Can You Overdose on Probiotics? Risks and Side Effects

Probiotics seem to be everywhere you look these days. In addition to probiotic foods, like yogurt and kimchi, there are probiotic supplements and probiotic-bolstered products, from drinks and shots to cereal, chips, and chocolates. It begs the question: Can you take too many probiotics?

Here's what probiotics are, how they benefit your body, potential side effects and risks, and the best place to turn for guidance about how much to consume.

What Are Probiotics?

Probiotics are live microorganisms (microbes for short) that are intended to have health benefits when consumed. Many of the microbes found in probiotic products are similar to or the same as those that are naturally found in the human digestive system.

Probiotics include bacteria, such as Lactobacillus and Bifidobacterium, that benefit the body in various ways. Some probiotic bacteria help digest food or produce vitamins, while others kill off disease-causing cells.

Other potential probiotic benefits include preventing the growth of harmful microorganisms in the gut and reinforcing the gut barrier. The latter helps strengthen the walls of the GI tract to prevent compounds like toxins from being absorbed into the bloodstream.

A 2019 research review looked at 45 previously published studies on probiotic supplementation. In healthy adults, taking these supplements can lead to stronger immune system responses, better stool consistency, and healthier bowel movements, researchers concluded. Their review also linked probiotic use to improvements in female reproductive health, including an increase in beneficial vaginal bacteria.

Where Are They Found?

Probiotics are found in many forms, but technically they may not be in some of the foods you associate with probiotics.

For example, many people assume that fermented foods or beverages, which are made through the controlled growth of microbes, such as sauerkraut, always contain probiotics. But, in order for a food to meet the definition of probiotics established by the Food and Agriculture Organization of the United Nations and World Health Organization, the microbes must offer a health benefit.

Not all fermented foods include microbes that have proven health benefits. In other fermented foods, the microbes may not remain alive in the gut after being digested; and in some fermented foods, live microbes are destroyed by heat or pasteurization.

Generally, fermented foods that contain live microbes include:

• Traditional kimchi
• Fermented vegetables, such as unpasteurized sauerkraut
• Yogurt or kefir that says "contains live cultures" on the label

But again, these foods may not meet the formal definition of probiotics. They may contain amounts that are too low to provide the benefits demonstrated in clinical trials.

Most probiotics are sold as dietary supplements. These products don't require Food and Drug Administration (FDA) approval before they are marketed. But their labels cannot make specific health claims without the FDA's consent. If a probiotic is going to be marketed as a drug for the treatment of a disease, it must meet stricter requirements. This includes proven safety and effectiveness for its intended use through clinical studies and FDA approval.

What's the Right Amount?

The dose needed for probiotics varies greatly depending on the microbial strain and product, according to the World Gastroenterology Organisation (WGO). It is not possible to state a general dose; the dosage should be based on human studies showing a health benefit. In other words, the type and dose should match the research for a particular disease or condition.

For people with specific health conditions, published studies provide some guidance on probiotic species, strains, and doses that might alleviate their symptoms. But for healthy adults, there are currently no government guidelines or recommendations about the use of probiotics, including types or amounts.

Also, there is no standardization when it comes to products. You'll find a wide range of dietary supplements with various types and amounts of bacteria and a broad array of food products that have probiotics added. According to the WGO, the quality of probiotic products depends on the manufacturer.

Side Effects of Probiotics

Overall, probiotics have an extensive history of safe use in healthy people. Side effects of probiotics are usually minor, such as gas.

To date, though, few studies have looked at their safety in detail, especially over a long period of time. If you're an otherwise healthy person, it's probably safe to include probiotic foods, like live-culture yogurt, in your diet. But ask your healthcare provider before starting probiotic supplements.

Is it possible to take too much—or overdose—on probiotics? "Generally not," Matthew A. Ciorba, M.D., professor of medicine in the gastroenterology division at the Washington University School of Medicine in St. Louis, told Health.

"One may experience GI distress or bloating if taking too high of an amount, depending on the probiotic," Dr. Ciorba explained. But that wouldn't be considered an overdose.

That said, Dr. Ciorba noted that people who decide to take a probiotic supplement for their digestive health should weigh whether they're seeing any benefit, such as reduced GI distress. If not, it might not be worth the money.

Risks of Probiotics

The evidence to date suggests the risks of taking probiotics are greater in people with severe illnesses, HIV, recent surgery, or compromised immune systems, including people undergoing chemotherapy.

In some documented cases involving people who were severely ill or immunocompromised, the use of probiotics, which are live microbes, has been linked to blood infections that resulted in severe illness.

For this reason, probiotic use should be medically supervised for those with compromised immune function or other serious underlying diseases and only strains with proven benefits for a patient's condition should be used.

Dr. Cioba added that probiotic use should not be a substitute for conventional therapy.

Recap

Despite their popularity, there are no definitive guidelines for healthy people about the precise types and amounts of probiotics to take, including how much is too much. If you're a healthy adult, ask your healthcare provider for guidance, particularly regarding a probiotic supplement, and listen to your body to identify potential side effects like gas.

If you have a medical condition, work carefully with your doctor to identify which probiotic strains, if any, may be helpful for your specific condition based on published research, and use them under medical supervision.