Chronic ketogenic low carbohydrate high fat diet has minimal effects on acid–base status in elite athletes

Although short (up to 3 days) exposure to major shifts in macronutrient intake appears to alter acid–base status, the effects of sustained (>1 week) interventions in elite athletes has not been determined. Using a non‐randomized, parallel design, we examined the effect of adaptations to 21 days of a ketogenic low carbohydrate high fat (LCHF) or periodized carbohydrate (PCHO) diet on pre‐ and post‐exercise blood pH, and concentrations of bicarbonate (HCO₃ ⁻) and lactate (La⁻) in comparison to a high carbohydrate (HCHO) control. Twenty‐four (17 male and 7 female) elite‐level race walkers completed 21 days of either LCHF (n = 9), PCHO (n = 7), or HCHO (n = 8) under controlled diet and training conditions. At baseline and post‐intervention, blood pH, blood [HCO₃ ⁻], and blood [La⁻] were measured before and after a graded exercise test. Net endogenous acid production (NEAP) over the previous 48–72 h was also calculated from monitored dietary intake. LCHF was not associated with significant differences in blood pH, [HCO₃ ⁻], or [La⁻], compared with the HCHO diet pre‐ or post‐exercise, despite a significantly higher NEAP (mEq∙day⁻¹) (95% CI = [10.44; 36.04]). Our results indicate that chronic dietary interventions are unlikely to influence acid–base status in elite athletes, which may be due to pre‐existing training adaptations, such as an enhanced buffering capacity, or the actions of respiratory and renal pathways, which have a greater influence on regulation of acid–base status than nutritional intake.