What You Should Know About Probiotic Supplements
By Ana Schilke and Emeran Mayer, MD
“It has been generally assumed, but rarely proven, that these positive effects can be enhanced by taken probiotic pills.”
The human microbiome is composed of 3 major classes of resident microorganisms, bacteria, viruses and fungi. In an effort to maintain the delicate balance of this vast microbial ecosystem in our gut, and to restore such a balance after disturbing it through the intake of an antibiotic, many people have turned to probiotics which have become as popular as multivitamins and many other “health-enhancing” supplements. Many of these bacterial species, in particular those belonging to the class of Bifidobacteria and Lactobacillus reside in the adult digestive system in small numbers, where they aid in several beneficial processes such as digestion and nutrient absorption. It has been generally assumed, but rarely proven, that these positive effects can be enhanced by taken probiotic pills.
“…there is a small number of studies which have shown that certain probiotics are effective in reducing common digestive symptoms.”
According to the World Health Organization, “Probiotics are live microorganisms which when administered in an adequate dose confer a health benefit on the host.” This is an ambiguous definition, as it includes both the possible benefits of ingested microbes on gut and overall health in individuals without any specific gastrointestinal (GI) disorder (probably the majority of people who take probiotics), as well as the possible benefits in treating or preventing a specific disease (a small fraction of the overall market). Even though there are a number of clinical trials which have aimed to demonstrate an effect on GI disorders (most of which according to the report have not been conclusive, were of low quality or have been negative), there is a small number of studies which have shown that certain probiotics are effective in reducing common digestive symptoms such as rumbling and abdominal discomfort in otherwise healthy people. There is also recent evidence that the ingestion of a cocktail of probiotic organisms can improve metabolic health in patients with type 2 diabetes (see post by Colleen Cutcliffe, PhD). Unfortunately, for most probiotics such well-designed and controlled studies do not exist.
“The most common question I am being asked by patients and audiences is “which probiotic do you recommend for my gut health?”
Probiotics are consumed in many forms, whether it is in the form of fermented foods (originating from fish, vegetable or dairy) or in the form of pills. With an overwhelming number of different probiotic supplements being promoted online, in the health food section of markets and even in many doctor’s offices, it has become a major challenge for the consumer to sort through the products of a multibillion-dollar industry to identify the best option for our health. The most common question I am being asked by patients and audiences is “which probiotic do you recommend for my gut health?”
“…probiotics have little if any evidence-based value in treating digestive diseases including IBS and IBD.”
In seeming contradiction to many individual studies, a recently published report by the American Gastroenterological Association (AGA) on Clinical Practice Guidelines for the role of probiotics in the management of gastrointestinal disorders, based on an in depth Technical Review of the published literature concluded that probiotics have little if any evidence-based value in treating digestive diseases including IBS and IBD, a statement that is not surprising to somebody who has long followed the scientific debate about probiotics and who gets the question from nearly all of my patients which probiotic is best to take. The only digestive disease populations that the report exempts from their negative assessment were children and adults on antibiotic treatment, preterm infants with low birthweight and patients with pouchitis, a postoperative complication in patients following a colectomy.
If we accept that probiotics are beneficial for certain patients and certain individuals with a compromised gut microbiome, another question that I am often being asked by patients and audiences to my talks, should probiotics be taken via supplement pills? Is there any difference between the strains of bacteria found in these supplement options compared to simply intaking these microbes through fermented foods such as yogurt?
“…out of the sixteen supplements, only one matched what the label claimed.”
While the answers to these questions are not strictly black or white, it is important to know that most dietary supplements in the U.S. are not FDA (Food & Drug Administration) approved, which means they do not go through a rigorous evaluation of their quality or effectiveness. This leaves it up to the buyer’s discretion to decide whether what they are reading on the label is true. A recent study by the University of California Davis “Validating bifidobacterial species and subspecies identity in commercial probiotic products” used various DNA methods to test sixteen probiotic supplements that claimed to have certain strains of bacteria. Not surprisingly, the study concluded that out of the sixteen supplements, only one matched what the label claimed. Moreover, within each bottle of supplements, there was a large variation in the diversity of cultures even from pill to pill. Another often non-disclosed information is what percentage of the ingested microbes survive the transit through the harsh, acidic environment of the stomach. This large inconsistency between what is on the label, what is in the supplements and how much of that arrives in the large intestine intact is one of the main reasons why supplemental probiotics may not be the best option for promoting gastrointestinal health, but in many cases function as an expensive placebo pill.
