut (large intestine). They also create some nutrients, including vitamin K and many of the B vitamins, and help our bodies absorb other nutrients. However, most fermented foods do not meet these criteria, and would not give you the same benefit as a probiotic supplement might. Robert Hutkins, a food science professor and researcher at the University of Nebraska at Lincoln and author of “Microbiology and Technology of Fermented Foods,” said that most microbes — which include fungi as well as bacteria — in fermented foods have not been ch...