A study in the August publication of the Lancet aimed to investigate the association between carbohydrate intake and mortality. The meta-analysis included 432,179 participants who were followed for a median of 25 years. The primary outcome was all-cause mortality. Researchers also assessed whether the substitution of animal or plant sources of fat and protein for carbohydrate affected mortality.
Both low carbohydrate consumption (<40%) and high carbohydrate consumption (>70%) conferred greater mortality risk than did moderate intake. However, results varied by the source of macronutrients: mortality increased when carbohydrates were exchanged for animal-derived fat or protein and mortality decreased when the substitutions were plant-based. Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favored plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality.