Directions for Future Studies to Determine Dietary Nitrate Efficacy in Female Athletes

INTRODUCTION Since the landmark discovery that a brief 3-d supplementation period of sodium nitrate can reduce the oxygen cost of submaximal exercise (1), numerous studies have investigated the effects of nitrate supplementation, andmany systematic reviews and meta-analyses show that it can benefit exercise performance and capacity (2,3). However, despite overall evidence in favor of its use as an ergogenic aid (2,3), a substantial proportion of the existing literature shows no benefit of nitrate supplementation on exercise performance and capacity-related outcomes (2), which suggests the existence of a substantial variation in response to its use. Many factors that can influence the ergogenicity of nitrate have been proposed, but perhaps one of the most interesting, albeit seldom investigated, is biological sex (2). In agreement with this notion, the results of two recent meta-analytic studies suggest that, although nitrate exerts a positive effect in men, its supplementation does not seem to benefit female performance, even in the face of evidence suggesting that women have a greater reduction of nitrate to nitrite than men (2–4). Nonetheless, some caution is needed in concluding that women do not benefit from nitrate supplementation; the small number of studies conducted exclusively with female participants (n = 6) and their heterogeneity in important methodological aspects (such as practices that control oral microbiota diversity, ingestion strategies, and exercise conditions) may have contributed to the lack of effect for women in these meta-analyses (2,3). Therefore, it is possible that these results are just a reflection of the small and limited literature on the ergogenic effect of nitrate in women.