April 5, 2023
More good news on the food and Alzheimer’s front. A new study found that the brains of people who eat a traditional Mediterranean-style diet, rich in foods like leafy greens, fruit, nuts and fish, have far fewer of the typical signs of Alzheimer’s disease. A second study found that those who follow a Mediterranean-type diet reduce their risk of developing Alzheimer’s disease by almost 25 percent.
The first study, from researchers at Rush University Medical Center in Chicago, looked at 581 men and women whose average age was 84 at the start. None of the study participants were known to have Alzheimer’s disease or other forms of dementia while alive. But all agreed to undergo annual clinical evaluations and, after they died, a brain autopsy to look for the telltale amyloid plaques and neurofibrillary (tau) tangles that are a hallmark of Alzheimer’s disease.
Participants also filled out annual questionnaires about their typical dietary habits. The researchers recorded how closely they adhered to one of two heart-healthy diets: a traditional Mediterranean style diet, rich in fruits, vegetables, whole grains, “good” fats like olive oil, and fish; or the MIND diet, a low-salt version of the Mediterranean diet.
To adhere to these styles of diets, a person would need to eat, for example, at least three servings of whole grains, leafy greens and a vegetable daily; have beans every other day or so; eat berries at least twice a week and fish a few times a week; and snack on foods like nuts (in moderation). Foods to be avoided or eaten less often would include red meat, saturated fats like butter and stick margarine, sugary sweets and pastries, whole fat cheese, and fried or fast food. Both the Mediterranean diet and the MIND diet allow for modest amounts of wine (up to one glass a day).
None of the participants had serious memory problems at the start of the study. But by the time they died, an average of seven years later, when most were in their early 90s, 39 percent had received a diagnosis of Alzheimer’s or other forms of dementia. Examination of the participants’ brains after death found that 66 percent met the diagnosis of Alzheimer’s disease, with their brains containing large amounts of the telltale plaques and tangles (even though the correlation is far from perfect, as it is not rare to find people that have plaques and tangles in their brains while alive but do not show memory loss or other symptoms of Alzheimer’s disease).
The researchers found that those people who scored highest for adhering to the Mediterranean or MIND diets had average plaque and tangle amounts in their brains similar to being 12 to 18 years younger than people who did not follow these patterns of eating. When looking at single diet components, researchers found that green leafy vegetables were particularly beneficial for the brain. People who ate seven or more servings of leafy greens per week had plaque amounts in their brains corresponding to being about four years younger than people who ate one or fewer servings per week. The findings were published in Neurology, the medical journal of the American Academy of Neurology.
“Improvement in people’s diets in just one area, such as eating more than six servings of green leafy vegetables per week or not eating fried foods, was associated with fewer amyloid plaques in the brain, similar to being about four years younger,” said study author Puja Agarwal, an assistant professor of internal medicine at Rush. “Our finding is intriguing enough for people to consider adding more of these vegetables to their diet.”
The findings suggest that even simple dietary modifications, such as adding more greens, berries, whole grains, olive oil and fish, may actually delay your onset of Alzheimer’s disease or reduce your risk of dementia when you’re growing old. “While our research doesn’t prove that a healthy diet resulted in fewer brain deposits of amyloid plaques, we know there is a relationship,” Dr. Agarwal said. “Following the MIND and Mediterranean diets may be one way that people can improve their brain health and protect cognition as they age.”
The second report, from researchers in Britain, is one of the largest diet and Alzheimer’s studies to date. It looked at 60,298 men and women who were part of the U.K. Biobank, an ongoing study of health and lifestyle habits in the United Kingdom.
The researchers followed participants for about a decade, including their diets and cognitive health. During that time, 882 had developed Alzheimer’s disease or other forms of dementia. Analysis of the foods they typically consumed revealed that those who ate a Mediterranean-style diet had up to a 23 percent lower risk of Alzheimer’s disease and other forms of dementia than those who did not. The findings were published in the journal BMC Medicine.
The researchers also looked at genetic risk factors that predispose to Alzheimer’s disease, and found that a Mediterranean diet appeared to provide protection against dementia. “The protective effect of this diet against dementia was evident regardless of a person’s genetic risk, and so this is likely to be a beneficial lifestyle choice for people looking to make healthy dietary choices and reduce their risk of dementia,” said study author Janice Ranson of the University of Exeter. “The findings from this large population-based study underscore the long-term brain health benefits of consuming a Mediterranean diet, which is rich in fruits, vegetables, whole grains, and healthy fats.”
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Sources: Puja Agarwal, Sue E. Leurgans. Sonal Agrawal, et al: “Association of Mediterranean-DASH Intervention for Neurodegenerative Delay and Mediterranean Diets With Alzheimer Disease Pathology.” Neurology, March 8, 2023
Oliver M. Shannon, Janice M. Ranson, Sarah Gregory, et al: Mediterranean diet adherence is associated with lower dementia risk, independent of genetic predisposition: findings from the UK Biobank prospective cohort study. BMC Medicine. March 14, 2023