March 2022 Issue

Brain Health: Behind the MIND Diet
By Carrie Dennett, MPH, RDN, CD
Today’s Dietitian
Vol. 24, No. 3, P. 12

Plant-Based Nutrition Tailored for Cognitive Health and Alzheimer’s Prevention

When people think of Alzheimer’s disease, they often associate it with loss of memory or the inability to live independently. It’s easy to forget that Alzheimer’s also is the fifth-leading cause of disease-related death in the United States. Currently, 6.2 million people in the United States have Alzheimer’s disease, with someone newly diagnosed every 64 seconds— and those numbers are growing.1

Ayesha Sherzai, MD, a neurologist and codirector of the Brain Health and Alzheimer’s Prevention Program at Loma Linda University in California, called these numbers a “tsunami” when she spoke at the virtual Food & Nutrition Conference & Expo™ in October. She says current numbers may be underestimated because of the false assumption that cognitive impairment and memory problems are a normal part of aging.

“Typically, as we age, we all lose some of our mental sharpness, but that decline is very minimal,” says Christy Tangney, PhD, a professor of clinical nutrition and preventive medicine at Rush University Medical Center in Chicago, who also spoke at the conference. “When we move into mild cognitive impairment, we’re really starting to lose certain capabilities to function in our environment.” As this cognitive impairment gets progressively worse, it can become Alzheimer’s.

While several genes can increase Alzheimer’s risk, Sherzai says adopting habits that reduce or manage cardiovascular risk factors can affect whether these genes become activated. In fact, newer research is pointing to prevention as the new treatment. In 2019, the big news was that lifestyle factors are the best—and only—bet for reducing Alzheimer’s risk at this time.2,3 “For the first time, there was hope,” Sherzai says. “Until then, for decades and decades we were only looking at medication for treatment and management of this devastating disease.”

Sherzai says research is clear that people who have genetic risk of developing Alzheimer’s have a much higher risk if they also adhere to unhealthful lifestyle habits, but that a healthful lifestyle potentially can cut their risk in half. Nutrition is part of that.

Diets for Brain Health
Eating to prevent Alzheimer’s disease and other forms of dementia is a nutrition holy grail. Most research has focused on potential cognitive benefits of the Dietary Approaches to Stop Hypertension (DASH) diet, the Mediterranean diet, and a hybrid of the two, the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet.4

The DASH diet includes an average of seven servings of whole grains, four servings each of fruits and vegetables, and two servings of low-fat dairy foods per day, along with at least four servings of nuts, seeds, and legumes and six servings of lean meat, poultry, and fish per week. It limits sweets to five or fewer servings per week and caps dietary fat at 27% of total calories, saturated fat at 6% of total calories, and sodium at 2,400 mg per day.

The Mediterranean diet also is rich in fruits, vegetables, unprocessed grains, nuts, and seeds, but includes full-fat dairy and recommends four tablespoons of olive oil per day, at least six servings of fish per week, and up to 10 oz of red wine or other alcohol per day.

“There are features of the DASH diet we want to incorporate. There are features of the Mediterranean diet we want to incorporate,” Tangney says about the development of the MIND diet. “But we also want to look at some of the most recent evidence that we see for brain health, which are things that aren’t in either of those diets.”5 This includes incorporating evidence from the Rush Memory and Aging Project (MAP) and Nurses’ Health Study cohort studies, as well as evidence from European animal and cohort studies. In MAP, an observational study of more than 900 community participants aged 58 to 98, participants with diets most closely resembling the MIND diet had cognitive functioning equivalent to someone 7.5 years younger.6

Both the DASH and Mediterranean diets have been shown to reduce the risk of Alzheimer’s disease and other forms of dementia, but only in study participants who have the highest level of adherence. Tangney says that while MAP participants who followed the MIND diet very closely had the best protection from cognitive decline, those who followed the diet “moderately well” still saw some slowing of decline—those in the top tertile had a 57% lower risk of developing Alzheimer’s, while those in the middle tertile had a 35% lower risk. “This is offering great hope for people, because they don’t have to be perfect eaters,” she says.

