Dietary advice for individuals with type 2 diabetes (T2D) is mainly grounded in common sense: Clinicians advise patients to eat in a way that controls their blood sugar, manages their weight, and makes them feel well.

But patients might express curiosity about whether specific diets could help them manage their diabetes. Although research is limited, recent studies support diabetes-specific benefits of several popular diets, particularly the Mediterranean and dietary approaches to stop hypertension (DASH) diets.

Here’s a look at research findings for four common diets that patients with diabetes may encounter.

The DASH Approach

DASH is rich in fruits, vegetables, whole grains, and low-fat dairy products, and it limits foods that are high in saturated fat and sugar.

While this well-established diet is known to lower blood pressure, it’s sometimes recommended to adults with diabetes, Elizabeth Selvin, PhD, MPH, an epidemiologist at Johns Hopkins University, Baltimore, told Medscape Medical News. Because research was lacking on its benefit for patients with diabetes, she and colleagues conducted a randomized crossover feeding trial to investigate the diet’s impact on glucose control.

The study, published in Nature Medicine, involved 89 adults with T2D who were fed four diets each lasting 5 weeks with a break of at least 1 week between them. The diets, all 2000 kcal, were two DASH-style diets adjusted for diabetes (DASH4D), one with higher sodium (3700 mg/d) and the other with lower sodium (1500 mg/d), and two comparison “typical American” diets, one with higher sodium and one with lower sodium.

To facilitate diabetes management, the carbohydrate target was lower and the targets for potassium and unsaturated fat were higher in the DASH4D diets than in the original DASH.

The researchers measured DASH4D’s effects on mean glucose levels and the percentage of time spent with glucose between 70 and 180 mg/dL (time in range).

“We found that when participants consumed the DASH4D diet, they had a clinically meaningful reduction of average blood glucose level and an increase in average time in range compared to when they consumed a standard diet,” Selvin said.

Participants eating the DASH4D diets had blood sugar levels that were on average 11 mg/dL lower than when eating the standard diet, and they stayed in the optimal blood glucose range for an extra 75 min/d, she noted.

“Both these effects are considered clinically meaningful for people with diabetes, as they may lower risks of heart disease, kidney disease, and other long-term adverse consequences of diabetes,” Selvin said. “We hope that the results will lead to incorporating the DASH4D diet into clinical guidelines and improve type 2 diabetes management in the population,” she said.

Mediterranean Diet

The Mediterranean diet typically includes plenty of vegetables and fruits, legumes, nuts and seeds, and cereals; relies on extra-virgin olive oil as the main fat; and involves low consumption of red meat and moderate consumption of dairy products and fish, poultry, and eggs.

A literature review of clinical trials and prospective cohort studies involving more than 100,000 individuals found that the Mediterranean diet reduced T2D risk and improved blood sugar control in people with the disease. Studies found that high levels of adherence to the Mediterranean diet reduced diabetes risk by about 20%, wrote Sandra Martín-Peláez, MD, of the University of Grenada, Granada, Spain, and colleagues in the review, published in Nutrients.

The researchers also highlighted a 2015 meta-analysis from the European Journal of Clinical Nutrition in which Mediterranean-style diets were associated with significantly greater reductions in A1c, fasting plasma glucose, fasting insulin, BMI, and body weight than control diets among individuals with T2D. Those following a Mediterranean diet showed improvements in cholesterol, triglycerides, and blood pressure compared with control individuals.

“The success of the Mediterranean diet in reducing A1c values is clear; nevertheless, the degree to which it is compared depends on the diet,” the researchers wrote.

The Mediterranean diet has been shown to decrease A1c levels compared with a control, such as a low-fat or low-carbohydrate diet, they noted. While vegan and low glycemic index diets also improve A1c levels, the studies involved had small sample sizes, so more research is needed, they added.

Paleolithic (Paleo) Diet

The Paleo diet emphasizes lower carbohydrate intake and consists of whole, unprocessed foods presumably eaten by early humans, such as fruits, vegetables, lean meats, and fish.

Although limited evidence suggests the Paleo diet offers some benefits for weight management, glucose control, and lipids in T2D, long-term adherence and safety remain unclear because of the diet’s restrictions, noted a 2024 review published in Human Nutrition & Metabolism. The few small, short-term studies on the topic are inadequate to properly evaluate the effectiveness of Paleo diets on T2D, and larger, high-quality randomized controlled trials with longer follow-up periods are needed, it concluded.

