The Mediterranean diet, the DASH diet, and the AHEI diet can all lower the risk of developing type 2 diabetes, according to a new meta-analysis.
The researchers who conducted it analyzed the medical histories of over 800,000 people across 33 studies to arrive at its conclusions.
All three diets share one common principle: reducing the consumption of unhealthy fats, sugars, and processed foods.
According to a new meta-analysis, or study of studies, following any of three healthy diets can reduce the risk of developing type 2 diabetes.
People whose food consumption closely adhered to the eating patterns established in the Mediterranean diet, the DASH diet, and the AHEI diet had lower chances of developing diabetes.
The greatest reduction of diabetes risk, 23%, came for those closely following the DASH diet, followed by the AHEI diet, 21%, and the Mediterranean diet, 17%.
The researchers analyzed the findings of 33 reports describing associations between diet and diabetes, encompassing the medical histories of over 800,000 people.
An important finding of the meta-analysis is that its conclusions applied across a broad range of populations, including African, Asian, European, and Hispanic ethnic groups. This is noteworthy because these groups have different food cultures and different levels of diabetes risk.
One limitation of the analysis is that the decrease in risk, though apparent, did not reach a level of statistical significance for Hispanic people or mixed ethnic groups.
The researchers suggest that this may be due to having less data for these populations in the original studies. They say further investigation, particularly for these populations, is warranted.
The results of the meta-analysis will be presented in September 2025 at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Vienna, Austria. They are yet to appear in a peer-reviewed journal.
What do the Mediterranean, DASH, and AHEI diets have in common?
Perhaps the best-known of the three diets cited in the meta-analysis is the Mediterranean diet. This diet is based on the eating patterns practiced by long-lived people living in the vicinity of the Mediterranean Sea.
It is characterized by an emphasis on unprocessed foods, fruits, vegetables, legumes, whole grains, and lean sources of protein.
The DASH diet, as its full name — Dietary Approaches to Stop Hypertension — suggests, helps a person reduce their intake of sodium and to increase their consumption of magnesium, calcium, and potassium to help maintain a healthy blood pressure. It is in many ways not very different from the Mediterranean diet.
Perhaps the least familiar diet mentioned in the metastudy is Harvard University’s AHEI diet.
Michelle Routhenstein, MS, RD, CDCES, CDN, a preventive cardiology dietitian and heart health expert at Entirely Nourished, not involved in this research, explained what the AHEI diet is:
“The AHEI (Alternative Healthy Eating Index) diet is a research-based scoring system developed to assess diet quality based on how well it aligns with dietary patterns that have been shown to lower chronic disease risk. It encourages high consumption of fiber-dense foods like vegetables, whole fruits excluding juice, whole grains, nuts, legumes; healthy fats like polyunsaturated fats, and lean proteins, specifically fish and poultry. It limits red and processed meats, refined grains, sodium, and sugar-sweetened beverages.”
All three diets share some underlying concepts, said Jason Ng, MD, BA, who teaches endocrinology and metabolism in the Department of Medicine at the University of Pittsburgh.
They all, “contain the common theme of focusing on healthy fats, more plant-based foods like vegetables and fruits, and staying away from processed foods and keeping away from high sugar and added sugars to foods, which are all cornerstones of type 2 diabetes management,” said Ng, who was likewise not involved in this research.
How does diet contribute to diabetes?
The foods people consume are a major driver of diabetes, said Ng. “Type 2 diabetes is caused by increasing insulin resistance.”
“Carbohydrates,” he explained, “especially processed sugars, for example, lead to extra work for the body to process. Over time, potential insulin resistance increases, which forces the pancreas to make more insulin to compensate. When the pancreas cannot make enough insulin to manage blood sugars, you develop [type 2 diabetes].”
Routhenstein noted that some popular foods are particularly likely to cause this to occur, citing sugar-sweetened beverages, refined grains such as white bread and pastries, processed and red meats, and fried and fast foods.
In addition, she said, “diets high in added sugars and sodium but low in fiber-rich whole foods significantly increase diabetes risk by promoting inflammation, impairing insulin sensitivity, contributing to weight gain, and disrupting gut health, all of which play a role in poor glucose regulation.”
Why the DASH diet may decrease diabetes risk the most
“The DASH diet has a slightly higher emphasis on sodium intake that may indirectly worsen insulin resistance,” Ng hypothesized, “so an emphasis on low sodium may indirectly help insulin sensitivity and, thus, improve [type 2 diabetes].”
Routhenstein was drawn to another aspect of the DASH diet, pointing out that it “has the unique offering of honing into certain micronutrients.”
“For example,” she explained, “[the DASH diet] is abundant in both potassium and magnesium that not only supports healthy blood pressure but also plays a key role in glucose metabolism, enhancing insulin sensitivity, facilitating cellular glucose uptake, and reducing systemic inflammation, creating a metabolic environment less prone to diabetes development.”
Will these diets help if you already have diabetes?
Ng suggested it is unclear if these diets can reverse diabetes once it has developed, but suggested it makes sense to give one a try.
He noted that “although reversing [type 2 diabetes] is a complex process, any diet that emphasizes healthy eating, which all of these do, can only help reduce the progression of [type 2 diabetes] and obtain better sugar control and improved insulin sensitivity.”
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