Doctors and researchers know that a person’s diet can have a huge effect on their health and well being. Diet can affect a person’s weight, heart health, and blood pressure. More recently, researchers have found that diet may affect a person’s cognitive outcomes, and may even have the ability to slow cognitive decline.
Previous dietary studies
In past studies, patients were asked to participate in the Mediterranean diet (which is based heavily in plants, olive oil, nuts, and fish) or in a standard low-fat diet. After more than five years, patients who followed the Mediterranean diet were more likely to have better cognitive scores than their fellow low-fat diet participants. In another study, researchers looked at patients who had high blood pressure and were overweight. These patients were started on a DASH (Dietary Approaches to Stop Hypertension) diet or delegated to a regular diet for comparison. After four months, patients on the DASH diet were found to have better psychomotor speed than their regular diet counterparts.
The MIND diet: Does it work?
Researchers at the Rush University Memory and Aging Project looked at a prospective cohort of 923 volunteers from the Chicago area. These patients completed at least two neuropsychological exams through their time on the study, filled out a series of food questionnaires, and all were free of Alzheimer’s disease (AD) at the beginning of the study. These patients were followed from 2004 through the beginning of 2013 and were asked to record their diet for 12 months. Researchers looked at intake of 144 specific food items, including frequencies and portion sizes.
These 144 items fell into either the DASH diet, the Mediterranean diet, or a modified combination of these two called the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet. Like the other two diets, the MIND diet emphasizes plant-based foods and healthy fats, while minimizing animal-based and high saturated fat foods, but the MIND diet goes on to add foods that are linked to protection from dementia such as berries, leafy greens. These foods are all given a score, according to the diet they fall under (DASH, Mediterranean or MIND) and the patient scores were calculated based on the results of the food questionnaires that they filled out.
Results of the MIND diet study
There were 144 cases of AD that occurred among the 923 subjects in this study. Patients who scored the highest on the MIND diet (meaning they followed the diet well) had a 53% reduction in the rates of AD. Even patients who only moderately followed the MIND diet had a 35% reduction in the rates of AD. While patients who followed the Mediterranean diet well also had a significant reduction in the rates of AD, there was no correlation between following the Mediterranean diet moderately and any reduction in AD. There was only a small connection between following the DASH diet and reduction in AD.
Researchers took outside variables into consideration when they scored the effectiveness of the diets. Age, education level, amount of physical activity, behavioral health status, body mass index, current medications, blood pressure, and medical history (such as cardiovascular health, diabetes, and incidence of stroke) were all factors that were taken into consideration and were calculated into how well the diets worked to prevent AD. These were all factors that may have also played a role in AD development or prevention.
Study strengths and limitations
One of the strengths of this study is that the subjects came from a prospective cohort. This means that they were being followed because they are aging and not chosen specifically for this part of the study, limiting a factor known as “selection bias.” They also weren’t filling out food questionnaires or having neuropsychiatric studies for the sole purpose of being on this study. This also can contribute to a lack of bias. The main limitation of this study is that since it is an observational study there is no proof of cause and effect, just suggestion of a correlation. In order to show that the MIND diet definitely protects against AD, there would need to be controlled, randomized scientific studies.
As a point of interest, none of the patients were asked to follow any of the diets specifically. The MIND diet actually was developed independently of this study, as a combination of the DASH and Mediterranean diets. This study was just able to score patients’ current diets and show that the MIND and Mediterranean diets could possibly protect patients against AD.
Morris M, Tangney C, Wang Y, Sacks F, Bennett D, Aggarwal N. MIND diet associated with reduced incidence of Alzheimer's disease. Alzheimer's & Dementia. 2015;11(9):1007-1014. doi:10.1016/j.jalz.2014.11.009