Everything you read on the Internet is not true, but you know this. While Google and other search engines are pretty good at sorting your search results so that the most reliable websites appear first, a new study cautions that when it comes to information about probiotics, most websites are linked to companies that sell them, a clear conflict of interest. Not everyone is aware of that.

Probiotics are big business. In 2017 they generated over $370 million in sales in the United States. The live organisms in probiotics consist of good bacteria and yeasts. They are supposed to help keep the digestive system healthy. These organisms occur naturally in the body as part of your microbiome, but sometimes they can get out of balance, and ingesting the microbes probiotics deliver is seen as a possible way to put things back in balance.

Since consumers rarely scroll past the first ten results of a Google search, researchers also looked at how the websites were ranked by Google.

Probiotics can be purchased as dietary supplements. They are also found in certain foods, such as yogurt and fermented foods like kimchi, sauerkraut, kefir, tempeh or kombucha. Probiotics in food have a better chance of reaching your intestines; many of those in supplements are rendered ineffective by stomach acid.

The health claims for probiotics extend beyond the digestive system. They are promoted to help with mental problems like depression, stress, anxiety and memory; offer improved heart health; reduce the severity of eczema and some allergies; aid in weight loss; and boost the immune system.

The range of these claims should be enough to make one skeptical. European researchers, concerned that consumers have unrealistic expectations about the benefits of probiotics, reviewed the first 150 websites that came up in a Google search for “probiotics.”

After noting where the webpages originated and the physical issues they addressed, the team, from the Institute for Interdisciplinary Innovation in Healthcare at Université Libre de Bruxelles, in Brussels, Belgium and the Brighton and Sussex Medical School in England, evaluated the scientific accuracy of the claims for probiotics using the Cochrane library, a database of evidence-based medical research. Since consumers rarely scroll past the first ten results of a Google search, researchers also noted how the websites were ranked by Google.

The most reliable websites usually end in .edu, .org, or .gov.

Most of the 150 websites that were studied were news outlets and commercial websites, and these presented the least reliable information. The side effects of probiotics were rarely mentioned nor were any regulatory issues addressed, and there was a lack of scientific documentation. Findings from mouse studies were used to make claims about the benefits of probiotics in humans in some cases.

“Google prioritizes webpages containing more complete and scientifically robust information about probiotics, particularly health portals, and these are given a higher ranking than commercial websites. However, the fact that there is such a large amount of commercially-oriented information is problematic for consumers who are searching for honest answers,” explained study author, Pietro Ghezzi, of the Brighton and Sussex Medical School, in a statement.

Despite Google’s having set some criteria for ranking health-related websites, people should always look into the sources of information they find online and question claims concerning health, nutrition and dietary supplements, not just probiotics. The most reliable websites usually end in .edu, .org, or .gov. Check to see that the information is written by a health professional, such as a doctor, nurse, dietitian or others working in the field of healthcare.

Content that comes from a company website that is selling a product could have biased information that is not in your best interest. Finally, make sure the information you are reading is no more than three years old because medical research is ongoing.

The study is published in Frontiers in Medicine.