Dear Dr. Eva,

Do you think probiotics are helpful for getting rid of diarrhea and yeast infections?

Prefer Natural

Dear Natural,

There are several areas of the body which normally have large amounts of bacteria lining their surfaces. These areas include the vagina and parts of the gastrointestinal tract: the mouth and the colon (large intestine). The colon normally has over 400 different species of bacteria. These bacteria naturally live in our bodies, so we benefit from them without doing anything. Babies’ bodies are colonized by these healthy bacteria soon after birth. Because they are not harmful and can be helpful, these bacteria are called “probiotics.” They are considered to colonize, not infect, the body. If a woman has a stable population of lactobacillus in her vagina, she may be less prone to yeast infections. If she has a stable mix of healthy bowel bacteria, she is less likely to get bacterial forms of diarrhea, including C. difficile. This is a serious, sometimes deadly diarrheal illness that occurs mainly in people who have recently been hospitalized or have taken a prolonged course of antibiotics.

Capsules of dried, live probiotic bacteria have been available without prescription for years. Lactobacillus, derived from milk, is the most common type available. Combinations of multiple probiotic bacteria are also available. People take pills that contain probiotics because they think the pills will prevent disease or generally help keep them healthy. Twenty percent of US adults have taken probiotics. “Pre-biotic” pills, which contain food for probiotic bacteria, are available as well.

So … do they work?

There is good evidence that naturally occurring probiotics, the bacteria that grow naturally in our bodies, do keep us healthy and help us resist disease. There is still no good proof that taking probiotic pills does us any good. The research that has been done has conflicting results: some studies showed possible benefit, but many others showed no benefit. However, it does seem clear that taking probiotics is not harmful. It’s important to know that the strains of bacteria in probiotics do not colonize the gut – they pass through and are gone. The only way to use probiotics to change the bacteria in your gut would be to take them continuously.

I don’t recommend taking probiotics or prebiotics, because so far they have no clear demonstrated benefit. Some doctors and nurse practitioners do recommend them for people with frequent diarrhea or yeast infections. So far, the best evidence of benefit from probiotics shows that they can prevent bacterial diarrhea and can help diarrhea end sooner when it does occur.

Probiotics, like all nutritional supplements, are not regulated by the US Food and Drug Administration (the FDA) the way prescription medicines and many over-the-counter medicines are. That means that the companies that sell probiotics don’t have to prove that the ingredients listed on the label are actually in the pills. Investigation into this has shown that some pills sold as probiotics contain no probiotics at all. To borrow a quote from a scientific article, “Enthusiasm for probiotics has outpaced the scientific evidence.”

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Dr. Eva Hersh, MD
Dr. Eva Hersh, MD
Eva Hersh is a family physician. Send your comments and questions to her by email at