Moderating carbohydrates associated with lower mortality rates in type 2 diabetes

An observational study based on U.S. data compared hazard ratios for death based on overall, unhealthy, and healthy low-carb diet scores according to percentage of energy obtained from total and subtypes of carbohydrate, protein, and fat.

Patients with type 2 diabetes who follow a diet moderately lower in carbohydrates may have lower mortality rates, according to a recent study.

Researchers used data from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2014 to calculate overall, unhealthy, and healthy low-carb diet (LCD) scores according to percentage of energy obtained from total and subtypes of carbohydrate, protein, and fat in patients with type 2 diabetes. Diet intake was assessed using one 24-hour dietary recall in NHANES from 1999 to 2000 and two 24-hour dietary recalls in NHANES from 2001 to 2014. The National Cancer Institute method for estimating usual intake of macronutrients was also used to reduce measurement error.

The overall LCD score ranged from 0 to 30 and was determined by the sum of the three macronutrient component scores. Unhealthy LCD score was determined according to the percentage of energy from high-quality carbohydrates, animal-based protein, and saturated fat, and healthy LCD score was determined according to intake of low-quality carbohydrates, plant-based protein, and unsaturated fat. Patients with higher scores more closely followed a healthy diet.

In isocaloric models, hazard ratios (HRs) were estimated for mortality when energy from total, unhealthy, or healthy carbohydrates was theoretically replaced by equivalent energy from animal or plant-based protein or different types of fat. Deaths were determined by using data from the National Death Index until Dec. 31, 2015. The study results were published April 16 by the Journal of Clinical Endocrinology and Metabolism.

A total of 5,677 patients with type 2 diabetes were included in the study. The mean age was 61.8 years, and 49.7% were women. Overall, 1,432 deaths were documented during a median of 6.3 years of follow-up. After multivariable adjustment that included such factors as lifestyle, diabetes duration, diabetes medication use, and HbA1c level, mortality risk was lowest for patients in the third quartile of overall LCD score (HR, 0.65; 95% CI, 0.50 to 0.85) versus the first quartile. Across quartiles of healthy LCD score, multivariable-adjusted HRs for mortality were 1.00 (reference), 0.78 (95% CI, 0.64 to 0.96), 0.73 (95% CI, 0.58 to 0.91), and 0.74 (95% CI, 0.58 to 0.95) (P=0.01 for trend). Isocaloric replacement of 2% of energy from carbohydrates with plant-based protein or polyunsaturated fatty acids was associated with 23% to approximately 37% lower total mortality, with similar results observed in analyses stratified by age, sex, race/ethnicity, smoking status, body mass index, physical activity, and diabetes duration.

The researchers noted that diet was self-reported and was assessed only at baseline and that type of diabetes could not be definitively determined, among other limitations. They concluded that in this observational study involving a representative sample of U.S. adults, a healthy LCD score was significantly associated with a lower risk of death in patients with type 2 diabetes. This could be because a healthy LCD emphasizes higher intake of plant-based protein and unsaturated fat and lower intake of animal-based foods, which may help create a healthy gut microbiota environment and reduce the dietary acid load, the authors said, although they stressed that more research is needed. “Our findings indicate that adopting a well-balanced, moderate LCD that emphasizes good quality and food sources of macronutrients may aid in preventing premature death among people with [type 2 diabetes],” they wrote.