Food for thought: Diet linked to reduction of Alzheimer’s disease-related biomarkers

10 Mar 2023 --- Neuroimaging has revealed a positive association between adherence to the MIND and Mediterranean diets and the reduction of tau tangles and amyloid plaques in the brain – the key signatures of Alzheimer’s disease.

The two eating strategies are similar, yet stress different eating patterns. The Mediterranean diet recommends three or more servings of fish per week, with whole grain cereals, legumes, olive oil, potatoes, vegetables and fruit making up the rest.

The MIND diet is a hybrid of the Mediterranean and DASH (dietary approaches to stop hypertension) diets that prioritizes green leafy vegetables like spinach, kale and collard greens along with other vegetables. Furthermore, it prescribes the consumption of berries instead of fruit and only recommends one or more servings of fish per week. 

Both diets recommend avoiding red meat and high-fat dairy. They also both allow for small amounts of wine.The study associated adherence to the diets to brain biomarkers similar to that of someone up to 18 years younger.

“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,” explains Dr. Puja Agarwal, lead author of the study and professor at RUSH University in Chicago, US.

 “While our research doesn’t prove that a healthy diet resulted in fewer brain deposits of amyloid plaques, also known as an indicator of Alzheimer’s disease, we know there is a relationship and following the MIND and Mediterranean diets may be one way that people can improve their brain health and protect cognition as they age.”

Gaging the extent
The study, published in Neurology, included 581 people who had agreed to donate their brains at death to advance dementia research. The participants, whose average age was 84,  completed annual questionnaires asking how much they ate of food items in various categories.

All of the participants died an average of seven years after the start of the study, and 66% met the criteria for Alzheimer’s disease at the time of their passing. Researchers then examined their brains with neuroimaging to determine the amounts of amyloid plaques and tau tangles present at the time of death. 

According to the National Institutes of Health, amyloid plaques are aggregates of misfolded proteins that form in the spaces between nerve cells in the brain. Tau tangles are abnormal accumulations of the tau protein called tau that forms twisted fibers, or tangles, inside the brain’s nerve cells.

These tangles can then interfere with the normal functioning of the brain’s neurons and may eventually lead to neuronal death.

Adherence the keyThose who consumed the largest amount of leafy greens also had the “youngest” brains.
The study awarded different scores related to how well the participants adhered to each diet. For the Mediterranean diet, participants were given a score of zero to 55. For the MIND diet, participants were given a score of zero to 15. 

One point each was given for consuming brain-healthy food groups, including green leafy vegetables, other vegetables, nuts, berries, beans, whole grains, fish, poultry, olive oil, moderate amounts of wine and coffee.

Both groups lost points if they consumed more than the recommended amount of foods in the five “unhealthy” food groups, including red meats, butter and margarine, cheese, pastries and sweets and fried and fast food.

The results show that people who scored highest for adhering to the Mediterranean diet had average plaque and tangle amounts in their brains, similar to being 18 years younger than people who scored lowest. In comparison, people who scored highest for adhering to the MIND diet had average plaque and tangle amounts similar to being 12 years younger than those who scored lowest.

Leafy greens for life?
When looking at single diet components, the study showed that people who ate the highest amounts of green leafy vegetables had plaque amounts in their brains corresponding to being almost 19 years younger than people who ate the fewest. 

“Our finding that eating more green leafy vegetables is in itself associated with fewer signs of  Alzheimer’s disease in the brain is intriguing enough for people to consider adding more of these vegetables to their diet,” Agarwal concludes. “Future studies are needed to establish our findings further.”

In related news, a study conducted last found that these diets might also be able to slow the development of Parkinson’s disease.

Edited by William Bradford Nichols