A large new prospective study has reported that meat-based low-carb diets are linked to higher death rates from cancer and cardiovascular disease than vegetable-based low-carbohydrate diets. The study was designed to investigate the long-term associations between low-carbohydrate diets and mortality. The study followed 85,168 women from for 26 years and 44,548 men for 20 years until 2006 and included participants in the Nurses' Health Study and the Health Professionals' Follow-up Study. Study participants were initially without heart disease, cancer, or diabetes. Questionnaires were used at the outset and during follow-up to evaluate diets, including whether low-carbohydrate diets were animal-based (emphasizing animal sources of fat and protein) or vegetable-based (emphasizing vegetable sources of fat and protein).

A total of 12,555 women died (2,458 from cardiovascular-related causes and 5,780 from cancer) and 8,678 men died (2,746 cardiovascular-related and 2,960 cancer-related) during follow-up. Animal-based low-carbohydrate diets were found to be associated with a 23% higher rate of death from all causes (comparing those in the highest tenth of animal protein scores with those in the lowest decile), a 14% higher risk of cardiovascular mortality, and a 28% higher risk of death from cancer. On the other hand, a higher vegetable-based low-carbohydrate score was found to be associated with a 20% lower risk of death from all causes and a 23% lower risk of cardiovascular mortality. The authors note that the study has some limitations, namely that diet and lifestyle data collection involved some degree of error and that the participants were not a representative sample of the overall U.S. population.