Salad ingredients, including various greens and daikon, in bowls on a tableShare on Pinterest
Certain diets like the MIND diet may have cognitive health benefits. Marta Mauri/Stocksy
  • As a result of aging or age-related disease such as dementia, people may start to experience a slight slowing of processing speed and occasional memory lapses.
  • Diet may offer protective benefits against cognitive decline, but these results have not been repeated in clinical trials.
  • Now, a new study has found that for older people, cutting daily calorie intake by a small amount may improve cognition.
  • Improvements in cognition did not differ significantly between people who followed the MIND diet and those on any mild calorie restriction.

Cognitive change is normal as we age. A slight decline in memory and processing speed may begin as early as your 20s and 30s, although this is usually accompanied by improvements in cumulative knowledge well into old age.

Although no individual nutrients have been found to prevent cognitive decline, observational studies suggest that the Mediterranean diet may have beneficial effects on cognition.

Now, a study has compared the effect of the MIND diet — a hybrid of the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets — and mild caloric restriction on cognition.

The study found that both diets had a small positive effect on cognition, with neither being significantly better than the other.

“These study results point to mild caloric restriction and an average weight loss of 5.5% as lifestyle factors that may support cognition in older adults.”
Molly Rapozo, registered dietitian nutritionist and senior nutrition and health educator at the Pacific Neuroscience Institute in Santa Monica, California

The study is published in The New England Journal of Medicine.

The researchers enrolled a total of 604 people in the study. All participants reported a family history of Alzheimer’s disease and were on suboptimal diets but showed no signs of cognitive decline on testing. All participants had a body mass index (BMI) over 25 (overweight).

They randomly divided the participants into two groups: 301 people were allocated to the MIND diet, and the remaining 303 remained on their normal diet.

In addition, the researchers reduced everyone’s daily intake by 250 calories, as one of the aims of the study was to reduce body mass by 3–5%.

The participants were told to remain on their diet for three years, during which time they had regular dietary counseling over the phone and in person. Both groups were advised about portion size to ensure their calorie intake was correct.

Those on the MIND diet were also told which new foods to include and which foods they should not eat, a key tenet of this eating pattern that is said to help slow cognitive decline.

The researchers followed up with the participants four times during the three years to assess their mental abilities, blood pressure, diet, physical activity, health conditions, and medication use.

After six months, then 12, 24, and 36 months, participants undertook a range of cognition tests run by researchers who were unaware of which diet group they were in. Some also underwent magnetic resonance imaging (MRI) scans to identify any brain changes.

Both showed small improvements in cognitive scores, but there was no significant difference between the two groups at the end of the three years in either cognitive performance or MRI scans.

“The findings are not significant for the MIND diet since the weight loss and cognitive improvements between the MIND diet and just a ‘healthier’ diet were negligible. […] Given the outcome, I suspect the Mediterranean diet would have worked just as well but I’d like to see that trial done next!”
Kate Cohen, a registered dietitian at the Ellison Clinic at Saint John’s, part of the Ellison Institute for Transformative Medicine and Providence Saint John’s Health Center in Santa Monica, CA.

The participants lost, on average, 5kg over the course of the trial, which the researchers suggest may have caused the improvements in cognition.

Previous studies have reported an association between weight loss and improved cognitive function.

Kate Cohen, who was not involved in the study, confirmed this:

“We know that losing weight improves many areas of health including lowering the risk of heart disease, insulin resistance and even some cancers. Studies have also shown that weight loss reduces overall inflammation and that limiting calories is likely to have an anti-inflammatory effect – both of which occurred in this study.”

“While we don’t fully understand the mechanism behind cognitive decline, given all these ways we know weight loss benefits overall health, it feels very unlikely that weight loss wasn’t a factor in this study,” she added.

The researchers also suggest that practice effects may explain the improvement in cognitive tests in the first year for both groups.

Although the researchers expected to see greater improvements in the MIND group than the control group, they suggest that their results may have been affected by the fact that the control group also had a relatively healthy diet. So, perhaps any improvement in diet could benefit cognitive health.

Kate Cohen certainly thinks so:

“The most significant takeaway from this study is that changing one’s diet for the better — even after age 65 — has the potential to prevent cognitive decline in some patients. We know there are lots of other potential health benefits, including improving heart health and preventing chronic disease, so it’s absolutely worth the effort.”

To remain healthy and active even in old age, the Centers for Disease Control and Prevention (CDC) also advises six lifestyle choices that can increase the likelihood of aging healthily:

  • Make healthy diet choices, including fruits, vegetables, whole grains, and lean meats.
  • Keep active and get around 30 minutes of moderate exercise every day.
  • Do not use tobacco.
  • Get regular checkups to prevent disease or detect it early when it is easier to treat.
  • Know your family health history and share it with your doctor so they know what to look out for.
  • Be aware of changes in brain health, particularly changes in memory or brain health.

These measures will not only help maintain physical health but will help keep your brain healthy and functioning, too.