Live microbes—probiotics—are generally considered to be good for gut health and for remedying other conditions. But how strong is the research?

Experts weigh in: While some studies provide evidence for these benefits, the science is not strong enough to recommend probiotics or to provide guidelines for their daily intake, says a recent review from the International Society for Probiotics and Prebiotics. Too many gaps in the research exist, and at this point the benefits are still hypothetical.

The researchers explain in their review that the early diet of humans included raw and unprocessed foods high in live microbes. It was not until the 19th and 20th centuries that foods became highly processed, sterilized and preserved. These changes eliminated many harmful bacteria from food…but at a cost. Foods without live microbes could weaken the gut’s ability to support the immune system, and this may lead to negative consequences.

Research suggests that the lack of different microbes (microbial diversity) may cause the gut’s immune system to become hypersensitive and may be responsible for the growing number  autoimmune diseases such as diabetes, multiple sclerosis and celiac disease. Some studies suggest a healthy and diverse community of microbes in the gut (the microbiome) is necessary for optimum immune health.

New recommendations: Gaps in the research on live microbes, gut health and the immune system are due to a short history of research on these topics, some poor research studies and the complex nature of the systems being studied. Before any guidelines can be recommended, the researchers call for enhanced studies to fill the gaps. Their recommendations are published in The Journal of Nutrition and include…

  • Gathering all the available evidence for a comprehensive review.
  • Enlisting researchers and scientists from respected organizations such as the National Institutes of Health, US Department of Agriculture and National Academy of Sciences.
  • Identifying the gaps in the science.
  • Designing large randomized and controlled trials to fill the gaps.

Only then, say the researchers, can conclusions be drawn on the benefits of live and safe microorganisms. Dietary recommendations for these organisms may then provide consumers with the information they need to benefit from probiotics and prebiotics. Although these microbes may not be critical for survival, they may offer opportunities for better health.

Source: Review titled, “Should There Be a Recommended Daily Intake of Microbes?” by Maria L. Marco et al., the International Scientific Association for Probiotics and Prebiotics, published in The Journal of Nutrition, December 2020.