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Sports nutrition for the brain

There is a constant stream of information travelling from our brain to our exercising muscles to control pathways involved in energy intake, expenditure and storage. When these messages are disturbed, fatigue is thought to occur; a term commonly called ‘central fatigue’.

It is hypothesised that a disturbance caused as a result of an increase in central ratio of the neurotransmitters serotonin to dopamine is associated with feelings of tiredness and lethargy, accelerating the onset of fatigue.

Carbohydrate

Carbohydrate is well known to improve prolonged exercise however, it may also have a direct influence on the brain. The amount of free-tryptophan, which once entering the brain is converted to serotonin and increases feelings of fatigue, may be reduced with the ingestion of carbohydrate. Carbohydrate supresses lipolysis, lowering circulating concentrations of plasma fatty acids and limiting the exercise-induced rise in free-tryptophan. Carbohydrate feeding during exercise may also cause increased delivery of fuel for the brain.

BCAA

Branched chain amino acid (BCAA) supplementation has been used to try and influence the levels of serotonin in the brain and consequently fatigue. However, there is limited evidence to suggest that either exercise capacity or performance can be enhanced by nutritional manipulation of BCAA. However, there is some evidence to show BCAA ingestion influencing ratings of perceived exertion and mental performance.

Take home message:

Central fatigue is a complex phenomenon. It is clear that the brain plays an important role in exercise performance however, whether this can be influenced by nutritional strategies, remains unclear. What is certain is that the complexity of the brain will make it very difficult to establish clear guidelines for interventions.

Supplement

Claim

Evidence

Carbohydrate

Increases energy to the brain and postpones fatigue Strong evidence

Branch chain amino acids

Postpones fatigue

No evidence in well controlled studies

Caffeine Improves performance

Mixed evidence. Dependent on responders and non-responders. No effect in the heat.