Can Probiotics Prevent Colds?

Eating yogurt could be the key to staying healthy during the cold and flu season. Probiotics—the “good” bacteria found in yogurt and supplements—may help stave off colds and other upper respiratory tract infections, according to a new Cochrane review pooling data from 10 randomized clinical studies involving 3,451 participants. People who consumed probiotics for more than a week had 12 percent fewer respiratory infections than those who were treated for less than a week or given a placebo, the researchers reported, in the first systematic review to show this benefit of the immune-system boosters.

Upper respiratory tract infections—such as colds, sinus infections, pharyngitis, croup, and ear infections—are the #1 reason for doctor visits in the US. And most patients get the wrong treatment, the researchers report, because doctors typically prescribe an antibiotic, even though most respiratory infections, including colds, are triggered by viruses, which don’t respond to antibiotics. These worthless prescriptions account for up to 75 percent of all antibiotic use in countries like the US, the researchers report, and a major culprit in the growing threat of antibiotic-resistance superbugs. Here’s a closer look at the study.

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What are probiotics? The most common definition comes from the World Health Organization: "live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host." Also known as “good bacteria” or “friendly bacteria,” probiotics are similar to healthy bacteria naturally found in the human gut. Most probiotics come from two groups of bacteria, Lactobacillus or Bifidobacterium, each of which includes different species, such as Lactobacillus acidophilus and Bifidobacterium bifidus. A few common probiotics, such as Saccharomyces boulardii, are yeasts, not bacteria.

Where are probiotics found? Foods containing probiotics include yogurt, fermented or non-fermented dairy products, and soy products like miso, tempeh, and soy drinks. Another product that’s rich in probiotics is kefir, a drink made with cultures flavored with fruit. Probiotics are also available as dietary supplements.

What are they used for? People typically take probiotics to prevent gas, cramping and diarrhea sparked by antibiotics. Naturally, the gut contains about 400 types of probiotic bacteria that promote healthy digestion, but taking antibiotics kills off both harmful and helpful bacteria, leading to gastrointestinal side effects. The Cochrane Review reports that probiotics can help reduce or prevent antibiotic-induced diarrhea, by replacing the beneficial bacteria. Limited scientific evidence suggests that friendly bacteria may also be useful for combating other forms of diarrhea, irritable bowel syndrome, vaginal infections, and eczema outbreaks, reports the National Center for Complementary and Alternative Medicine.

Why do probiotics help prevent viral infections like colds? The Cochrane Review researchers theorize that probiotics may have two immune system-boosting benefits: fortifying the integrity of the gut wall and revving up activity of phagocytes, disease-fighters, such as white blood cells, that engulf and absorb bacteria and other foreign particles. While further research is needed to confirm this theory, researchers do know that gut bacteria play a key role in the immune system, so it makes sense that probiotics could help bolster the body’s natural defenses.

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