Probiotics: Do They Actually Work?
A look at the potential perks of probiotics and other dietary supplements
—By Muneer Hasso
Bashir Kaspo, a sophomore who is prospectively studying neuroscience at the University of Michigan, usually enters his apartment with a desire for a meal. While what he eats depends on whatever cuisine he is craving on that day, there is one staple of his diet that he does not change.
“I usually take probiotics once a day around the time of lunch. I have been taking them since I was still in high school, around the time that I graduated, I think, so I figured that probiotics would help with all that, especially when I’d be going off to college soon and my diet would be changing.”
Brandon Askar, a senior at the University of Michigan who is studying cell and molecular biology, also takes probiotics on a regular basis. “I have been taking probiotics pretty much every day since around my sophomore year. My friend started to take them after he took a class on gut bacteria, so I kind of figured that I would start as well”.
Askar and Kaspo join many others who have started to take probiotics and other dietary supplements with the intention of boosting their gastrointestinal health. Scores of probiotics and other dietary supplements are available over the counter at nearly all pharmacies in America. These supplements are intended to boost an individual’s gut microbiome, an area of biological research and lifestyle applications that both have surged in popularity over recent years.
What Exactly is the Gut Microbiome?
The gut microbiome is the diverse collection of bacteria that reside in the large intestine. There are hordes of species of bacteria present in the large intestine, all of which have biological characteristics that can tolerate and thrive in the warm, anaerobic environment of the colon. The gut microbiota that make up each individual’s microbiome can differ quite significantly, with many different species being present in differing proportions.
The gut microbiome is heavily influenced and built during the first few years of life. The specific species of bacteria present also heavily depend on the mother. Research has shown that the composition of the gut microbiome is influenced both by the style of birth (traditional birthing vs section) and the manner of feeding (breastmilk vs formula). This dependence is a key factor in why the gut microbiome’s exact bacterial composition can vary from individual to individual. This variance from person to person sets the potential for possible health consequences both in the colon and across the entire body.
So How Does the Gut Microbiome Influence an Individual’s Health?
The gut microbiota has become commonly known to be living in a symbiotic relationship with their host organism, one in which both the bacteria and the host stand to benefit. They are able to break down starches and other molecules that are not digested in the host organism’s small intestine, producing metabolites that are absorbed into the body and used by the host organism in a beneficial manner.
Another interesting linkage between the health of the host and the gut microbiota is the potential correlation between bacterial diversity and the host’s weight, which has led to a spike in research done on this subject. Dr. Grace Chen, MD-PhD, a hematologist and oncologist in the University of Michigan Health System, interestingly notes that the gut microbiome studies have “transplanted an obese mouse’s gut microbiome into a germfree, non-obese mouse, and seen that the transplant receiver started to become obese”.
For a long time, researchers were left perplexed at what exactly is causing such an innate difference in obesity levels. The cutting-edge gut microbiome research sheds a light onto what may be causing obesity. In fact, it is now almost certain among biologists that the gut microbiome’s composition is implicated to some degree in varying rates .
The gut microbiome also has a large amount of research that correlates its diversity with inflammation of the gut. Dr. Grace Chen’s lab works with mice that are genetically identical, with their only difference being their gut microbiome’s relative composition, or the relative amount of particular bacterial compositions. “We essentially take these two cohorts of mice and look for any inflammatory differences. As it turns out, our second cohort higher correlation with tumor growth and inflammation under the same conditions as the first cohort”, says Dr. Chen.
This research study, along with other research that has come before it, opens a new understanding of what contributes to the high rates of large intestinal inflammation. Colon cancer and Inflammatory Bowel Disease (IBD) have long troubled patients and physicians alike, with many cases occurring without a known cause. However, research has shown that there is a linkage between the gut microbiome’s composition and colon cancer cases, a big revelation in a field of biological study that did not gain much traction until recent decades.
In addition to long-term inflammation and disease, the gut microbiome is implicated in more acute but still potentially lethal diseases. Clostridium difficile, more commonly abbreviated as C diff, is a bacteria that infects the colon and causes severe gastrointestinal symptoms, especially in the elderly. This invasion is usually caused by an unhealthy imbalance in the gut microbiome, usually when antibiotics kill good gut bacteria, which creates a niche for C diff to cause trouble.
Interestingly enough, recent research trends in this field have led to the discovery that fecal transplants of healthy gut microbiomes into a C diff patient have therapeutic properties, often treating the infection. While gross to imagine, it shows the effect that the gut microbiome’s composition has on the health of its host.
The gut microbiota can also produce metabolites (products of the breaking down of molecules in the body) that the host needs but cannot synthesize themselves from molecules that the host cannot digest. These metabolites are involved in biological processes across the host organism’s entire body. For example, a recent study by two Harvard professors reveals that healthy microbiomes in the gut produce metabolites that are necessary for the fine tuning of a mammal’s immune response. The gut microbiome, as it turns out, influences more than just the colon, but has immense consequences throughout the entire body.
There are even studies that show a potential relationship between the gut microbiome and neurological disorders and diseases. Depression, once considered simply a mental mood, is now being looked at through more medical lenses. It turns out that the inflammation in the gut microbiome could have some correlation to depression, which had been linked to inflammation and the responsiveness of serotonin receptors in the brain. This only adds on to the scope of importance that the gut microbiome has in maintaining its host’s well-being.
