What you eat has a major impact on risk of Alzheimer’s disease - study

Alzheimer’s disease (AD) is linked with age and genetics, so it has been said that there is little one can do to prevent it—except maybe to exercise one’s brain with reading, crosswords or sudoku. But now, researchers in California and Hawaii have discovered that people can take action to reduce their risk of this most common type of dementia.

In a detailed study entitled “Diet’s Role in Modifying Risk of Alzheimer’s Disease: History and Present Understanding” just published in the Journal of Alzheimer’s Disease, the scientists suggest that eating certain foods regularly is beneficial in cutting the risk. Diets that are more plant based, like the Mediterranean diet—consumed for many years in Israel before the population got used to eating junk food—and traditional diets in China, Japan, and India, are shown to reduce risk, especially when compared to the Western diet.

Rates of AD rise in these countries as they make the nutrition transition to a Western diet. Risk factors include a higher consumption of saturated fats, meat—especially red meat such as hamburgers and barbeque as well as processed meats such as hot dogs—and ultra-processed foods high in sugar and refined grains.

The study explains why certain foods increase or reduce the risk of dementia. For example, meat raised the danger of AD the most by raising risk factors such as inflammation, insulin resistance, oxidative stress, saturated fat, advanced glycation end products, and trimethylamine N-oxide, a molecular metabolite that can predict major adverse cardiovascular events, like heart attack, stroke and death.

The study also outlines several foods that are protective against AD including green leafy vegetables, colorful fruits and vegetables, legumes (like beans), nuts, whole grains and omega-3 fatty acids.

The authors—Dr. William Grant of the Sunlight, Nutrition, and Health Research Center in San Francisco and Dr. Steven Blake, a nutritional biochemist at the Maui Memory Clinic in Wailuku—make a strong case that, while further research is needed to better understand the mechanisms, diet and lifestyle factors linked to diabetes, cardiovascular disease and some cancers are likely to also influence the risk of developing AD.

Danger of ultra-processed foods

Ultra-processed foods can increase the risk of obesity and diabetes, themselves risk factors for AD. Ultra-processed foods often lack the very ingredients found in whole plant foods that keep dementia away such as anti-inflammatory components and antioxidants.

Poverty is an important driver of Alzheimer’s disease in the West because ultra-processed foods and meat are cheaper sources of energy than fruits, vegetables, whole grains, and other more nutritious foods, thus promoting obesity.

For example, AD rates in the US are expected to rise 50% by 2038 from 2018 levels. This calculation is based on comparing trends of obesity in America with trends of dementia. This comparison shows a 20-year lag between obesity rates and AD rates. Although one’s personal risk of AD can be minimized with diet, it is expected that those who persevere in consuming a Western diet will continue to have a higher risk.

“Grant and Blake comprehensively review and synthesize the role of dietary factors in Alzheimer’s disease,” Nutrition and epidemiology Prof. Edward Giovannucci at Harvard University said. 

“Evidence from diverse perspectives supports that a diet that emphasizes fruits, vegetables, legumes, nuts, whole grains, and… de-emphasizes meat, especially red meat, saturated fats, and ultra-processed foods is associated with lower risk of Alzheimer’s disease. Physical inactivity and obesity also contribute to higher risk," he said.

“In addition, the dietary and lifestyle patterns associated with higher risk of Alzheimer’s disease are known to affect the constellation of mechanisms believed to increase risk, including inflammation, insulin resistance and oxidative stress, among others,” Giovannucci   said, concluding that “their work provides an excellent overview of modifiable risk factors for this type of dementia.”