Our body functions best within a relatively narrow blood glucose range. Unfortunately, it can be challenging for people with diabetes to avoid large fluctuations in blood glucose. 

Chronic hyperglycemia is a primary risk factor for developing diabetes-related complications. However, emerging scientific evidence suggests that glycemic variability may also be problematic. 

Scientists are investigating ways to help minimize glycemic variability. Dietary approaches may help, including adjusting macronutrient proportions to decrease carbohydrate intake. 

Why Glycemic Variability Matters

Glycemic variability refers to significant fluctuations in blood glucose levels over time. These can happen over the course of the day or from day to day. Postprandial blood glucose spikes and periods of hypoglycemia contribute to glycemic variability.

Some degree of glycemic variability occurs, even in people without diabetes. However, glycemic variability is more pronounced in people with diabetes or prediabetes. 

Growing evidence suggests that the size, frequency, and duration of glycemic fluctuations could be a significant factor in the vascular complications of diabetes. These include cardiovascular disease, retinopathy, neuropathy, and nephropathy.

Hyperglycemia may contribute to oxidative stress, inflammation, and endothelial dysfunction. Hypoglycemic events may also trigger inflammation. These are just a few of the ways glycemic variability may increase the risk of blood vessel damage.

Modifying the Diet to Decrease Glycemic Variability

Postprandial hyperglycemia is a major contributor to glycemic variability. Carbohydrate intake can significantly impact post-meal blood glucose. Scientists are investigating how lowering dietary carbohydrate intake may help decrease glycemic variability. 

In a controlled, randomized crossover study, 16 adults with metformin-treated type 2 diabetes were given a reduced-carbohydrate diet or a conventional diabetes diet over a 2-day intervention. The composition of the diets based on the percentage of calories from each macronutrient were as follows:

• Carbohydrate-reduced, high-protein diet: 31% carbohydrate, 29% protein, and 40% fat 

• Conventional diabetes diet: 54% carbohydrate, 16% protein, and 30% fat

The participants wore continuous glucose monitors during the intervention. All measures of glycemic variability showed significant improvements on the carbohydrate-reduced, high-protein diet compared with the conventional diabetes diet. 

Postprandial excursions in blood glucose were reduced by approximately threefold and twofold after breakfast and lunch, respectively, on the carbohydrate-reduced diet compared with the conventional diabetes diet. Also, 24-hour average blood glucose was 16.2 mg per dL lower on the carbohydrate-reduced diet. 

Growing Support for Low-Carb Diet for Diabetes

In recent years, we have witnessed increasing support for low-carbohydrate diets for diabetes, including support among conventional health-care practitioners. In addition, growing scientific evidence affirms that diets reduced in carbohydrates may enhance glycemic control.

A 2019 Diabetes Care consensus report on nutrition therapy for adults with diabetes or prediabetes reviewed different dietary approaches. “Reducing overall carbohydrate intake for individuals with diabetes has demonstrated the most evidence for improving glycemia and may be applied in a variety of eating patterns that meet individual needs and preferences,” the authors concluded. 

By Marsha McCulloch, MS, RDN, LN