Highly Touted Plant Based MIND Diet Disappoints in Clinical Trial - Cognitive Benefits Questioned
The Alzheimer’s Hub of Hope has four sections: Heroes, Highlights, Headlines and Helpers/Caregivers. This post is aligned to the headlines section.
Summary
A three year random controlled clinical trail published in the July 18, 2023 New England Journal of Medicine shows no improvement in cognation or brain scans between the group eating the primarily plant based MIND diet and the control group which ate their normal diets.
As described below, the MIND diet was develop by experts, using survey data, to improve the health of the aging brain and is highly touted by the medical community. The article can be found here.
What is the MIND Diet?
The MIND diet (Mediterranean-DASH Diet Intervention for Neurodegenerative Delay) was developed by a research team at the Rush University Medical Center and the Harvard Chan School of Public Health and targets the health of the aging brain. It combines attributes of the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets.
The research team followed a group of older adults for up to 10 years from the Rush Memory and Aging Project (MAP), a study of residents free of dementia at the time of enrollment. They were recruited from more than 40 retirement communities and senior public housing units in the Chicago area. More than 1,000 participants filled out annual dietary questionnaires for nine years and had two cognitive assessments. A MIND diet score was developed to identify foods and nutrients, along with daily serving sizes, related to protection against dementia and cognitive decline. The results of the study produced fifteen dietary components that were classified as either “brain healthy” or as unhealthy. Participants with the highest MIND diet scores had a significantly slower rate of cognitive decline compared with those with the lowest scores. The effects of the MIND diet on cognition showed greater effects than either the Mediterranean or the DASH diet alone.1
The results of the research was published in 2015 and the diet has been embraced by experts such as Dr. David Katz, director of the Yale University Prevention Research Center, Dr. Walter Willett, chair of the Department of Nutrition at Harvard University and Dr. Lisa Young, author of "The MIND Diet: A Scientifically Proven Way to Prevent Alzheimer's Disease". A quick search of Amazon identified over 30 books with MIND Diet in their title. It really is a highly touted and popular tool thought to slow down cognitive decline.
The healthy items the MIND diet include:
3+ servings a day of whole grains
1+ servings a day of vegetables (other than green leafy)
6+ servings a week of green leafy vegetables
5+ servings a week of nuts
4+ meals a week of beans
2+ servings a week of berries
2+ meals a week of poultry
1+ meals a week of fish
Mainly olive oil if added fat is used
The unhealthy items, which are higher in saturated and trans fat, include:
Less than 5 servings a week of pastries and sweets
Less than 4 servings a week of red meat (including beef, pork, lamb, and products made from these meats)
Less than one serving a week of cheese and fried foods
Less than 1 tablespoon a day of butter/stick margarine
Essentially the diet recommends a lot of whole grains, vegetables and other plant foods such as nuts and beans while minimizing saturated fat like red meat, butter and cheese.
Why was a Clinical Trial Needed?
The highly touted MIND diet is based on what initially appears to be a very thorough, structured process conducted by top notch institutions. The study, published in 2015, lasted ten years with over 1,000 participants. It certainly sounds like the results should be valid. However, all of the data was collected via annual dietary surveys which is classified as an observational study and is considered lower on the hierarchy of evidence2. (I’m pretty sure I wouldn’t be able to accurately document my food consumption in an annual survey).
Note: RCT stands for randomized control trial.
The Evidence Hierarchy
Observational studies, do not allow researchers to make predictions or establish causality but only to look at correlations, however; these studies provide the impetus needed to fund more expensive experimental studies that provides better evidence. So the clinical Trial of the MIND Diet for Prevention of Cognitive Decline in Older Persons3 was initiated.
The Clinical Trial and Its Disappointing Results
The below quote from the clinical trial’s abstract, as I interpret it, was to prove or disprove the conclusion from observational trial research that showed the positive outcomes of the MIND diet using a stronger and more valid clinical methodology.
“Findings from observational studies suggest that dietary patterns may offer protective benefits against cognitive decline, but data from clinical trials are limited. The MIND diet, is a hybrid of the Mediterranean diet and the DASH diet, with modifications to include foods that have been putatively associated with a decreased risk of dementia.”
The clinical study was a three year randomized control trial which created two groups of approximately 300 people each. Participants completed cognitive assessments and magnetic resonance imaging (brain scan looking for plaque) at the beginning of the study to create a baseline for post trial comparison.
One group was assigned to eat the MIND diet and the other group ate normally. The MIND diet group was provided “healthy MIND food” such as vegetables, seeds and nuts and the control group was given a gift card to buy food. There was counseling to improve adherence to the assigned diet. After three years the participants completed the same cognitive assessments and brain scans. The results and conclusion of the study are:
At the trial's conclusion, there were no between-group differences in change in white-matter hyperintensities, hippocampal volumes, and total gray- and white-matter volumes on MRI (brain scan).
Among cognitively unimpaired participants with a family history of dementia, changes in cognition and brain MRI outcomes from baseline to year 3 did not differ significantly between those who followed the MIND diet and those who followed the control diet with mild caloric restriction.
The study’s lead author, Lisa Barnes, associate director of the Alzheimer’s Disease Research Center at Rush University Medical Center in Chicago is quoted below.
“We really expected that the MIND diet would show an effect above the control group, so we were quite surprised by the outcome”
Apparently she expected the study to prove the benefits of the MIND diet but they disproved them.
My Thoughts
I was really surprised that such a highly embraced, supported and recommended diet (or any health / medical advice) could be based on such flimsy evidence that produced the MIND diet. Essentially, annual surveys to older people in retirement and public housing communities. Ask yourself how many servings of whole grains, beans or anything else you ate in the previous twelve months. How accurate do you think you’d be?
As an auditor / risk professional for almost 40 years I would never base a conclusion on survey or interview evidence.
Kudos to the Rush University Medical Center for initiating this “better evidence” study and for being unbiased in its results even though they were clearly surprised. The Rush University Medical Center was instrumental in creating the MIND diet in 2015 so it had to be disappointing to nullify this previous research.
Many Alzheimers experts believe that the disease is caused by many factors besides diet. Stress, exercise and sleep come to mind. So the disappointing results of the clinical trial may be impacted by being too narrow in their approach and not considering these other factors.
If you are following the MIND diet only for its perceived cognitive improvement and not because you enjoy it or desire some other benefit you may want to reconsider it based on the new data.