So far in the Athlete Microbiome Series we have learned what the microbiome is, what factors may influence an individual's microbiome and the influence of the microbiome upon inflammation, gastrointestinal health, metabolism and mental health. If you want a recap, you can read Part 1 and Part 2.
Part 3- the final post of this series, will be tying everything you have learned thus far together. We will be taking you through athlete dietary and supplemental interventions you can utilize to help improve the health of your microbiome.
Nutritional strategies to optimize performance and recovery depend on the sport and goals for each individual athlete. These programs consider energy intake, macronutrient targets, fluid intake, nutrient timing and ergogenic supplements- but rarely these dietary programs address microbiota health. The research on the influence of diet on improving the diversity and health of the microbiome is well supported. In fact, studies have shown a rapid modification of gut microbiota after just 24 hours of a dietary intervention (4) . The most prominent dietary factors which may influence the health of an athlete's microbiome include macronutrient content, protein sources and processed foods. All of which may impact the diversity and population of specific strains of bacteria.
Strategies to increase energy intake are often at the forefront of athlete nutrition programs as the majority of athletes struggle to meet the caloric demands of high intensity training. A deficit in energy balance leading to Relative Energy Deficiency in Sport (RED-S) is a huge threat to athlete health and performance (6). In part 2 we expanded on how the microbiome can impact energy harvest and metabolism. For a 90 kg male consuming 2000 kCal diet, it is predicted that approximately 7-22% of the caloric turnover is influenced by the gut microbiota (6).
Typical athlete diets are high in protein, simple carbohydrates and lower in fat. High protein content can influence the diversity and variation of specific strains of bacteria in the microbiome (6), however the current data is conflicting. Some studies have shown an increased level of microbiota diversity with increased protein intake , and others have shown a negative relationship (6). It is likely due to protein sources and fiber intake which may impact the influence on microbial diversity. For example, short term consumption of a plant based diet can drastically improve the health of an athlete's microbiota (9). Plant based diets are high in dietary fibers, which provide energy to the gut microbiota when digested (6).
Nutrition for improving the athlete microbiome should emphasize fiber and resistant starch intake, plant proteins in a whole foods diet.
Athletes are among the highest users of supplements (6). The use of supplements in athletes is dependent on age, sex, sport and level of training/competition (6). However, when it comes to improving the health of an athlete's microbiome - dietary strategies must come first. Supplements to improve microbiota health are adjunctive to a good diet. Probiotics and omega-3s are a great starting point for improving the diversity and health of your microbiome.
In Part 2 of the Athlete Microbiome series, we discussed how exercise induced gastrointestinal (G.I) distress (diarrhea, cramping, nausea etc) is common in active individuals or athletes (9). An unhealthy G.I tract is more permeable to toxins and pathogens which can increase risk of illness. Intense physical activity can have a negative impact on the integrity of the mucosal lining of the GI tract and thus leave an athlete more susceptible to inflammation and immune system depression (9). This phenomenon explains why the majority of research on probiotics in athletes is focused on immune system modulation as an outcome.
A probiotic is defined by the World Health Organization as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (4). Unfortunately, the word probiotic is often utilized as a marketing tool, where there may not be an actual benefit to the host. As a consumer, it is important to be informed about supplements such as probiotics as the health benefits will depend on the specific strain and dose.
Various strains of bacteria commonly found in probiotic supplements such as Lactobacillus, Bifidobacteria and Saccharomyces have been studied to modulate immune function, help support the integrity of the intestinal lining and protect the gut from overgrowth of pathogens (not so good bacteria) (8). Lactobacillus species, being the most common of the three, have been shown to be effective at decreasing the severity and duration of upper respiratory tract illness (URTI) in athletes (8). A combination of Lactobacillus and bifidobacterium species probiotics were shown to decrease the severity and incidence of gastrointestinal symptoms in marathon runners (8). Finally, Saccharomyces boulardii supplements are used to treat traveler's diarrhea (8), a common occurrence in athletes who are travelling often for competition.
Minimal studies have looked at the relationship between the use of probiotics and performance. However one 2020 study used a Bifidobacterium longum species probiotic in mice they put through a rigorous 6-week endurance training program (3). They found that the probiotic group had greater endurance and grip strength compared to the control group (3).
Although there is not enough evidence to consider probiotic supplements an ergogenic aid, preliminary evidence is promising. The International Society of Sports Nutrition’s 2019 position stand on probiotics stated that improvements in immune and gut health are the most prominent and well supported benefits of probiotic supplementation in athletes (4)
The two main omega-3 Polyunsaturated Fatty Acids (PUFAs) found in humans are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (2). Both EPA and DHA can be synthesized by dietary α-linolenic acid (ALA) - however this process in the body is inefficient (1). Therefore, dietary or supplemental intake of EPA and DHA is recommended. Research has shown that supplementing with omega-3s has cardiovascular, anti-inflammatory, musculoskeletal and digestive health benefits (5). In athletes, 2 grams of daily omega-3 supplementation may enhance recovery, cognitive function and increase muscle protein synthesis (5). The most promising research to date surrounding the use of fish oil in athletes is for recovery. Fish oil supplementation can cause a reduction in perceived muscle soreness in the 2 - 72 hour period following intense exercise (7). In addition, there is some preliminary evidence on the use of fish oils to enhance performance. In one study using 3 different doses of fish oil, 6 grams of Omega-3 (2400 EPA, 1800 DHA) improved acute power production (vertical jump) in athletes (7).
Omega-3s may also impact the health of your microbiome (is there anything they don’t do?!). One study found that supplementing with omega-3s in an animal model protected the gut microbiota from the detrimental effects of being fed a high fat diet (2). The study concluded that there is potential for omega-3s to be used to support microbiota health as well as in treatment for gut microbiota changes associated with obesity (2). Another study highlighted a positive correlation with omega-3 supplementation and increasing butyrate short-chain fatty acid (SCFA) concentration (2). SCFA such as butyrate have anti-inflammatory effects in the gut (2).
In the Athlete Microbiome series we have learned that the microbiome is incredibly responsive to dietary and lifestyle factors and can play a role in athlete immune function, mental health, metabolic and inflammatory processes and digestion. A whole foods, high fiber, plant focused diet will support the diversity and health of the microbiome. In combination, the use of probiotics and omega-3s have been shown to have positive benefits on athlete health and the microbiome. Additional supplements such as resistant starches and prebiotics (inulin, FOS), L-Glutamine , digestive enzymes and antimicrobials are further options that may be useful to athletes struggling with digestive health. Coaches, parents, athletes and health professionals who are looking for a modern, evidence based approach to improving overall health and performance should consider focusing dietary and supplemental strategies on the microbiome.