Dissecting the Differences
What the DASH, Mediterranean, and MIND diets all have in common is that they’re plant-based, which Sherzai says is key. “When you look at the pathological changes that occur in the brain, whether it’s inflammation or oxidation, or abnormalities in glucose metabolism or fat metabolism, a plant-based diet provides all of the raw materials to fight against those processes,” she says, adding that a plant-based diet could be plant-exclusive or include some animal products. “When you look at the MIND diet, the elements that stand out are greens, beans, berries, nuts, and seeds—mostly plant-based. They provide the right kinds of protein, carbohydrates, fiber—which is lacking extensively from our diet—vitamins and minerals.”

However, the MIND diet has a few key differences, including the following, that can create some cognitive dissonance:

• Vegetables. Total recommended servings of vegetables—two per day—is considerably lower than recommended servings for the DASH and the Mediterranean diets. What’s different is the emphasis on green leafy vegetables such as spinach, kale, collard greens, and romaine lettuce. The MIND diet recommends at least one serving per day because observational studies have found green leafy vegetables are a rich source of nutrients, including lutein, folate, beta-carotene, alpha-tocopherol, phylloquinone, and kaempferol, that may have independent mechanisms of action that synergistically protect the brain and slow age-related cognitive decline.7,8

• Fruit. Prospective studies haven’t found an association between fruit as a general category and cognitive decline, so unlike the DASH and Mediterranean diets, the MIND diet doesn’t specify a number of daily fruit servings.6 The only fruit recommendation in the MIND diet is 1/2 cup of berries, two to five times per week. “MIND focuses on berries because berries have been shown to be very effective in cohort studies and animal studies,” Tangney says. This includes positive associations between blueberry and strawberry intake and slower cognitive decline observed in the Nurses’ Health Study.9

• Fish. Given the importance of omega-3 fatty acids from fish for fetal brain development, the fact that the MIND diet sets its recommended minimum fish intake at one serving—compared with six servings for the Mediterranean diet and two servings in the Dietary Guidelines for Americans—is surprising. However, Tangney says, “we only ask them to consume one or more because the evidence isn’t strong for anything other than one or more.”6

• Alcohol. Early versions of the MIND diet recommended one serving per day of wine or other alcohol, but this is no longer emphasized. “If people are already consuming it, that’s fine, but we do not feel comfortable in advising people to drink wine or alcohol,” Tangney says.

Bottom Line
“Genes aren’t destiny when it comes to dementia,” Sherzai says. “Addressing lifestyle and specifically nutrition with our clients, with our patients, and especially those who are at high risk, whether they have a family member with Alzheimer’s disease or have unmanaged vascular risk factors, is critically important.”

— Carrie Dennett, MPH, RDN, CD, is the nutrition columnist for The Seattle Times, owner of Nutrition by Carrie, and author of Healthy for Your Life: A Holistic Guide to Optimal Wellness.

References
1. 2021 Alzheimer’s disease facts and figures. Alzheimers Dement. 2021;17(3):327-406.

2. Weintraub K. Alzheimer’s meeting: lifestyle factors are the best—and only—bet now for reducing dementia risk. Scientific American website. https://www.scientificamerican.com/article/alzheimers-meeting-lifestyle-factors-are-the-best-and-only-bet-now-for-reducing-dementia-risk/. Published July 18, 2019.

3. Dhana K, Evans DA, Rajan KB, Bennett DA, Morris MC. Healthy lifestyle and the risk of Alzheimer dementia: findings from 2 longitudinal studies. Neurology. 2020;95(4):e374-e383.

4. Duplantier SC, Gardner CD. A critical review of the study of neuroprotective diets to reduce cognitive decline. Nutrients. 2021;13(7):2264.

5. Morris MC. Nutrition and risk of dementia: overview and methodological issues. Ann N Y Acad Sci. 2016;1367(1):31-37.

6. Morris MC, Tangney CC, Wang Y, Sacks FM, Bennett DA, Aggarwal NT. MIND diet associated with reduced incidence of Alzheimer's disease. Alzheimers Dement. 2015;11(9):1007-1014.

7. Morris MC, Wang Y, Barnes LL, Bennett DA, Dawson-Hughes B, Booth SL. Nutrients and bioactives in green leafy vegetables and cognitive decline: prospective study. Neurology. 2018;90(3):e214-e222.

8. Holland TM, Agarwal P, Wang Y, et al. Dietary flavonols and risk of Alzheimer dementia. Neurology. 2020;94(16):e1749-e1756.

9. Devore EE, Kang JH, Breteler MMB, Grodstein F. Dietary intakes of berries and flavonoids in relation to cognitive decline. Ann Neurol. 2012;72(1):135-143.