When I got my first job as a full-time dietitian, one of the perks my hospital offered was a generous supply of free supplements from our pharmacy. It seemed silly to turn that down, but I didn’t know what supplements to take. Probiotics were a hot topic, and I thought maybe they would be beneficial for my overall health. Now we know more about the gut microbiome and its importance to our health more than ever, so how do probiotics fit in?
In the not so distant past, the public perception of bacteria was that they were harmful. Techniques like pasteurization were developed to kill bacteria in our food to promote food safety. While we’ve all benefited from food safety, now we’re realizing that not all of those bacteria we were killing were harmful—some some of them were even beneficial. More recent work has found that about half the cells in our bodies are actually bacteria. It’s wild to think that only half the cells in our bodies are our own human cells.
With our growing understanding of the importance of microbes to our health, it’s no wonder that an industry has grown up to try benefit our gut microbiome. But with any new industry, the practices thought to be beneficial are changing as researchers make more discoveries.
Some health claims about probiotics are ahead of what research has uncovered and may not be totally accurate. For instance, a common misconception is that probiotic supplements can completely reseed good bacteria missing from a person’s gut. Probiotic supplements typically contain only one to a handful of species of bacteria, whereas a healthy gut has 500-1,000 different species.
The microbes that are the most abundant in a healthy gut are often different from those found in supplements. One of the most common species of bacteria found in supplements is called Lactobacillus, which is present in a healthy gut, but in lower abundance. One reason why Lactobacillus is common in probiotic supplements is because they are one of the few gut microbes that we know how to culture outside the human body. We do not yet know how to culture the majority of our gut microbes—especially those that are most abundant in a healthy gut—so these are not included in a supplement at this time.
Finally, most of the bacteria that we consume in food or supplements don’t survive our stomach acidity that’s needed to break down our food and prevent foodborne illnesses. This is why many dietitians recommend focusing more on eating prebiotic foods that contain the nutrients that feed good bacteria already present in your gut. It is also why hospitals are starting to use fecal microbiota transplants as a treatment to bypass the stomach barrier and go directly into the intestines of patients with a recurrent infection called C. diff.
With all that being said though, there are some conditions where research suggests that taking a probiotic supplement could be helpful. For example there is moderate quality evidence that taking probiotics can be safe and effective for preventing C. diff infection. Another example is a meta-analysis on irritable bowel syndrome (IBS) and the evidence to support the use of probiotics to aid in relieving symptoms, but the authors also urge caution with interpreting the results. Here’s a summary of what we know so far: http://usprobioticguide.com
What can you do?
Probiotics from foods and supplements can be helpful. But outside of probiotics what we know from the works of those like Rob Knight (a pioneer in the study of the human gut microbiome), is that people who eat a greater variety of plant species tended to have a healthier and more diverse gut microbiome. Another factor that might influence gut health is the number of fermented foods that you eat. Fermented foods have been a part of our diets for thousands of years as a means of preservation—some of these foods might seed your gut, but it’s also likely that they contain prebiotics that can help benefit your gut microbiota. In my own house we regularly eat fermented foods, such as sauerkraut, kimchee, homemade sourdough bread (pictured below), and cultured butter.
I’m hopeful that through ongoing research and with more advances in technology, probiotic supplements can be better tailored to reflect a healthy gut and better targeted for specific conditions such as cancer. For example, a promising advancement in probiotic delivery method, called microencapsulation, helps with probiotic survival. I’m looking forward to seeing new developments in this field, especially if we are able to culture other strains of bacteria that are present in a healthy gut microbiome.
If you think you need a probiotic supplement, check with your oncologist. Probiotics might not be right for patients who are immunocompromised, recovering from surgery, or are otherwise at high risk of infection. Your pharmacist can help you decide on the right dose as well as alert you to any medicine interactions.
If you decide to forego a probiotic supplement, know that most of us are okay simply focusing on more probiotic and prebiotic rich foods. The decision is up to you and your medical care team based on your past medical history and diet recall/history. Eating more species of plants is a great place to start!