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Experts say a plant-based diet can help control blood sugar levels and other factors that can lead to a type 2 diabetes diagnosis. 10’000 Hours/Getty Images
  • Researchers say women who are overweight can reduce their risk of type 2 diabetes by adopting a Mediterranean style of diet.
  • Experts say the plant-based diet helps control blood sugar levels and other factors that can lead to type 2 diabetes.
  • They note there are ways to swap foods in your diet to adhere to a Mediterranean diet, such as switching from white rice to brown rice.

A Mediterranean-inspired diet can help women who are overweight reduce their risk of type 2 diabetes by up to 30 percent.

That’s according to a study published this month in JAMA Network Open.

Researchers analyzed data from more than 25,000 apparently healthy female healthcare workers from the Women’s Health Study (WHS) at Brigham and Women’s Hospital and Harvard Medical School in Massachusetts.

The WHS is a completed clinical trial that looked at the impacts of vitamin E and low-dose aspirin among initially healthy women free from cardiovascular disease and cancer.

Participants were asked to complete food frequency questionnaires about their dietary intake to develop a baseline between 0 to 9.

The points were assigned for higher intake of Mediterreanean-inclusive foods such as fruits, vegetables, whole grains, legumes, nuts, and fish. It also included moderate intake of alcohol and lower intake of red and processed meat.

Over the span of more than 20 years, the data collection revealed that more than 2,300 of the women had developed type 2 diabetes.

While measuring potential underlying biomarkers such as insulin resistance, lipoprotein metabolism, body mass index (BMI), and inflammation, the study authors said they found no clear cause and effect.

But they did find that such biomarkers are what contributed most to explaining this inverse association between the Mediterrenean diet and diabetes risk.

So what does this mean?

“A lot of the benefit we see can be explained through just a few pathways. And it’s important to note that many of these changes don’t happen right away,” Dr. Samia Mora, an associate professor of medicine at Harvard and an associate physician at Brigham’s divisions of preventive medicine and cardiovascular medicine, said in a news release.

“While metabolism can change over a short period of time, our study indicates that there are longer-term changes happening that may provide protection over decades,” she said.

Experts say the Mediterranean diet is not a fad.

“A Mediterranean diet is greater than just the foods and is really a way of life,” said Caroline West Passerrello, MS, RDN, LDN, CLT, a spokesperson for the Academy of Nutrition and Dietetics.

“In addition to foods common to Spain, Italy, and Greece, it also includes the processes involved in obtaining, cooking, and consuming the foods as well as other lifestyle factors (moderate alcohol consumption, not smoking, being physically active),” she told Healthline.

The Harvard T.H. Chan School of Public Health describes the ideal Mediterranean diet as having an emphasis on healthy fats, limiting animal protein, avoiding smoking, moderating alcohol intake, and increasing regular physical activity.

They say olive oil is recommended as the primary added fat, replacing other oils and fats such as butter and margarine.

Other foods naturally containing healthful fats are highlighted, such as avocados, nuts, and oily fish like salmon and sardines.

When it comes to animal protein, they suggest choosing fish at least twice weekly and other animal proteins such as poultry, eggs, and dairy (cheese or yogurt) in smaller portions either daily or a few times a week.

Red meat is limited to a few times per month.

Finally, Harvard public health officials say we should be choosing water as the main daily beverage, but they add that a moderate intake of wine with meals is permissible.

“This study supports the previous research that shows a diet that focuses on fruits, vegetables, whole grains, and lean proteins can positively influence those biomarkers and reduce the risk for certain chronic health conditions like type 2 diabetes,” Passerrello said.

“These biomarkers, like cholesterol levels and amount of inflammation, can be influenced by diet and lifestyle behaviors,” she added.

However, as the study authors and Passerrello point out, a limitation of this study is that the results are not generalizable.

“The study population consisted of well-educated, female health professionals who were predominantly white. Therefore, these particular findings aren’t necessarily applicable to other ethnicities or men,” Passerrello said.

“Even in the population that was studied, predominantly white females, this study was based on self-reported dietary intake and weights, and the diet was only assessed at baseline,” she added.

Despite the study’s limitations, Andy De Santis, a registered dietitian with a master’s in public health community nutrition, said the health benefits of eating a higher or “greener” Mediterranean diet can likely a wide variety of people.

“Given the robust nutritional benefits that are associated with a ‘green’ Mediterranean dietary pattern, I see no obvious reasons why this style of eating would not be protective across broader portions of the population, although definitive research always helps to increase the confidence in such a claim,” De Santis told Healthline.

“All of my research and education tells me that whole grains, nuts, seeds, fruits, and vegetables represent the most viable avenues to either prevent or manage type 2 diabetes,” he said.

“Within the whole grain/starchy veggie category, emphasizing lower [glycemic index] selections such as sweet potatoes, barley, quinoa, and steel cut oats will certainly be helpful,” he added.

Furthermore, De Santis said everyone can benefit from adding more plant fiber to their dietary pattern.

“There is also a special type of plant fiber, known as psyllium, which is particularly useful at regulating both blood sugar and cholesterol levels,” he said.

“It’s sold in a variety of forms and can be added to yogurt, smoothies, and baked goods to provide a little boost,” he noted.

“The results of this study don’t surprise me in the least because low glycemic index, high soluble fiber foods like fruits, veggies, nuts, seeds, and legumes have long been considered a cornerstone of good blood sugar management,” said De Santis.

“And a dietary pattern which emphasizes them above all else will almost inevitably be protective against the development of type 2 diabetes,” he added.

The glycemic index measures the effect of food on your insulin and blood sugar (blood glucose) levels.

Foods may be grouped into low, moderate, and high glycemic index categories. Higher glycemic foods result in quicker spikes in insulin and blood sugar.

A Harvard Medical School guide demonstrates how to make everyday switches from higher glycemic index foods to lower ones.

The guide recommends these swaps:

  • white rice for brown or converted rice
  • instant oats for steel cut oats
  • corn flakes for bran flakes
  • baked potato for pasta or bulgur
  • white bread for whole grain bread
  • corn for peas or leafy greens

“[Low glycemic index] foods help with blood sugar management largely due to their soluble fiber content,” De Santis said.

“Soluble fiber has a slowing effect on the movement of food through the digestive system and thus leads to a more modest insulin response,” he noted.