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Eating carbohydrates in moderation is optimal for health and longevity. The observational study of more than 15,400 people from the Atherosclerosis Risk in Communities Study (ARIC) in the USA found that diets both low (< 40% energy) and high (>70% energy) in carbohydrates were linked with an increase in mortality, while moderate consumers of carbohydrates (50-55% of energy) had the lowest risk of mortality.
The primary findings, confirmed in a meta-analysis of studies on carbohydrate intake including more than 432,000 people from over 20 countries, also suggest that not all low-carbohydrate diets appear equal-eating more animal-based proteins and fats from foods like beef, lamb, pork, chicken and cheese instead of carbohydrate was associated with a greater risk of mortality. Alternatively, eating more plant-based proteins and fats from foods such as vegetables, legumes, and nuts was linked to lower mortality.
Animal-based low carbohydrate diets might be associated with shorter overall life span replacing low carbohydrate diet with from more plant-based fats and proteins might promote healthy aging and longevity.
Previous randomised trials have shown low carbohydrate diets are beneficial for short-term weight loss and improve cardiometabolic risk. However, the long-term impact of carbohydrate restriction on mortality is controversial with prospective research so far producing conflicting results.
Researchers studied 15,428 adults aged 45-64 years from diverse socioeconomic backgrounds from four US communities. All participants reported consuming 600-4200 kcal per day for men and 500-3600 kcal per day for women, and participants with extreme (high or low) caloric intake were excluded from the analysis.
At the beginning of the study and after 6 years, participants completed a dinetary questionnaire on the types of food and beverages they consumed, what portion size and how often, which the researchers used to estimate the cumulative average of calories they derived from carbohydrates, fats, and protein.
The researchers assessed the association between overall carbohydrate intake (categorised by quantiles) and all cause-mortality after adjusting for age, sex, race, total energy intake, education, exercise, income level, smoking, and diabetes. During a median follow-up of 25 years, 6283 people died.
Results showed a U-shape association between overall carbohydrate intake and life expectancy, with low (less than 40% of calories from carbohydrates) and high (more than 70%) intake of carbohydrates associated with a higher risk of mortality compared with moderate intake (50-55% of calories).
The researchers estimated that from age 50, the average life expectancy was an additional 33 years for those with moderate carbohydrate intake-4 years longer than those with very low carbohydrate consumption (29 years), and 1 year longer compared to those with high carbohydrate consumption (32 years). However, the authors highlight that since diets were only measured at the start of the trial and 6 years later, dietary patterns could change over 25 years, which might make the reported effect of carbohydrate consumption on lifespan less certain.
In the next step of the study, the authors performed a meta-analysis of data from eight prospective cohorts (including ARIC) involving data from 432,179 people in North American, European, and Asian countries. This revealed similar trends, with participants whose overall diets were high and low in carbohydrates having a shorter life expectancy than those with moderate consumption.
Too much and too little carbohydrate can be harmful but what counts most is the type of fat, protein, and carbohydrate. The findings show observational associations rather than cause and effect. Considering evidence from other studies.