These correlations introduce the idea that the gut microbiome, a part of the body that had been overlooked in research for years on end, has a larger effect on its host organism that previously thought. This revelation has resulted in the increased research that is being conducted to learn more about the properties of the gut microbiome, specifically the differences in bacterial relative composition from organism to organism.
The relative composition of the gut bacteria has a direct impact on the health of their host organism, according to Drs. Justin and Erica Sonnenburg, PhDs, in their book The Good Gut. This revelation over the past decade has caused a surge in probiotic use, with the amount of adults who use probiotics quadrupling between 2007 and 2012, due to the increased awareness in the health and lifestyle fields about the importance of maintaining a healthy gut microbiome.
So, What Are Probiotics? And do They Work?
Probiotics are any dietary product, whether it be a food or a dietary supplement, that contains cultures of “good bacteria” that are supposedly beneficial for your gut microbiome and digestive health. Probiotics can be found naturally or can be manufactured into supplements containing significant amounts of good bacteria cultures.
Many fermented foods, including yogurt, kefir, sauerkraut, and the Korean pickle Kimchi, have naturally large amounts of good bacteria cultures. Yogurt, for example, typically contains the bacterial culture Lactobacillus, a symbiotic bacterial genus, which is also found in the gut microbiome, that has been shown to fight inflammation and boost the immune system.
In theory, probiotics should be effective in boosting the diversity of the gut microbiome, and therefore improving both the digestive and general health of a person taking them. After all, it is taking good bacteria and putting them into the body, which should increase the relative abundance of that bacteria in the gut microbiome.
However, research surrounding the subject has been controversial. Says Dr. Chen, “There are many research studies with both positive and negative results surrounding the effectiveness of supplementary probiotics”, making it difficult for the average probiotic user to evaluate their worth.
This is not to say that probiotics do not work and should not be bothered with. At the very least, taking probiotics has no downside to your health, as the bacteria “tend to be considered to have anti-inflammatory effects in animal models”, per Dr. Chen.
Furthermore, research studies clearly show a significant relationship between the amount of bacteria ingested by humans and the health, strength, and diversity of the gut microbiome. In general, the more hunter-gatherer and the less sterile the food in a given ethnic culture, the healthier and more diverse their gut microbiomes tend to be. This relationship shows that there is indeed a linkage to intaking bacteria orally and a stronger, more diverse gut microbiome.
PhDs Justin and Erica Sonnenburg touch on this fact in The Good Gut. They comment that eating more fermented foods can only benefit the gut microbiome, which “reduces the risk of illness from food-borne and respiratory pathogens” (219). These bacteria, which are naturally anaerobic, as is required in fermentation, should be able to survive in the equally anaerobic environment of the large intestine.
Does this logic also apply to supplementary probiotics, however? Unfortunately, there is no solid proof that these trendy supplementary probiotics have any real effect on the diversity of the gut microbiome. This is also discussed in The Good Gut, where the Sonnenburgs state that “a one-size-fits-all model does not apply to probiotics”(219). While the bacteria may be anti-inflammatory ex vivo (tissue studies), there are other variables that apply inside a live organism. Per the Sonnenburgs, not all probiotics have the same effect on every person. This could be attributed to the large degree of variance between the relative abundances of each organism’s gut microbiome.
Unfortunately, there is some evidence that the craze over probiotic supplements may just be a case of good marketing by the health and lifestyle industries. The Sonnenburgs make an important point when they discuss that probiotics are only loosely regulated by the FDA, which can lead to excess, and potentially exaggerated, advertising about the potential impact these probiotics may have on a person’s digestive health. All people have different microbiomes and will be affected differently, so it cannot be concluded as of now whether probiotic supplements actually make much difference for a person’s health and well-being. So while there may be no harm in taking probiotics, with a good upside, it should not be considered a guaranteed boost of the gut microbiome.
So, What About Other Supplements?
There are other supplements available that are also targeting at boosting the gut microbiome’s health and diversity. A prevalent supplement available are dietary fiber supplements. Most people have been told how important it is to get the recommended daily allowance of dietary fiber from their diets. And while it has been known that these fibers help the digestive system, the cause was never determined until the recent research of the gut microbiome became more prevalent.
Much research has been done on taking resistant starch (RS) and the resulting effect on the gut microbiome. In fact, a recent study shows a correlation between taking starch supplements and changes in the gut microbiota’s relative abundance. Based on numerous previous research, it has been shown that good bacteria can break down this starch into short chain fatty acids, such as butyrate. These metabolites are important for humans, as they are linked to potential anti-inflammatory effects in the colon, as butyrate is the major source of energy for colon cells.
While these fibers are not as well-researched or popular as probiotics, there is a clear potential benefit in taking RS supplements. It is known that these starches will reach the colon to be broken down by good bacteria, which is reason enough to consider taking them and justifies the common availability of starch supplements in many pharmacies and grocery stores.
So What Does This All Mean?
While the science is still working to prove the efficacy of probiotics, and to some extent starch supplementation, it is important that health culture is becoming more focused on the health and stability of the gut microbiome. These trends indicate that the increased research over the past decades surrounding the gut microbiome are translating into the health and lifestyle industries. People are starting to pay attention to their gut health as it is becoming increasingly more apparent that those bugs living in the gut are doing more than what was previously thought.
Feature Image Taken By Muneer Hasso