It has been known for some time that there is a reduction in the risk of type 2 diabetes for those who follow a Mediterranean diet. However, it has not been clear which factors are key to those beneficial effects.
While a reduction in body mass index (BMI) may be somewhat obvious, other mechanisms include beneficial effects on insulin resistance, lipoprotein metabolism and inflammation.
However, the diet’s antidiabetic effect does not appear to extend to people whose weight is considered healthy (BMI under 25), according to a recent study, which supports the idea that by improving their diet, people can improve their future risk of type 2 diabetes. This is particularly true if they are overweight or obese.
While metabolism can change over a short time on the Mediterranean diet, the study indicates that there are longer term changes happening that may provide protection over decades.
The Mediterranean diet, with an emphasis on healthy olive oil as the predominant source of oil, favours fruits, vegetables, legumes, nuts, and seeds, fish and dairy products, while limiting intake of red and processed meats as well as sweets.
The diet has been linked to as much as a 30% reduction in the risk of diabetes in previous observational studies.
To investigate the precise mechanisms that underlie the prevention of diabetes, the Harvard researchers examined data from 25,317 healthy women participating in the Women’s Health Study who had baseline assessments between September 1992 and May 1995. They started out with an average age of 52.9 years.
Over the course of the study, 2,307 participants developed type 2 diabetes.
After a follow-up averaging almost 20 years, those who had the highest self-reported adherence to the Mediterranean diet (a score of 6 on a scale of 0 to 6) at baseline, had as much as a 30% lower risk of developing type 2 diabetes after some other factor adjustments compared to those with a lower Mediterranean diet score (a score of 3 or less).
The diabetes-related biomarkers that were most closely related to the reduced risk of type 2 diabetes included insulin resistance, accounting for 65% of the reduction, followed by BMI (55.5% reduction), high-density lipoprotein measures (53%), and inflammation (52.5%).
Other factors, though to a lesser degree, included branched-chain amino acids (34.5%), very low-density lipoprotein measures (32.0%), low-density lipoprotein measures (31.0%), blood pressure (29.0%), and apolipoproteins (23.5%).
Differences in glycohemoglobin A1c levels only had a limited effect on the risk (2%).
Further analysis looking at effects of the diet according to baseline BMI showed the reductions in type 2 diabetes associated with higher intake of the Mediterranean diet only extended to those with an above normal weight (BMI ≥ 25) as noted above.
The study was not originally designed to look at the baseline BMI as a factor. But the findings are consistent with the well-known increase in diabetes risk seen with a higher BMI.
Other studies, such as the Nurses’ Health Study, have shown that the risk for type 2 diabetes in women increases with age, even at BMI levels below 25. But the risk goes up exponentially at around a BMI of 25 and higher.
The strong role of insulin resistance was a surprise to the researchers. Since insulin resistance can precede by years and decades the elevated blood sugar and clinical diagnosis of diabetes, it could represent an opportunity to intervene earlier and more intensively by improving insulin resistance through dietary approaches such as the Mediterranean diet.
Another surprise was that glycohemoglobin A1c had no substantial effect on the reduction of diabetes risk with the Mediterranean diet. This could suggest that a rise in glycohemoglobin A1c likely occurs later in type 2 diabetes development.
Like every large population study, there are some limitations in what should be projected from the analysis results. But the findings suggest that more intensively following the Mediterranean diet might have substantial benefits over many years in preventing diabetes, among other health benefits such as lowering insulin resistance and inflammation, improving lipid metabolism, and lowering blood pressure.
Hopefully, more studies will help us understand the relationship. But for now, I would recommend that anyone who is overweight (especially with a family history of diabetes) may want to follow the Mediterranean diet.
https://www.kpcnews.com/article_a9057632-7125-528b-a074-37a34f8fb2c0.html
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