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* Corresponding author: H. L. Cheng, email [email protected]
Life history theory is an ecological and evolutionary framework grounded upon a central tenet that lifespan and reproduction trade-off against each other(1). Through this theory, the strong morbidity and mortality risks associated with earlier timing of pubertal onset or menarche may be explained as consequence of attaining reproductive maturity at a younger age(1). Earlier pubertal timing has, for many years, been recognised as a predictor of cardiometabolic disease, some hormone-related cancers and mortality(2). More recently, a link between faster pubertal tempo and suboptimal mental wellbeing has been described(3,4), suggesting that a trade-off potentially exists for the timing as well as speed of sexual maturation.
Over the past decade, there has been emerging interest in understanding how life history trade-offs are impacted by dietary macronutrients. Such interest has risen from advances in dietary analysis via nutritional geometry (NG), which is a non-linear data-driven analytic approach that considers how nutrient balance (rather than independent nutrient effects) relates to an outcome variable by ‘mapping’ data on a multi-dimensional space. Animal experiments using NG have generally found that a higher intake of protein relative to carbohydrate promotes fecundity, whereas the reverse dietary pattern prolongs survival(5–8). Such findings align with large epidemiological datasets on human ageing that show reduced mortality risk with high-carbohydrate, low-protein intake using the same analytic methodology(9). Studies of longevous populations around the world (e.g. Okinawans) also report dietary macronutrient ratios that mirror the lifespan-promoting diets in the animal experiments(10). The impact of macronutrients on human reproduction is, by contrast, less well explored. However, there is some evidence to suggest that the facilitatory effect of higher-protein, lower-carbohydrate intake on reproduction, as shown in the animal experiments, may hold true for pubertal maturation in humans.
Several cohort studies, primarily from the 1990s and mostly in girls(11), have reported that higher total and/or animal protein intake in childhood predicted earlier timing of pubertal events including height take-off, thelarche and menarche(12–16). Yet, the overall evidence is equivocal because a number...