Probiotics are foods or supplements containing healthful bacteria that pass to your colon when you eat them. The National Center for Complementary and Integrative Health reports that close to four million adults in the United States use probiotics for weight loss, gastrointestinal conditions, asthma, infections, eczema, depression and various other conditions, but a lead article in the Journal of the American Medical Association (March 3, 2020;323(9):823-824) advises that you should be concerned about buying and taking probiotic supplements because of:
• lack of high-quality data supporting benefits from taking probiotics;
• concerns about industry-supported, prejudiced studies and reviews;
• lack of regulation by any government agency on the production and sale of probiotics; and
• very real concerns about the possible harmful effects of probiotics.
The U.S. Food and Drug Administration (FDA) has not approved any probiotic products as treatments for disease (FDA.gov News and Events, Aug 16, 2018). Controlled studies that used gut biopsies rather than analysis of stool samples showed that while some patients appeared to benefit from probiotics, others had little response or had potentially adverse reactions to the supplements (Cell, Sept 6, 2018;174 (6):1388; 1406-1423).

The Difference between Good and Bad Colon Bacteria
You have more than 100 trillion bacteria in your colon that help to regulate your immune system that kills germs and repairs injured parts of your body (PLoS Biol, Aug 2016;14(8):e1002533). Healthful colon bacteria are content to eat the same food that you do and convert soluble fiber in plant foods to short chain fatty acids (SCFA) that help to prevent diseases and prolong lives by lowering high blood sugar, high blood pressure, high cholesterol, and chronic inflammation.

On the other hand, the harmful bacteria are not happy to eat the same foods that you do. Instead, they try to penetrate and enter your colon cells, and your immune system responds by producing lymphocyte cells and cytokine chemicals that try to kill germs (Int J Mol Sci, Apr 2015;16(4):7493-7519). If colon bacteria keep on stimulating your immune system, they cause chronic inflammation. The same lymphocytes and cytokines that work to kill invading germs can attack your own tissues to cause auto-immune diseases, punch holes in your arteries to increase your risk for heart attacks, and damage DNA to increase your risk for cancer.

What Probiotics May Do For You
A review of 45 scientifically-controlled studies published over the last 27 years (European Journal of Clinical Nutrition, March 26, 2018) showed that the use of probiotics in healthy people may:
• lead to an increase in healthful bacteria growing in your colon
• reduce belly discomfort caused by irregular bowel movements or constipation
• reduce the incidence of diarrhea and super-infections with a harmful bacteria called Clostridia difficile, if taken at the same time as a prescibed antibiotic (JAMA, 2018;320(5):499-500).

How Probiotics May Harm You
A recent article from University of Calgary in Alberta, University of Cincinnati College of Medicine in Cincinnati, and Washington University in St Louis School of Medicine reviewed some serious side effects from taking probiotics (JAMA, March 3, 2020;323(9):823-824). For example, they found an increased risk for bloodstream infections caused by Lactobacillus rhamnosus GG probiotic (Nat Med, 2019;25(11):1728-1732) and an increased death rate with use of probiotics to treat pancreatitis (Lancet, 2008;371(9613):651-659). Only two percent of the probiotic trials reviewed in this article reported efforts made to protect participants from adverse side effects (Ann Intern Med, 2018;169(4):240-247).

Congress Prevents the FDA from Protecting You
Legislation passed in 1994 prevents the U.S Food and Drug Administration (FDA) from regulating foods, and probiotic supplements are sold as food, not as drugs. The FDA has no central office to regulate the $64 billion industry, and consumers need to know that the industry is largely unregulated. Supplement labels are not supposed to include claims that the product can cure or treat specific conditions, so instead you will read that a probiotic “may help” to treat various conditions or that it “promotes the health” of your prostate, your brain, and so forth. The labels are required to say that the product “has not been evaluated by the FDA and is not intended to diagnose, treat, or prevent disease.” More elaborate claims and testimonials are given on websites and social media, and the FDA does not have funds to try to track down and regulate these ridiculous and unsubstantiated claims that probiotics cure all sorts of diseases.

Supplement sellers can block independent studies of their products by simply withholding documentation, such as by not permitting researchers to include proprietary information about a product (JAMA, March 3, 2020;323(9):823-824). An analysis of 384 randomized, controlled trials for probiotic, prebiotic, and symbiotic use (Annals of Internal Medicine, July 17, 2018) found that:
• 28% contained no harms-related data,
• 37% had no safety results,
• 80% did not include incidence of serious adverse events, and
• 98% included no definitions for adverse events, patient withdrawals because of these events, or the number of adverse events per study group.

Probiotics Will Not Fix an Unhealthful Diet and Lifestyle
Since bacteria in your colon eat the same food that you do, the best way to grow healthful bacteria is to eat a diet that encourages the growth of healthful bacteria. The term Prebiotics refers to foods that encourage the growth of healthful bacteria. Soluble fiber in plants now appears to be the most effective way to grow healthful bacteria in your colon, prevent disease and prolong your life. See The More Vegetables the Better.

My Recommendations
I believe that the best way to grow your colony of healthful colon bacteria is to eat a diet loaded with vegetables, fruits, whole grains, beans, nuts and other seeds. You increase the number of harmful colon bacteria in your colon when you eat the pro-inflammatory foods: red and processed meats, sugar added foods, all sugared drinks including fruit juices, and fried foods, so I recommend restricting these foods. I also recommend changing any of the other unhealthful lifestyle habits you may have, such as smoking, drinking alcohol or exposure to other environmental toxins, not exercising, or being overweight — particularly if you store excess fat in your belly and liver. Sad to say, aging also tends to increase your colony of harmful colon bacteria. We can try to combat this increase with more exercise and more vegetables.