Low and high carbohydrate diets cut life expectancy, study finds
The observational study looked at the eating habits of more than 15,400 US consumers who provided information on their dietary habits as part of the Atherosclerosis Risk in Communities (ARIC) study between 1987 and 1989.
At the start of the study and again 6 years later, participants completed a dietary questionnaire on the types of food and beverages they consumed, what portion size and how often, which the researchers used to estimate the cumulative average of calories they derived from carbohydrates, fats, and protein.
The median follow up was 25 years and during this time 6,283 participants died.
The study found that that diets both low and high carbohydrates were linked with an increased risk of mortality. Low carb diets were defined as carbs contributing less than 40% of the individual’s energy intake, while high carb diets were those where carbohydrates accounted for more than 70% of energy consumption.
Moderate consumption of carbohydrates, at 50-55% of daily energy intake, was found to be associated with the lowest risk of mortality.
The researchers estimated that from the age of 50, people in the moderate carb group were on average expected to live for another 33 years. This was four years more than those with extreme low-carb diets, 2.3 years more than the low-carb diet grouping and 1.1 more years than the high-carb group.
Low carb diets have gained popularity in the US and Europe thanks to their association with short-term weight loss benefits. According to the study authors, “many” randomised controlled trials of low carbohydrate diets suggest beneficial weight loss and improvements in cardiometabolic risk. However, mortality risk has typically not been investigated, the researchers noted.
Positive impact of plants versus animals as carb replacement
The researchers suggested that people who follow this low-carb diet pattern frequently substitute foods that are high in carbohydrates with foods that are high in animal fats and proteins. Eating more plant-based proteins and fats instead of carbohydrates was not found to have a negative impact on life expectancy.
“Low-carb diets that replace carbohydrates with protein or fat are gaining widespread popularity as a health and weight loss strategy. However, our data suggest that animal-based low carbohydrate diets, which are prevalent in North America and Europe, might be associated with shorter overall lifespan 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 promote healthy aging in the long-term,” said lead researcher Dr. Sara Seidelmann, Clinical and Research Fellow in Cardiovascular Medicine from Brigham and Women’s Hospital, Boston.
The primary findings were confirmed in a meta-analysis on carbohydrate intake including more than 432,000 people from over 20 countries, the study authors noted. This revealed similar trends, with participants whose overall diets were high and low in carbohydrates having a shorter life expectancy than those with moderate consumption.
"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," said Walter Willett, Professor of Epidemiology and Nutrition at Harvard T. H. Chan School of Public Health and co-author of the study.
Source: The Lancet Public Health
Published online ahead of print: DOI: 10.1016/S2468-2667(18)30135-X
‘Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis’
Authors: Sara B Seidelmann, Brian Claggett, Susan Cheng, Mir Henglin, Amil Shah, Lyn M Steffen, Aaron R Folsom, Eric B Rimm, Walter C Willett, Scott D Solomon.
