Can a low-carb diet provide long-term benefits for T1D?

Belinda Lennerz, MD, PhD

Very low-carbohydrate diets-once the only hope for Type 1 diabetics-may hold the key to improving long-term self-management of the disease, according to a new study. The report, published in Pediatrics, reveals that although there is no general recommendation for carbohydrate restrictions in patients with Type 1 diabetes (T1D) currently, it might be worth taking another look at this old-school solution.¹

According to the study, severe carbohydrate restriction was one of the only ways to extend the life of a child with diabetes before the discovery of insulin. After insulin was discovered, carbohydrate restrictions were relaxed, and now the American Diabetes Association recommends individualized diets rather than diets based on macronutrients of blanket carbohydrate restrictions.

This report, however, investigated the effects of a diet that contained 5- to 8-times fewer carbohydrates than the typical diet. The diet followed by study participants included a weight-based carbohydrate plan of 30 grams per day from fibrous vegetables and nuts with a low glycemic index, according to the researchers. Carbohydrates previously consumed were replaced by high-protein foods, and insulin dosages were adjusted as needed.

The goal of the study was to evaluate the impact of very low-carbohydrate diets on individuals with T1D. The investigators assessed 316 individuals who were following a very low-carbohydrate diet as recommended in the book Dr. Bernstein’s Diabetes Solution: The Complete Guide to Achieving Normal Blood Sugars. Participants included both adult patients who had T1D as children, and children with diabetes whose parents completed the online survey through which the study was conducted. Researchers also reviewed the medical records and sent surveys to physicians of participants who gave permission for this.

Survey data included current hemoglobin (Hb) A1C levels and any changes after the switch to a very low-carbohydrate diet; total daily insulin doses; and reports of adverse events. The mean daily carbohydrate intake of participants was 36 grams, and a mean HbA1C of 5.67% was reported, according to the study data. On average, participants had followed very low-carbohydrate diets for 2 to 4 years, and only 7 participants reported diabetes-related hospitalization in the year before the study. 

The research team notes that despite advances in medical care, management of T1D remains suboptimal, and overall average HbA1C levels in Type 1 diabetics is 8.2%, with just 20% of children and 30% of adults with the disease achieving their glycemic targets.

Participants who followed the very low-carb diet plan reported near-normal glycemic control, plus low rates of hypoglycemia and other adverse events. They were generally happy with their health and diabetes control, according to the report.

"These findings are without precedent among people with T1DM, revealing a novel approach to the prevention of long-term diabetes complications," the research team notes.

The study documented other positive impacts of the diet, including improved cardiovascular health measures. Children tolerated the diet plan as well as adults, the report points out, which researchers called "promising" in light of the adverse effects poor glycemic control has on brain development and growth.

Belinda Lennerz, MD, PhD, an instructor in Pediatrics at Boston Children's Hospital, Massachusetts, and lead author of the study, says it reveals that very low-carbohydrate intake may hold the key to improving long-term self-management of T1D.

"Our study shows normal blood glucose values, low rates of acute diabetes complications, and normal height and weight in a large group of adults and children with Type 1 diabetes mellitus who were using a very low-carbohydrate diet," Lennerz says. "This is a level of metabolic control that is generally not thought to be achievable for persons with Type 1 diabetes mellitus. The findings should open the dialog on carbohydrate modification for diabetes management."

According to Lennerz, there are concerns by some experts about the safety of this diet, but she says the results of this study show that it's an option that is worth a deeper look.

References:

1. Lennerz BS, Barton A, Bernstein RK, et al. Management of Type 1 diabetes with a very low-carbohydrate diet. Pediatrics. 2018;141(6):e20173349.