Lead researcher Dr Sara Seidelmann of Brigham and Women’s Hospital in Boston says, “We need to look really carefully at what are the healthy components in diets that provide protection. Low-carb diets that replace carbohydrates with protein or fat are gaining widespread popularity as a health and weight loss strategy. However, our data suggests that animal-based low carbohydrate diets, which are prevalent in North America and Europe, might be associated with shorter overall life span and should be discouraged. Instead, if one chooses to follow a low carbohydrate diet, then exchanging carbohydrates for more plant-based fats and proteins might actually promote healthy aging in the long term.”

At the start of the study and again 6 years later, study subjects completed a dietary questionnaire on the types of food and beverages they consumed, and the portion sizes. They then estimated the average of calories they derived from carbohydrates, fats, and protein.

Previously published studies have shown low carbohydrate diets are beneficial for short-term weight loss and improve cardiometabolic risk factors. However, earlier studies have not looked into the source or quality of proteins and fats consumed in low-carbohydrate diets.

Analysis aimed at examining the difference between plant and animal based protein sources showed that replacing carbohydrates with protein and fat from animal sources was associated with a higher risk of mortality than moderate carbohydrate intake. Instead, replacing carbohydrates with plant-based foods was linked to a lower risk of mortality.Co-author of the study, Walter Willett, Professor of Epidemiology and Nutrition at the Harvard School of Public Health explains, “These findings bring together several strands that have been controversial. Too much and too little carbohydrate can be harmful but what counts most is the type of fat, protein, and carbohydrate”