4.3 Gut Microbiome
As mentioned previously, the gut microbiome includes all the microbes that reside in the colon or large intestine. Recently, scientists have discovered that these microbes are related to many aspects of human health including metabolism, weight, body composition, disorders of the GI tract, immune function, risk of chronic disease, and may even be linked to mental health. As the gut microbiome is an emerging area of research, there are many things that we don’t know about it. This might be the missing piece as to why there is so much unexplained variation between individuals. The gut microbiome can actually be considered an organ because it is involved in many physiological processes necessary for our survival.
Even though there are many unknowns about the gut microbiome, it appears to be influenced by the foods we eat, our stress levels, environmental exposures, alcohol intake, antibiotic use and even exercise habits. However, there is no clear cut “perfect” microbiome to strive for. At this point, increased microbial diversity is equated with good health while ongoing research examines the effects of specific strains of bacteria. We know that the bacteria in the gut ferment soluble fibers (found in non-processed plants) which are not digested and absorbed in the small intestine and these soluble fibers can be converted to short chain fatty acids which can be used to reduce inflammation in the colon and keep the colon cells healthy (1). The consumption of refined carbohydrates, found in many processed foods, appears to disrupt the microbiome making it less diverse. High-protein or high-fat diets are also often associated with decreased microbial diversity, though it is debated whether this is caused by low-fiber intake or the presence of unabsorbed protein in the colon from excessive dietary protein intake.
Related to physical fitness, some recent studies suggest that athletes have more diverse microbiomes than their sedentary counterparts and endurance athletes tend to have different gut microbiomes than strength or power athletes (2,3). Research also suggests that baseline gut microbiota can predict performance in both cardiovascular and resistance exercise and isolating strains of specific bacteria from elite athletes’ fecal samples and inoculating these bacteria in mice guts led to enhanced aerobic capacity or strength in the mice (4). This may be related to being able to use short chain fatty acids produced by bacteria in the colon as another source of fuel during aerobic exercise (5). The gut microbiome also plays a role in recovery from intense exercise and may help mitigate the effects of overtraining syndrome.
So how can you ensure that you are keeping your gut microbiome healthy? Maybe you’ve heard about probiotic supplements or functional foods that contain healthy bacteria. Unfortunately, probiotics are regulated under supplement law which, as was covered in chapter 1, has very little regulation. Many companies will market their products as the cure to all your problems but most probiotics you find on the market have no research at all on the specific strains of bacteria and dose they use in the product. Also, probiotics are live microorganisms. This means that if the product was shipped or stored incorrectly, the bacteria may have died in transit and offer no benefits. Functional foods like yogurt or other fermented foods do contain some live bacteria and may provide some benefits but studies currently show very mixed results. Right now, it seems like the best way to keep your gut microbiome healthy and diverse is by eating a diverse diet with plenty of non-processed plants high in fiber.
