Here’s an instance where you can feel good about bugs in your food: probiotics—the live microorganisms found in fermented foods, such as yogurt, kefir, miso, tempeh and sauerkraut—may help your immunity.
In one study, participants who took a probiotic supplement (50 million cultures of Lactobacillus gasseri, Bifidobacterium longum and B. Bifidum) over two winter/spring seasons shortened any colds they got by about two days and lessened their symptoms, compared to those who took a placebo. Additional research—reviewed in Pharmacological Research—found that L. Casei (often added to yogurt) boosts T-cell production, our immune system’s specific, targeted line of defense. Scientists think probiotics help your GI tract’s natural bacteria to block pathogens from being absorbed.
Though the research is promising, we don’t fully know why certain strains work or how many we actually get in a product. (Yogurt labeled with the “Live & Active Culture” seal, however, guarantees 100 million cultures per gram—about 17 billion cultures in a 6-ounce cup, at manufacturing time.) Even if a number is listed, some of the probiotics may naturally die during storage or be destroyed during digestion. We also don’t know how many probiotics are needed to be effective (some say it’s the amount in a spoonful of yogurt, others say you need a cup).
Bottom Line: Stick to probiotics from fermented foods. You’ll get a dose of healthy bacteria plus other good-for-you nutrients (think: calcium in yogurt, etc.). Supplements might help, but they may not deliver the strain or dose promised.