Following a specialized “green” Mediterranean diet may be better than a traditional Mediterranean diet when it comes to metabolic health, including insulin sensitivity, according to a new study published in the Journal of Clinical Endocrinology & Metabolism.
A traditional Mediterranean diet emphasizes abundant fruits and vegetables, as well as moderate amounts of seafood and other lean protein sources, whole grains, beans and other legumes, olive oil, and potentially alcohol centered on red wine. A “green” Mediterranean diet is similar, except that it focuses even more on green vegetables and sometimes on reducing red meat as much as possible. Past studies have shown that a “green” Mediterranean diet may carry unique health benefits — as we wrote earlier this year, one study found that it may help reduce liver fat, a benefit that may be particularly meaningful for many people with diabetes due to the higher incidence of fatty liver disease.
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For the latest study, researchers were interested in looking at fasting ghrelin levels in people who followed different diets. Ghrelin is a hormone that plays a key role in digestive health, and is commonly known as the “hunger hormone” because of the role it plays in activating hunger. That doesn’t mean, though, that less ghrelin is good — in fact, the study authors noted that people with obesity and metabolic syndrome tend to have lower fasting ghrelin levels.
The study had 294 participants with an average body-mass index (BMI, a measure of body weight that takes height into account) of 31.3, which falls in the “obese” category. Men made up the vast majority of study participants at 88%. Initial testing showed that 37% of participants had prediabetes, while 11% had type 2 diabetes.
Participants were randomly assigned, in equal numbers, to follow one of three diets for 18 months — general healthy dietary guidance, a traditional Mediterranean diet, or a “green” Mediterranean diet. They were also instructed to complete a certain amount of physical activity, with each group given the same guidance. Both of the Mediterranean diets had the same relatively low number of calories, and contained 28 grams of walnuts each day. Members of the “green” Mediterranean diet group also consumed 3 to 4 cups of green tea and a special green shake containing the mankai plant each day.
Additional benefits seen with “green” Mediterranean diet
After 18 months, 264 participants remained in the study. The researchers found that both Mediterranean diet groups saw a similar moderate amount of weight loss — an average loss of 2.9% of body weight in the traditional Mediterranean diet group, and 3.9% in the “green” Mediterranean group. But fasting ghrelin levels increased by very different amounts in each of the three groups — by 1.3% in the general healthy diet group, by 5.4% in the traditional Mediterranean diet group, and by 10.5% in the “green” Mediterranean diet group. What’s more, across all three groups, greater fasting ghrelin in men was linked to a beneficial reduction in insulin resistance as well as a reduction in abdominal fat, after adjusting for weight loss. This relationship was not seen in women who took part in the study.
The researchers concluded that particularly among men, following a “green” Mediterranean diet may be an effective way to increase fasting ghrelin levels and reduce insulin resistance and abdominal fat. More research is needed to find out if a similar dietary patterns may result in the same benefits in women, possibly in part by designing a study with a greater number of women as participants.
Want to learn more about the Mediterranean diet? Read “Five Reasons to Try the Mediterranean Diet” and “Eating Patterns and Type 1 Diabetes: Mediterranean Diet,” then watch “What Is the Mediterranean Diet?”