The “good bacteria” may help healthy people but aren’t formally recommended.
Probiotics are “good” bacteria touted to help maintain digestive health and boost the immune system. You can take them in a dietary supplement or get them from food sources, such as yogurt. But should you? “They can be helpful in some cases, but we have relatively few studies to tell us if and when they are safe and effective for older adults,” says Dr. Patricia Hibberd, an infectious disease specialist at Harvard-affiliated Massachusetts General Hospital who’s investigating the safety of probiotics across the life span.
Microbes in the lower intestinal tract help us digest food, fight harmful bacteria, and regulate the immune system. But sometimes an imbalance of microbes occurs, leading to diarrhea and other health problems.
When the gut becomes unbalanced with unhealthy levels of certain bacteria, probiotics can help restore the balance. They’ve been shown to secrete protective substances, which may turn on the immune system and prevent pathogens from taking hold and creating major disease. “But we are only beginning to understand how probiotics may promote health,” says Dr. Hibberd.
Some studies that suggest if you take a probiotic while taking antibiotics, you’re less likely to get diarrhea caused by the antibiotic. Probiotics taken as a supplement may also reduce the number of colds you’ll have in a year.
Probiotics are commonly used to reduce gastrointestinal symptoms that are not due to acute illness, such as gas, bloating, and constipation. “But, again, we don’t have a lot of evidence to document that this works, particularly in older people,” says Dr. Hibberd.
Many types of probiotics are on the market. Some have been well studied, and some haven’t. One theoretical risk of probiotics, says Dr. Hibberd, “is if someone has an immune system weakened by illness or medication, that person could get sick from probiotics.”
Another concern about probiotics is that they’re considered dietary supplements, not drugs. As a result, the FDA doesn’t monitor the manufacture of probiotics. “It’s not clear if probiotics that can be bought at pharmacies and health food stores are high-quality products. It’s even possible that some lower-quality products may not even contain the probiotic bacteria that are listed on the label,” says Dr. Hibberd.
The best food sources of probiotics
Supplements aren’t the only way to get a daily dose of probiotics. There are many foods loaded with these cultures of good bacteria. The top sources include
Trying to get probiotics from food sources alone can be tricky. “Food manufacturers are not required to show a specific dose of a specific probiotic, so they don’t,” says Dr. Patricia Hibberd, an infectious disease specialist at Harvard-affiliated Massachusetts General Hospital. She says you might have a more consistent dose in a supplement, but advises that you speak with your doctor before beginning any probiotics regimen.
What you can do
Don’t start taking probiotics without talking to your doctor or pharmacist about whether probiotics might help you. People who have immune deficiency or are being treated for cancer should not use probiotics without a doctor’s okay.
The most common species of bacteria used in probiotics (among a potential 3,000 or so) are species of Lactobacillus or Bifidobacterium. The bacteria are usually freeze-dried (but remain alive); when you take the supplement, they warm up in your digestive system and become fully active. You can find probiotic supplements in most drugstores and supermarkets. They come as capsules or tablets to swallow and as loose powder to sprinkle on food. You’ll want a product that explicitly states a “sell-by” date. Dosages vary by product, so no general dosing recommendation can be made. However, common dosages for adults range from five billion to 10 billion colony-forming units per day. Take just one dose of probiotics per day.
Dr. Hibberd has observed in her studies that some people may experience diarrhea in the first few days of taking probiotics, but this goes away. She says taking probiotics at the end of a meal may help to reduce the symptoms.