Ketogenic (Keto) Diet

Research on low-carb diets for diabetes is limited, but a study published in The American Journal of Clinical Nutrition in 2023 compared the effects of a keto diet and a Mediterranean diet on hemoglobin in individuals with prediabetes and T2D.

In the study, Christopher D. Gardner, PhD, a professor at Stanford University, Stanford, California, and colleagues randomly assigned 40 adults to a well-formulated keto diet (carbohydrates, 20-50 g/d; proteins, ∼ 1.5 g/kg ideal body weight/d; remaining calories from fat) or a Mediterranean diet with the additional restriction of avoiding added sugars and refined grains. Both diets lasted 12 weeks with no washout period between them.

The A1c values were not significantly different between the diets at 12 weeks. The keto diet was associated with a greater decrease in triglycerides, but it also was linked with elevated low-density lipoprotein (LDL) cholesterol and lower nutrient intakes.

The significant finding of an adverse higher LDL cholesterol level in patients in the keto group made sense because those patients were eating more saturated fat and less fiber than patients in the Mediterranean diet group, Gardner told Medscape Medical News. The beneficial reduction in triglycerides in the keto group also made sense because low-carb and high-fat diets tend to lower blood triglycerides, he added.

However, Gardner said, “I think the keto diet is overly restrictive and hard to sustain for most people.”

Importance of Individualization

Dietary plans for individuals with diabetes must be constructed in a way that balances many factors, said Andrew Kraftson, MD, a specialist in endocrinology and internal medicine at the University of Michigan, Ann Arbor, Michigan, told Medscape Medical News.

A comprehensive medical assessment should be conducted prior to any dietary recommendations for patients with diabetes to identify factors that would affect diet selection, said Kraftson, who was not involved in the studies mentioned. For example, if a patient with diabetes also has chronic kidney disease, their kidney team may request that protein intake be limited to a certain maximum amount, he explained.

Additionally, individuals on insulin may need preemptive and ongoing dose adjustments to accompany dietary changes, he said.

“Not only does the diet need to match the medical issues, it must also be mindful of cost, convenience, resource availability, time constraints, food preparation knowledge/skills, and taste preferences,” Kraftson added. Other considerations when assessing diabetes diets include learned behavior, environmental challenges, mental health concerns, and both metabolic and hedonic stimuli for eating, he noted.

Education about carbohydrates is a primary goal for individuals with diabetes, Kraftson said.

The American Diabetes Association recommends that people with T2D select carbohydrates that are nutrient-dense — those that are rich in fiber, vitamins and minerals, and low in added sugars, sodium, and unhealthy fats. People with the condition should eat smaller amounts of beans, lentils, and minimally processed starchy carbohydrates and avoid processed carbohydrates and those with added sugar.

The evidence supporting various types of diets is limited because such studies are challenging to design and execute, Kraftson noted. “Depending on the literature reviewed, there can be compelling reasons to try any of these diets in a way that best matches the individual patient. We know that a patient’s ability to adopt, adapt, and sustain a diet may be the most important factors to see health progress.”

If a patient expresses an interest or preference for a particular dietary strategy, Kraftson encourages them to try it.

“For those needing a better foundation of dietary knowledge, more guidance with problem-solving, or those who struggling despite various efforts, I recommend that we utilize our dietitian colleagues to develop a comprehensive needs assessment and provide guidance to match with a dietary plan,” he said. “For those needing more intensive treatment of both diabetes and weight, I consider a comprehensive program that incorporates meal replacement therapy.”

The US food system is loaded with products with added sugars and refined grains, “which are the two factors that are most problematic for individuals with diabetes,” Gardner said. “Regardless of what diet you are trying to follow, it can be challenging when those high-sugar/high refined-carb foods are ubiquitous.”

The food environment has to change so that individuals who are trying to make healthier choices have plenty of options for doing so, Gardner said. Making healthy food the easiest option will take effort on the part of the food industry, including retailers and institutions, such as hospitals, schools, and the military, that provide food, he said.

Funding for each of the studies is listed in the original publication.

Selvin, Kraftson, and Gardner had no financial conflicts to disclose.