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Quality of low-carb, low-fat diet impacts mortality risk
Overall, low-carbohydrate and low-fat diets do not affect mortality risk; however, the quality of foods consumed as part of these diets could impact mortality risk, according to a study published in JAMA Internal Medicine.
“Our findings show clearly that the quality rather than the quantity of macronutrients in our diet has an important impact on our health,” Zhilei Shan, MD, PhD, research fellow at Harvard T. H. Chan School of Public Health, told Healio Primary Care. “People who eat healthy low-carb or low-fat diets — emphasizing foods containing high-quality carbohydrates, plant protein and unsaturated fat — may have a reduced risk of premature death.”
Although low-carbohydrate diets are often used for weight loss and management, and low-fat diets are recommended by some dietary guidelines to help prevent chronic diseases, researchers noted that long-term health associations for both have been inconsistent.
Shan and colleagues conducted a prospective cohort study of participants in the U.S. National Health and Nutrition Examination Survey between 1999 and 2014. Those aged 20 years and older with data available from 24-hour dietary recalls were included in analyses.
Using dietary recalls, they determined scores for overall, healthy and unhealthy low-fat diets and low-carbohydrate diets. Scores were based on the type and total of macronutrients in an individual’s diet.
Among 37,233 adults with a mean age of 49.7 years, 297,768 person-years of follow-up data were available. During that time, there were 4,866 deaths.
Researchers found that overall low-carbohydrate diet and low-fat diet scores were not associated with mortality. However, the quality of the diet affected mortality risk.
With each 20-percentile increase in score, the mortality risk increased by 7% for unhealthy low-carbohydrate diets (adjusted HR = 1.07; 95% CI, 1.02-1.11) and 6% for unhealthy low-fat diets (adjusted HR = 1.06; 95% CI, 1.01-1.12).
With every 20-percentile score increase for healthy low-carbohydrate diet, mortality risk decreased by 9% (adjusted HR = 0.91; 95%CI,0.87-0.95). The same increase in score for healthy low-fat diet was linked to an 11% decrease in mortality risk (adjusted HR = 0.89; 95% CI, 0.85-0.93).
The associations between mortality risk and low-carbohydrate and low-fat diets remained similar in most subgroups after stratification and sensitivity analyses.
When patients express interest in starting these diets, Shan suggested that physicians tell them “no matter which diets they would like to start, more attention should be paid to the quality and food sources of the diets.”
“Generally, a healthy diet should contain high amounts of whole grains, nonstarchy vegetables, whole fruits and nuts, but low amounts of refined grain, red meat and processed meat and added sugar,” he said. – by Erin Michael
Disclosures: Shan reports no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures.