Microbiome. Microbiota. Gut flora. Call them what you will, the teeming trillions of microorganisms coexisting with us, especially those in the gastrointestinal tract, are a vital part of our health. A growing recognition of this fact has boosted the popularity of fermented foods (e.g., yogurt, kefir, sauerkraut, kimchee and apple cider vinegar) as well as probiotics. Probiotic supplements provide “good” bacteria or yeasts that are said to enhance digestive, immune, cardiovascular and mood health, control inflammation and infections, help maintain healthy weight and bone density and more. What can you really expect from taking these concentrated doses of “bugs with benefits”?

Surprisingly, research evidence so far indicates that probiotics can indeed be useful for a diverse range of health conditions:

• Diarrhea due to antibiotic treatment: Antibiotics attack both and good and bad bacteria. This disrupts the normal microbial balance in the gut, allowing certain bad bacteria to grow unchecked and cause diarrhea. Probiotics can help prevent this distressing side effect by supplementing the good bacteria and rebalancing the intestinal flora.

• Irritable bowel syndrome (IBS): In IBS, a variety of factors can trigger a changed bowel movement pattern, bloating and abdominal pain. Probiotics can improve these symptoms by controlling unfriendly bacteria, strengthening the intestinal lining and influencing pain receptors in the gut.

• Ulcerative colitis: Specific probiotics can keep ulcerative colitis, an autoimmune inflammatory bowel disease, in remission longer.

• Colds and flu: Friendly gut bacteria stimulate the immune system to more effectively target disease-causing microbes, including cold and flu viruses. Probiotics can strengthen this immune support, helping to decrease the risk and severity of respiratory infections.

• Urinary tract infections (UTI): Probiotics may reduce the risk of UTI in women.

• Anxiety and depression: The gastrointestinal tract can communicate with and influence the function of the nervous system. Taking certain probiotics for several weeks has been found to improve anxiety, depression, stress and memory.

• Bone density: A strain of probiotic bacteria has been found to slow bone loss in elderly women.

• Cholesterol metabolism: Probiotic organisms may lower LDL cholesterol by breaking down bile and preventing its reabsorption from the gut as cholesterol.

• Diabetes: Some bacteria found in the colon and in probiotics produce short-chain fatty acids such as butyrate. These metabolites help regulate blood sugar metabolism and lower blood sugar and HbA1C levels in diabetics and prediabetics.

• Weight control: Certain probiotics can reduce fat absorption and storage, promote fullness and enhance calorie burning, thus facilitating fat loss and weight reduction.

Despite these impressive benefits, probiotics may not make an obvious difference in largely healthy individuals already maintaining a balanced microbiome. Although probiotics do appear to be safe for most people, individuals with immune deficiency or undergoing cancer treatment should check with their physicians before taking these supplements. Temporary, mild side effects such as gas and bloating may sometimes occur in the initial days of taking a new probiotic as the microbiome adjusts.

Probiotics differ from most other supplements in two key ways: the probiotic organisms must stay alive, and must reach the colon in order to be effective. Consequently, how well a probiotic product works is sensitive to factors including the following:

• Low product quality: Some probiotic products don’t actually contain all of the strains or colony-forming units listed on their labels, so it’s important to choose a reputable manufacturer.

• Improper storage: Many probiotics need to be stored cool and dry and refrigerated after opening to keep the microorganisms stable.

• Expiration: As time passes and especially after the expiration date, not enough probiotic organisms are likely to remain alive even with proper storage.

• Low stomach acid resistance: Stomach acid’s efficient killing of microbes is the main reason that billions of colony-forming units never make it to the colon. Some probiotic products use special coating technology or spore-forming bacterial strains to enhance their survivability.

In conclusion, current research does support probiotics’ benefits for a number of health issues, but further studies are needed to clarify them. Probiotic products appear harmless for most people, but can vary widely in quality and potency. It can also take time and daily dosing to experience any benefit from probiotics, and people’s responses are likely to differ. For a potential boost in the microbiome and overall health, probiotics are worth a try.