Low-carbohydrate diets have become increasingly popular as a weight-loss technique.
When individuals decrease carbohydrates in their diet, they typically replace the carbohydrates with plant or animal fat and protein. However, despite the popularity of this weight-loss strategy, it remains a hot topic of debate within the scientific community.
Lack of data on the long-term effects of low-carb diets
The low-carb diet, which often means an increase in the intake of protein or fat, has demonstrated its ability to induce short-term weight loss but many will argue that this is not enough to support its use as a weight-loss strategy.
There is a lack of data regarding the long-term effects of this weight-loss technique on health.
Before the study was published in The Lancet, mortality risk associated with a low-carb diet had not been extensively investigated due to the challenges this type of study would present. Inversely, published data from multinational and Asian studies reported increased mortality risk with high carbohydrate intake.
Researchers in Boston thus believed that this lack of data warranted further research.
During this prospective cohort study, the investigators included data from 15,428 adults from the Atherosclerosis Risk in Communities study who completed questionnaires between 1987 and 1989 regarding their diets.
The researchers examined the percentage of energy each adult was getting from carbohydrate intake and their all-cause mortality. The researchers also assessed the substitution of animal or plant fat and protein for carbohydrate and how this affected their mortality. These adults were followed up, on average, over 25 years and the results of the study were combined with the analysis from seven multinational prospective studies on carbohydrate intake.
Only low-carb diets with plant-based proteins were associated with lower mortality
The overall conclusion from this study was that both high and low-carb diets were associated with increased mortality, with the least risk observed with 50-55% carbohydrate intake. Low–carb diets with animal-derived protein and fat from sources such as lamb, beef, pork, and chicken were linked with higher mortality rates.
Interestingly, on the other hand, a low-carb diet that employed plant-derived protein and fat intake from sources such as vegetables, nuts, peanut butter, and whole-grain bread was associated with lower mortality.
Animal-based, low-carb diets should be discouraged, researchers say
The researchers of this study suggest that the source of food changes the association between carbohydrate intake and mortality, which provides further evidence that animal-based, low-carb diets should not be encouraged.
Conversely, restricting carbohydrate intake in combination with increased plant-based fats and proteins could potentially give a long-term strategy to promote healthy aging.
Reference: Seidelmann, S et al. 2018. The Lancet. [Online]. [2 October 2018]. Available from: https://www.thelancet.com/journals/lanpub/article/PIIS2468-2667(18)30135-X/fulltext
