Comparing the health effects of two diets over more than two decades, researchers from Harvard School of Public Health and the University of Singapore found consumption of a low-carbohydrate, vegetable-based plan resulted in reduced rates of death from cardiovascular disease and cancer, and a lower rate of all-cause death overall, whereas animal-based low-carbohydrate diet were associated with a higher risk for overall mortality.
"You can have the initial Atkins-type of low-carb diet, which is loaded with sausages, bacon, steaks, and you can have healthy versions of the low-carb diet with more vegetable- or plant-based protein and fat," said Dr Frank Hu, lead author of the study, published in the Annals of Internal Medicine.
"We looked at these two versions of low-carb diets and found that the impact of the two are drastically different," he added.
Low-carbohydrate diets – like the Atkins diet – claim to promote weight loss, improve cholesterol levels, and blood pressure.
Weight-loss trials have suggested low-carbohydrate diets to be as effective as other calorie restricted diets with higher carbohydrate content. However, the effects of animal-based and vegetable-based low-carbohydrate diets on mortality are uncertain.
The new study analysed two large, long-term cohort studies on diet and health – examining the relationships of animal-based and vegetable-based low carbohydrate diets and mortality.
Hu his team found overall that a low-carbohydrate diet was weakly associated with death from causes such as cancer and cardiovascular disease.
However, an animal-based low-carbohydrate dietary pattern increased risk of all-cause and cancer, whereas a plant-based low-carbohydrate dietary pattern lowered risks, particularly for CVD mortality
A direct association was observed between an animal based, low-carbohydrate diet and colorectal cancer death.
"Those who follow the animal-based low-carb diet have an increased risk of total mortality and cancer mortality in particular," noted Hu
The researchers concluded a vegetable-based low-carbohydrate diet “is probably healthier than an animal-based low-carbohydrate diet.”
The authors suggest this may be due to differences in micronutrient composition of the two diets.
“Low-carbohydrate diets from animal and vegetable sources may have similar major macronutrient content, but the source of the macronutrients can result in large differences in dietary components that may affect mortality, such as specific fatty acids, protein, fibre, vitamins and minerals, and phytochemicals,” wrote the researchers.
“The associations that we observed are more likely to be mediated by these bioactive components rather the carbohydrate content.”
An editorial for Annals of Internal Medicine, led by Dr William S. Yancy Jr from the Duke University Medical Centre, stated: “The current state of the evidence is such that no one can legitimately claim that a low-carbohydrate diet is either harmful or safe with any degree of certainty until a large-scale, randomized study with meaningful clinical end points is done,”
Source: Annals of Internal Medicine
Volume 153 no. 5, pages 289-298
“Low-Carbohydrate Diets and All-Cause and Cause-Specific Mortality”
Authors: T.T. Fung, R.M. van Dam, S.E. Hankinson, M. Stampfer, W.C. Willett, F.B. Hu.