Diarrhea: Can probiotics help?

Probiotics - including lactic acid bacteria in particular - can make diarrhea stop about one day earlier. In rare cases they can lead to serious infections in people who have very weak immune systems.

Diarrhea is often caused by an infection. In industrialized countries, life-threatening cases of diarrhea have become uncommon. For mild diarrhea, simply drinking plenty of fluids so you do not dehydrate and waiting for it to run its course is often enough. However, small children and older people can quickly become so dehydrated that it becomes dangerous and special treatment is needed.

For mild diarrhea, some experts advise people to eat foods that have special microorganisms like bacteria or yeast in them. These are believed to reach the bowel and help the body fight the germs that cause diarrhea. Microorganisms like this are often called “probiotics”. The best known examples are particular lactic acid bacteria in yoghurts and other dairy products.

To find out whether or not probiotics really can help with diarrhea, researchers from the Cochrane Collaboration, an international network of researchers, systematically analyzed trials. The topic has been well studied: They found 63 trials, involving just over 8,000 people. The probiotics that were tested in the trials were taken in various forms, such as yoghurts, milk, special baby formula, powder or capsules. Most of the people were children who had had diarrhea for less than two weeks. The most commonly tested probiotics were lactobacillus casei, saccharomyces boulardii and enterococcus bacteria.

Current research results

Probiotics proved to be a useful additional option for people with diarrhea. In the trials where the length of diarrhea episodes was recorded, probiotics shortened the illness by one day on average. In some of the other trials, the researchers had counted how many of the people had no more diarrhea after a few days:

• They found that 63 out of 100 people who took probiotics no longer had diarrhea after three days (63%).
• Only 41 out of 100 people who did not take probiotics were free of diarrhea after three days (41%).

A different group of researchers tested whether probiotics help in children who have persistent diarrhea (diarrhea that lasts longer than two weeks). There is not as much research on probiotics in the treatment of persistent diarrhea: overall, the researchers only found 4 trials involving less than 500 children. But the results so far suggest that probiotics can also shorten the length of diarrhea episodes by a few days in children who have had diarrhea for longer than two weeks.

There were hardly any reports of adverse effects in these trials. The probiotic products were generally well tolerated. But in rare cases, in people who had very weak immune systems or particular serious illnesses, the probiotics led to infections. These included things like infections of the heart muscle or blood poisoning (septicemia).

An important question remains: products that are labeled 'probiotic' are available in various forms, including yoghurts, capsules and powders. And there are many different probiotic products out there. It is not clear whether they are all equally effective.

You can read more about diarrhea here.

Author: German Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care)