Too much protein may lead to microbiome imbalance, impacting athletic performance

01 Aug 2022 --- Researchers from five universities reveal that loading up on protein or carbohydrates before an athletic event can lead to microbiome imbalance and directly affect performance. The study shows that loading up on carbohydrates improved the time-trials of highly trained runners while loading up on protein had the opposite effect.

Dr. Justin Roberts, associate professor, health and exercise nutrition, Cambridge Centre for Sport & Exercise Sciences, Anglia Ruskin University, explains the implications to NutritionInsight.

According to the research, dietary manipulation is a common practice among performance athletes. Acute shifts in dietary intake may have a direct influence on the athlete’s gut microbiome. High protein diets (HPD) may undermine microbiome stability and reduce performance, the findings reveal.

Carbs for the win?The gut-brain axis may affect the perceived exertion of an athlete during exercise.
The study included 16 high-performance runners and gave half of them a high-carbohydrate diet (HCD) and the other half an HPD for seven days before the events. It found that an acute shift in carbohydrate intake improved most runners’ trial times by 6.5% on average. However, adding a high protein diet for a short amount of time before an event decreased run times by 23.3% on average .

Roberts illustrates how an HCD from a variety of sources – including fruits, vegetables and fibers – could support stability and improve performance.

However, Roberts also notes that the effort perceived by athletes during intense exercise may also be linked to the microbiome via the gut-brain axis. This perception may also be a factor in athletic performance. 

Strike a balanceRunners who utilized a high-carbohydrate diet for seven days before an event improved their run times by about 6.5%The researchers analyzed 48 stool samples and found that HPDs and HCDs had opposing effects on performance. It asserts that athletes need to be aware of the possible consequences on microbiome balance as well, noting that HPDs reduced the amount of Bifidobacterium in the gut while Streptococcus was increased.

Bifidobacterium is one of the first bacteria to populate the microbiome at birth. It has been linked to stronger immune systems, the production of fatty acids and may even alleviate the symptoms of Irritable Bowel Syndrome.

Moreover, HCD showed a decrease in Streptococcus and increases in Collinsella and Lactococcus of which the latter is known to support immunity.

Roberts illustrates that the microbiome is both individualized for each person and highly complex. This study demonstrated that shifting a diet for seven days can have both positive and negative consequences for performance and microbiome balance. However, further research is needed to determine the long-term effects of these diets.

By William Bradford Nichols

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