Title: Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis
There continues to be a lack of clarity in the literature on the “best” or “healthiest” diet if such a thing even exists. Multiple diets have received positive attention such as the Mediterranean diet, DASH diet, low carb, low fat, weight watchers, Ornish and many more. Likely many are superior to the “average” diet.
However, curiosity continues to examine the breakdown of dietary macronutrients and their relationship with various health outcomes. Some dietary investigations focus on types of fat (saturated, trans, unsaturated), protein sources (animal, plant, etc) or macronutrients (fat, protein, carbs). Low carb diets have become popular for their purported weight-loss benefits. Previous studies have found both low and high carb diets are associated with increased mortality or death.
In this study, the authors looked at a large cohort of combined studies to evaluate the relationship between carbohydrate intake and mortality. They also evaluated the replacement of carbohydrates with plant and animal-based proteins and fats.
- In the first arm of the study, 15, 428 adults age 45-64 were enrolled in Atherosclerosis Risk in Communities (ARIC) study
- They completed a food frequency questionnaire
- The primary outcome: all-cause mortality
- They investigated the association between the percentage of energy from carbohydrate intake and all-cause mortality,
- The authors then performed a meta-analysis, combining the ARIC data with data for carbohydrate intake reported from seven multinational prospective studies
- They then assessed whether the substitution of animal or plant sources of fat and protein for carbohydrates affected mortality.
Average follow up time was 25 years, with 40,181 deaths of 432,000 total participants across all studies
Low carbohydrate consumption (<40%) and high carbohydrate consumption (>70%) conferred greater mortality risk than did moderate intake
Mortality increased when carbohydrates were exchanged for animal-derived fat or protein (HR 1.18, 95% CI 1.08–1.29)
Mortality decreased when the substitutions were plant-based (HR 0.82, 95% CI 0.78–0.87).
Interestingly, the safest diet consisted of carbohydrate intake around 50-55% of macronutrient intake.
Consuming <40% carbs or >70% carbs conferred a greater increased mortality risk.
Additionally, consumption of animal fat or protein (i.e. lamb, beef, pork, and chicken) increased mortality by 18% while consumption of plant-based fat or protein (ie. vegetables, nuts, peanut butter, and whole-grain bread) decreased mortality by 18%.
These findings are consistent with previous studies such as the nurse’s health study and health professionals follow up study.
In my opinion, this should prompt consideration of diet changes if you are an excessive carb consumer or excessive carb avoider. Furthermore, your non-carb sources of fat and protein should be primarily plant-based when possible.