Probiotics are living bacteria or other microorganisms that have beneficial health effects in people when they’re ingested. The concept has become very popular and many of my patients are taking probiotics to gain some health advantage, but enthusiasm for a concept is not the same as scientific proof of effectiveness. Very few marketed probiotics have had their health benefits investigated scientifically, and of the ones that have been studied the reasons that they are of benefit are obscure.
Recently, Eamonn Quigley, MD, Chief of Gastroenterology and Hepatology at Houston Methodist Hospital, came to Baylor University Medical Center at Dallas for our internal medicine Grand Rounds discussion, where we discuss the latest developments in medicine to better serve our patients.
Dr. Quigley pointed out that the diversity of the microbiome, the collection of germs that inhabit our gut, is linked to our diet, health status and age. The germs that live in our gut play an important role in training our immune system, metabolizing what we eat and affecting how our body works. Studies in animals (where conditions can be manipulated experimentally) show that changes in the gut microbiome can have profound effects on body function and susceptibility to disease.
Studies in humans suggest that the microbiome may be important in the development of metabolic diseases, such as obesity or diabetes, and in the defense against gut infections, such as colitis due to Clostridium difficile. It may play an important role in inflammatory bowel diseases, like Crohn’s disease, and irritable bowel syndrome.
According to Dr. Quigley, your overall health may depend on the healthy diversity of your microbiome, since the germs that populate the digestive tract play a major role in digestive tract function. Scientists like Dr. Quigley who are involved in the field also are trying to identify—at a fundamental level –what makes an organism a “good” organism rather than just an “innocent bystander” in our intestine. It may be that it is the entire ecosystem that determines the impact of the microbiome on our health rather than the presence of any one specific organism.
Most probiotics lack research to back health claims
The idea that the billions of germs living in our intestines do us some good is a great concept, but proof that ingestion of specific probiotic strains has any health benefit is lacking for most marketed agents. Some of the agents sold may not even have living bacteria in them; they are not regulated as drugs by the Food and Drug Administration and do not have to be of proven value to be sold. Most of the studies that have been published are small studies in small groups of patients, and they are not necessarily conclusive. Relatively few strains have been studied in any detailed way, and most seem to have limited effectiveness in managing specific disorders. Problems that may benefit from probiotics include irritable bowel syndrome, antibiotic-associated diarrhea, and bloating.
Nevertheless, some individuals obtain great benefit from specific probiotics. Since there is little harm and rare serious complications from using probiotics in generally healthy people, it makes some sense to try one if you have a digestive problem that might benefit from treatment. Be cautious though: probiotics are not interchangeable; don’t assume that all have identical effects. It is wise to talk to your doctor about which probiotic might give you the digestive health that you’re seeking.