Editor’s note: Tune in to CNN’s Eat, But Better: Mediterranean Style. Our eight-part guide shows you the expert-backed, delicious eating lifestyle that will boost your health for life.
The results are from the prospective clinical trial of the Mediterranean diet, a dietary intervention to delay neurodegeneration, or the MIND diet—a diet specifically designed to boost the brain—and they’re less stellar than expected.
“We really expected the MIND diet to show a higher effect than the control group, so we were quite surprised by the result,” said lead study author Lisa Barnes, associate director of the Alzheimer’s Disease Research Center at Rush University Medical Center in Chicago.
In fact, the MIND Diet improved the brains of those who followed it for three years. At the end of the study, magnetic resonance imaging (MRI) showed fewer white matter hyperdensities (small lesions) and a larger volume of both gray matter (the brain’s cognitive center) and white matter (the brain’s communication highway).
But here’s the catch – the brains of the control group who didn’t eat the MIND diet improved to a similar degree.
Previous studies have shown that both the MIND diet and the Mediterranean diet significantly reduce the risk of cognitive decline and Alzheimer’s disease. However, Barnes said many studies have taken much longer.
Leading nutrition researcher Dr. Walter Willett, professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health and professor of medicine at Harvard Medical School, said.
Willett pointed to an old clinical trial that found that eating more beta-carotenoids, antioxidants found in red, yellow, orange and dark green fruits and vegetables, produced cognitive benefits — but only after years of following the diet.
“After 15 or more years of beta-carotene supplementation, there was significantly better cognitive and task function in the beta-carotene group compared to placebo, but after only several years there was no difference,” said Willett, who was not involved in the new study. Stady.
In addition, people in the control group in the new study may have improved their diet rather than sticking to eating instructions as they always had, said Barnes, who is presenting her paper Tuesday at the 2023 International Alzheimer’s Conference in Amsterdam.
“It’s not as if the people who were on the control diet stayed flat,” she said. “Everyone was eating healthy, losing weight, and so they all got better. The takeaway is that regardless of type, a healthy diet seems to improve cognitive function.”
said Dr. David Katz, a preventive and lifestyle medicine specialist who founded the nonprofit True Health Initiative, a global coalition of evidence-based lifestyle medicine experts. He did not participate in the study.
“It is possible that enrollment in the study will raise awareness of prudent nutritional practices to protect cognition in people who are already interested in this,” Katz said. “This study did not rule out difference. It simply failed to confirm one.”
Developed in 2015 by researchers at Rush University in Chicago, the MIND diet incorporates much of a plant-based Mediterranean diet, which focuses on fruits, vegetables, whole grains, beans, seeds, nuts, and plenty of extra-virgin olive oil. Red meat and sweets are rarely eaten, but fish, full of good-for-you omega-3 fatty acids, is a staple.
The MIND diet also accommodates elements of the Dietary Approaches to Stop Hypertension (or DASH) diet. The DASH diet focuses on lowering blood pressure and cholesterol, which can lead to heart attacks and strokes, and constriction of small blood vessels that can lead to dementia. The standard DASH diet limits salt to 2,300 milligrams per day, which is less than a teaspoon of table salt.
Despite the disappointing results of this trial, other studies have found that the MIND diet can reduce the risk of cognitive decline and Alzheimer’s disease.
Several studies have found that the Mediterranean diet can reduce the risk of diabetes, high cholesterol, dementia, memory loss, depression, and breast cancer. This diet, which is more of an eating style than a restrictive diet, has also been linked to stronger bones, a healthier heart, and a longer life. The DASH diet has been shown to lower blood pressure and is the American Heart Association’s best diet.
The MIND Diet takes the Mediterranean and DASH diets to the next level by focusing on foods known to boost brain health. Dark leafy greens should be eaten every day of the week on the MIND diet. These include watercress, cabbage, dandelion greens, endive, grape leaves, kale, mustard greens, romaine lettuce, spinach, Swiss chard, and turnip greens.
Berries are also emphasized more than other fruits in the MIND Diet. Blackberries, blueberries, cranberries, or strawberries should be eaten at least five days a week.
In addition, you should eat three servings of whole grains daily. You should eat beans for four meals a week, poultry for two meals, and fish at least once a week. Eat nuts five times a week, and avoid butter, cheese, red meat, fried foods, pastries, and desserts.
A 2017 study of nearly 6,000 healthy older Americans with an average age of 68 found that those who followed a Mediterranean diet or the MIND diet reduced their risk of dementia by one-third.
The study, published Tuesday in the New England Journal of Medicine, followed 604 overweight people over 65 for three years. All had a first-degree relative with Alzheimer’s disease and were cognitively normal at the start of the study.
The experimental group was asked to follow the MIND diet while cutting 250 calories per day with the help of a counsellor. Vitamin supplements are not permitted. This group was supplied with adequate amounts of olive oil, berries and nuts every month.
The control group was told to continue eating their usual diet without vitamins but also to try to cut down by 250 calories a day with the help of counseling. They were given $30 gift cards a month.
A battery of cognitive tests was administered when the study began and repeated at set intervals, while regular blood tests measure biomarkers, such as beta-carotene, that indicate how well each person follows the MIND diet.
When diet quality was reached at the start of the study, both groups were equal. However, by the end of six months, people on the MIND diet had improved their diet quality score by more than three points — which had been maintained for three years — while the control group had improved by less than one point. By the end of the study, people in both groups had lost five kilograms, or 11 pounds.
“The five-kilogram weight loss in both groups is impressive, better than many weight loss trials,” Willett said. “It’s clear that the control group was making dietary changes.”
Blood tests found that levels of carotenoids, such as beta-carotene, were significantly higher initially in the group on the MIND diet, but that the increase “did not persist over time, and in most trials was real but modest,” Willett said.
Vegetables and fruits are the main sources of carotenoids, Willett said, “and they also seem to be the most important component of the Mediterranean diet for cognitive function.” “The experiment introduced olive oil and nuts, but not vegetables, so it should come as no surprise that differences in carotenoids were not preserved.”
Experts say that such results, while disappointing, do not mean that the mountains of research on the benefits of the Mediterranean diet and DASH have been disproved. Rather the opposite is true.
Katz refers to the “blue zones,” which are areas of the world where people typically live long, healthy lives to the age of 100 and over. “All Blue Zone residents have very low rates of dementia up to age 100, but they have widely varied diets,” said Katz, who has published research on how food can be used as a preventive medicine.
“We have ample reason to suspect that more than one high-quality diet, not just MIND, will provide a similar benefit.”