By Brierley Wright, M.S., R.D. , September 28, 2012 - 11:49am
With cold and flu season just around the corner, our precautionary routine has shifted from sunscreen for skin protection to immune defense. There are so many immunity-boosting products out there, and the search for a natural way to enhance your germ resistance has potentially generated an almost endless list of possibilities. (Don’t be duped by these 4 immune-boosting myths busted .)
One increasingly popular trend is taking—or eating—probiotics, the live microorganisms found in fermented foods, such as yogurt, kefir, miso, tempeh and sauerkraut, and also available in supplements. But does it work?
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.
Related: 2 More Surprising Ways Probiotics Keep You Healthy 
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).
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Here’s the bottom line: Stick to probiotics from fermented foods (here’s an instance where you can feel good about bugs in your food!). 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.
Do you take a probiotic supplement? Tell us what you think below.