Type 1 Diabetes: New Studies on Vegan and Moderate-Carbohydrate Diets for Type 1 Diabetes

How many carbohydrates should you eat for ideal health with type 1 diabetes? It’s a question that evades an easy answer. With diabetes nutrition, as with most things, one size doesn’t fit all, according to two new studies.

At the “Are We What We Eat?” symposium at the EASD 2023 conference in Hamburg, Germany, two nutrition researchers presented new data that attempted to, if not answer the question of what the ideal diet should be for those with type 1 diabetes, at least suggest ways to expand the conversation to make it more inclusive.

Dr. Hana Kahleova, director of clinical research at the Physicians Committee for Responsible Medicine in Washington D.C., presented findings of a study of a plant-based diet versus a standard portion-controlled diet for those with type 1 diabetes. Since insulin dependence is linked to a decreased life span, she said her aim was to find a way to lower the amount of insulin needed for people with type 1 diabetes through nutrition.

Kahleova cited the Diabetes Control and Complications Trial (DCCT) that documented over 30 years that higher insulin doses in people with type 1 diabetes were associated with a higher body mass index, higher pulse rate, and impaired blood lipids. The consequences have been devastating, she noted, as each increase of 0.1 units/kg/day of insulin dose was associated with a 6% increase in cardiovascular disease.

“Is there anything we can do to address this with nutrition?” Kahleova asked. “Can we actually lower the insulin dose with nutrition?”

The current recommendations for type 1 diabetes are portion control, carbohydrate counting, and minimizing the consumption of processed foods and sugar-sweetened beverages, with the bolus insulin dose calculated based on the carbohydrate content of the meal. Kahleova said thousands of patients reported that different meals with similar carb levels affected them differently, leading to a great deal of confusion and frustration.

“We know that all carbohydrates are not created equal,” she said. “There’s also a lot of variability in terms of fat and protein content and fiber content. The fiber content of the meals seems to be one of the most crucial aspects for people with type 1 diabetes.”

The average American consumes 16 grams of fiber a day, only half the recommended daily amount. The average in Europe is a bit higher with about 20 grams a day, but still not close to enough. Another study has shown that 30-35 grams of fiber a day was associated with a reduction in all-cause mortality by about 15% compared with low-fiber intake.

“Fiber in diabetes has a much more important role to people than for the general population,” Kahleova said, adding that for those with diabetes, both type 1 and type 2, the all-cause mortality from fiber deficiency might be as much as 45%, and 39% for cardiovascular disease.

“We know that a plant-based diet has been shown to be beneficial in type 2 diabetes, improving insulin sensitivity as well as improving beta cell function in overweight people with no diabetes,” she said, adding she was curious if the same benefits were possible for those with type 1.

Kahleova said this small study, consisting of 58 people with type 1 diabetes, was the first plant-based diet trial looking at insulin resistance for people with type 1 diabetes, adding that more work now needs to be done to follow up on the encouraging results.

The study found:

• Energy intake did not change significantly in either group from the start to the end of the trial period. In the vegan group, the carbohydrate intake increased from about 200 g to 300 g a day, while the fat content went down to keep the calories consistent. In the portion-controlled group, the macronutrient ratio stayed steady.
• Total daily insulin dose did not change in the portion-control group, but it did decrease significantly, by 12.1 units a day, or a 28% drop, in the vegan group.
• Insulin sensitivity did not change significantly in the portion-control group, but it increased in the vegan group by 144%.
• A1C deceased in both groups. It decreased by 0.6% in the portion-control group and by 0.8% in the vegan group.
• Body weight didn’t change in the portion-control group, but it did decrease by 11.5 pounds on the vegan diet.
• Total cholesterol dropped significantly on both diets, but it decreased more on the vegan diet. LDL cholesterol levels were reduced only on the vegan diet.
• Kidney function improved on the vegan diet over the portion-control diet.

“This is a novel approach for people with type 1 diabetes,” she told diaTribe about the study. “At first, it may seem intimidating to eat so many carbohydrates, but the most important aspect is that when people want to try this diet, they need to keep the fat content low. You need to pick which will be your main fuel.”

Sofia Sterner Isaksson, of the University of Gothenburg, Sweden, presented a different study looking at varying carbohydrate ratios in diets for type 1 diabetes to evaluate the effects of carbohydrate intake on glucose control. Her team compared a moderate-level carbohydrate diet (in which 30% of the day’s energy came from carbohydrates) with a traditional diet (in which half of the day’s calories came from carbohydrates).

The small study, looking at 50 people with type 1 diabetes, found that those on the moderate carbohydrate diet had better glucose control. The group on the moderate carbohydrate diet also had a better average time in range, by 5%, and less time above range, by 6.4%. Also notable, she said, was a reported higher treatment satisfaction rate for the moderate group. There was no increased risk for hypoglycemia, dyslipidemia, ketoacidosis or elevated blood pressure between the two diet groups.

“These results indicate that a moderate carbohydrate diet can be an effective and safe diet option for some people with type 1 diabetes,” Sterner Isaksson said. “Both diets were individualized by a dietitian and were healthy, and this was important so as not to negatively impact other health markers like weight, blood pressure or lipids.”

Reflecting on the data presented earlier by Kahleova, Sterner Isaksson told diaTribe after the panel discussion that it was clear that there was more than one way for people with type 1 diabetes to eat in ways that supported their health and diets should be individualized.

“It’s important to have different types of diets that fit with different individuals,” she said. “Lowering the amount of carbohydrates could fit for some people, but a plant-based diet with higher carbohydrate content with a lot of fibers could work better for others. That is why it’s so nice to see new studies investigating diets in type 1 diabetes.“