By Dr. Matt Higgins (PhD), University of Northampton
In a recent BJSM editorial Dr Peter Brukner discussed the need to challenge two core strategies often adopted within the field of sport and exercise nutrition. The first tenet, that thirst is not a good indicator of hydration and that an individual must drink lots of fluids before, during and after exercise, has been vigorously challenged in the literature. Indeed, there is strong evidence that drinking to thirst, as opposed to prescriptive intake, is the safest drinking strategy during endurance exercise. Furthermore, it has recently been demonstrated that dehydration did not affect physiological or perceptual variables or indeed endurance exercise performance in the heat (e.g. 33°C, 40% relative humidity) (go HERE to read more). Therefore, on the balance of available evidence, particularly that not funded by organisations with a commercial interest in promoting fluid intake, consuming fluids beyond thirst, particularly during endurance exercise, appears at best erroneous and at worst catastrophic (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2564296/).
The second tenet of (sports) nutrition challenged was whether the optimum macronutrient intake for weight control, general health and athletic performance consists of low fat, high carbohydrate. With the obvious global obesity epidemic this is a clearly justifiable challenge. At the end of the editorial Brukner wrote: “…We need to determine once and for all whether our profession’s universal recommendation of a low fat high carbohydrate diet is the correct one…” In my opinion the scientific community, in particular sport and exercise nutritionists/dieticians, need to be careful not to demonise a particular (blend of) macronutrient(s). Indeed, a recent article discussing the efficacy of various diets with different blends of macronutrient intake suggests that:
“…The only consistent finding among trials is that adherence—the degree to which participants continued in the program or met program goals for diet and physical activity—was most strongly associated with weight loss and improvement in disease-related outcomes…” Furthermore “…The long history of trials showing very modest differences suggests that additional trials comparing diets varying in macronutrient content most likely will not produce findings that would significantly advance the science of obesity…”
Whilst from a public health policy perspective the attractiveness of universal nutritional recommendations is obvious, the evidence suggests that a one-size fits all policy for nutritional intake is unlikely to be unilaterally effective in reducing global obesity or indeed optimising sport and exercise performance. Therefore, if progress is to be made in terms of informing individuals of the blend of macronutrient intake that is optimal for them, more research is required focussing on the biological, behavioural, and environmental factors associated with adherence to nutritional intake and physical activity. In summary, whilst Dr Brukner has raised valid challenges to two long-held tenets of sports nutrition, where optimal macronutrient intake is concerned, it is important not to swap one myth for another.
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Dr Matt Higgins is a lecturer in sport and exercise physiology at the University of Northampton. He is research active in the areas of sport and exercise nutrition and has published several journal articles evaluating the efficacy of various nutritional ergogenic aids.
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