Does the Mediterranean diet lower the incidence of type 2 diabetes among non-Mediterranean populations?

In a recent study published in the Nutrients Journal,  researchers investigated the association between adherence to the Mediterranean diet and the prevalence of type 2 diabetes in Lausanne, Switzerland — a non-Mediterranean population.

Study: Association between Mediterranean Diet and Type 2 Diabetes: Multiple Cross-Sectional Analyses. Image Credit: AntoninaVlasova/Shutterstock.com

Background

Type 2 diabetes, along with obesity, is a growing epidemic worldwide, especially in Western countries, and the prevalence of type 2 diabetes is expected to surpass 500 million by the year 2035.

While genetics and age have a major role in developing type 2 diabetes, physical activity levels and diet are two modifiable risk factors of type 2 diabetes, aiming to prevent type 2 diabetes by lowering the incidence of obesity.

The Mediterranean diet, generally practiced in some countries close to the Mediterranean Sea, including Greece, Lebanon, and Turkey, that cultivate olives significantly reduces the risk of obesity.

This diet comprises a high intake of vegetables, fruits, nuts, legumes, fish, and seafood, alcohol and dairy products consumed in moderation, and a very low intake of red meat.

Given the known benefits of the Mediterranean diet in cardiovascular health and in lowering the risk of neurodegenerative diseases and its positive impact on the climate and sustainability, adherence to the diet has extended beyond Mediterranean regions.

About the study

In the present study, the researchers examined adherence to the Mediterranean diet outside the Mediterranean region in Lausanne, Switzerland. They investigated its impact on lowering the risk of type 2 diabetes.

Given the fact that Switzerland has a very well-developed healthcare system with one of the lowest obesity rates among the Western countries, and the overall population has a high socioeconomic status, the impact of adherence to the Mediterranean diet on the risk of type 2 diabetes can be studied among the Swiss population without major confounding factors.

Data were obtained from a prospective, population-based study assessing the genetic, biological, and clinical factors determining cardiovascular disease risk. The study administered a semi-quantitative food frequency questionnaire and conducted a clinical examination and blood tests.

The food frequency questionnaire assessed the dietary intake and portion sizes of a total of 97 food items that constituted 90% of the carbohydrate, fat, protein, cholesterol, alcohol, retinol, vitamin D, and caloric intake and 85% of the iron, carotene, and fiber content of the diet.

Information from three follow-ups was used to assess the adherence to the Mediterranean diet, and the adherence was calculated using two different methods. One method examined the intake of eight major food types, including vegetables, fruits, cereals, meat, legumes, dairy products, ethanol, and the ratio of monounsaturated to saturated fats.

This method assigned scores based on the consumption of beneficial and detrimental foods. The other method scored the dietary intake similarly but examined the portion sizes of vegetables, fruits, cereals, alcohol, meat, dairy products, and olive oil.

Type 2 diabetes was defined based on fasting plasma glucose levels or the usage of insulin or oral antidiabetic treatments. Information on other covariates such as socioeconomic status, education levels, alcohol consumption, smoking behavior, body measurements, and blood pressure was also gathered.

Fasting plasma glucose and glycated hemoglobin levels were assessed using blood samples.

Results

The results reported that after adjusting for multiple variables, no significant association was found between adherence to the Mediterranean diet and the incidence of type 2 diabetes among the non-Mediterranean population.

The adherence to the Mediterranean diet was found to be high among individuals who had a lower body mass index, had higher education, did not smoke frequently, and had a lower occurrence of hypertension but often consumed alcohol.

The lack of association between adherence to the Mediterranean diet and the incidence of type 2 diabetes did not change based on the level of adherence to the diet either. There were some differences in the adherence patterns between the two methods used to score dietary adherence.

While one method found that the participants who had higher adherence to the Mediterranean diet were mostly women and infrequent alcohol drinkers, the other method found no sex-based differences in the adherence patterns but reported that frequent alcohol drinkers had higher adherence to the Mediterranean diet.

Unlike many other studies that reported an inverse association between the Mediterranean diet and type 2 diabetes, the present study found no correlation between the two factors.

The researchers believe the null finding could be due to inadequate methods of assessing the Mediterranean diet among a non-Mediterranean population.

Since the types of foods consumed within the larger categories of the Mediterranean diet and the food preparation methods can differ in non-Mediterranean countries, the Mediterranean diet scores could have been overestimated in the study.

Conclusions

Overall, the findings reported that among the non-Mediterranean population, adherence to the Mediterranean diet was not correlated to a lower incidence of type 2 diabetes, irrespective of the levels of adherence to the dietary pattern.

These results emphasize the need for more accurate methods of assessing Mediterranean diets among populations outside of the Mediterranean region, considering the differences in food types and preparation methods.

Written by

Dr. Chinta Sidharthan

Chinta Sidharthan is a writer based in Bangalore, India. Her academic background is in evolutionary biology and genetics, and she has extensive experience in scientific research, teaching, science writing, and herpetology. Chinta holds a Ph.D. in evolutionary biology from the Indian Institute of Science and is passionate about science education, writing, animals, wildlife, and conservation. For her doctoral research, she explored the origins and diversification of blindsnakes in India, as a part of which she did extensive fieldwork in the jungles of southern India. She has received the Canadian Governor General’s bronze medal and Bangalore University gold medal for academic excellence and published her research in high-impact journals.