Death by Carbs?

People who adhered to a diet low in carbohydrates but rich in animal-based fats and proteins increased their risk of death - especially by cancer - according to a study published in the Annals of Internal Medicine, led by Simmons College nutrition professor Teresa Fung.

This study is the first of its kind to demonstrate the link between different types of low-carbohydrate diets and mortality, Fung says. It also sought to determine the long-term impact of low-carbohydrate diets, which have been promoted as an effective option for weight loss and improving health.

Conversely, the study found that a diet low in carbohydrates but rich in plant-based fats and proteins was associated with a lower risk of mortality.

Fung, who teaches at the Simmons College School of Health Sciences, led the study with colleagues at the Harvard School of Public Health and Channing Laboratory, Brigham and Women's Hospital.

"This research indicates that all low-carb diets are not the same, and the differences have an indelible impact," Fung says. "One that is based on plant foods is a better choice than one that is based on animal foods."

The study is based on two cohorts of participants - more than 85,000 women enrolled in the Nurse's Health Study (ages 34 to 59) who provided dietary information for 26 years as well as more than 44,500 men enrolled the Health Professional's Follow-up Study (ages 40 to 75) who provided dietary information for 20 years. All participants included in the study were free of heart disease, cancer, or diabetes. The Nurses' Health Study is based at Channing Laboratory, Brigham and Women's Hospital, and the Health Professionals' Follow-up Study is based at Harvard School of Public Health.

In determining health risk, the study created low-carbohydrate scores for the women and men, based on a multiyear evaluation of their diet intake with a focus on the proportion of carbohydrates, fat, and protein - whether derived largely from animal- or vegetable-based sources.

During follow-ups with the men and women, the researchers found that those who had a diet made up of more animal-based sources and a low-carbohydrate intake scored higher for association with "all-cause" mortality and cancer mortality. Those who had a diet made up of more plant-based sources and a low-carbohydrate intake scored lower for association with "all-cause" mortality as well as cancer and cardiovascular mortality.

Participants with a higher animal low-carbohydrate score were heavier and were more likely to be smokers, whereas those with a higher vegetable low-carbohydrate score consumed more alcohol and whole grains. Variations in lifestyle and other dietary issues, such as smoking status, family history of colorectal cancer, aspirin use, and history of hypertension were controlled in the analyses.