On the other hand, a 2016 study by the Dairy Research Foundation in California determined naturally occurring probiotics containing live microbes, such as yogurt, have been proven to aid in overall digestion, specifically in the maldigestion of lactose containing foods. This is because yogurt that is considered probiotic contains the strains Bifidobacterium lactis or Lactobacillus casei, acidophilus, reuteri. While the positive effects of yogurt have been documented, even their help as a probiotic is limited.
“Consuming probiotic pills while being on such an unhealthy diet is unlikely to improve gut health.”
Perhaps the best way to promote a healthy gut is to look beyond just probiotics, and consider our diet as a whole, evaluating which foods we should consume and which foods we should make an effort to avoid. A recent scientific study “Influence of diet on the gut microbiome and implications for human health” published in the Journal of Translational Medicine evaluated different consumption of foods and their effects on the gut microbiome. As supported by a body of published literature, this study found that the consumption of high saturated fats, such as processed meats and butter, disrupt the gut microbial ecosystem in our gut, leading to increased inflammation and sensitivity. Individuals adhering to Western diets, in particular the standard American diet, typically consume substantial amounts of these animal-based fats (as well as sugar), together with low intake of dietary fiber and polyphenols. This diet has been shown to be associated with a reduced abundance of beneficial gut microbes and with poor gut health. Consuming probiotic pills while being on such an unhealthy diet is unlikely to improve gut health. On the other hand, reducing these kinds of foods in conjunction with eating natural probiotics such as yogurt would be an effective combination for a healthy microbiome.
Even though I generally agree with the conclusions of the AGA guidelines, there are several important points to consider before we close the curtain on the benefits of probiotics for gastrointestinal disorders:
- The same microbes may not be effective in everybody, and based on current knowledge, the effectiveness of a particular microbe is likely to depend on the unique composition and function of the gut microbiome of a particular individual. Until we are able to design custom cocktails of probiotic strains which match an individual’s microbiome and evaluate the effectiveness in such selected populations it may be impossible to demonstrate significant benefits in clinical trials.
- While in most people, orally ingested beneficial microbes are not able to colonize, e.g. make a permanent home in the gut of an individual, and are gone within 48 hours, they do persist in others. Again, we currently don’t know how to identify such individuals before deciding on a treatment.
- People have strong belief systems about probiotics, similar to such beliefs in multivitamins and supplements. Strong beliefs are often associated with powerful placebo effects which make it difficult in a clinical trial to identify a specific probiotic effect.
- Regular intake of fermented food, be it dairy, vegetables or fish dates back, and foods from fermented milk products date back about 8000–10,000 years and are popular in wide parts of the world. This implies that our gut has adapted to the presence of such exogenous microbes and derives a benefit from their consumption. It is likely that the combination of valuable nutrients contained in these foods (including dietary fiber, polyphenols, and, in addition to the fermenting microbes enhance the benefit of such fermented foods.
“…The regular intake of naturally fermented foods, be it yoghurt, kefir, cheeses, kimchi or kombucha should be part of any healthy, gut friendly diet…”
As we currently don’t have an easy and reliable test to determine who will benefit from ingesting a particular microbial strain, or a cocktail of multiple strains, I personally feel that the regular intake of naturally fermented foods, be it yoghurt, kefir, cheeses, kimchi or kombucha should be part of any healthy, gut friendly diet, a statement supported by longstanding dietary traditions around most parts of the world. These foods are not only tasty, but provide health benefits over and above possible microbe-mediated effects
Niv Smora et al. Personalized Gut Mucosal Colonization Resistance to Empiric Probiotics Is Associated With Unique Host and Microbiome Features. Cell 2018; 174:1388-1405
Ana Schilke is a neuroscience student at the University of California, Davis. Born and raised in Spain, she has always valued the importance of food and nutrition and its effects on the human body and mind, something that has driven her to pursue a career in medicine.
Dr. Emeran Mayer is a Distinguished Research Professor in the Departments of Medicine, Physiology and Psychiatry at the David Geffen School of Medicine at UCLA and the Executive Director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience at UCLA.