Can Better Nutrition Reduce The Risk Of Alzheimer's Disease?

​Max Wallack, Harvard Medical Student

Have you ever wondered what you can do to reduce your risk of developing Alzheimer’s disease?  A healthy diet may be one important way in which you can lower your risk.

Alzheimer’s disease develops at least a decade before symptoms appear. The long lag time makes it difficult to do randomized controlled trials testing how dietary habits may influence Alzheimer’s disease risks. Most evidence therefore comes from observational studies that follow large populations over long periods of time, comparing the dietary patterns and other characteristics of people who later develop Alzheimer’s with those who do not.
 
The highest confirmed rates of Alzheimer’s disease are in wealthy countries where red meat consumption is high; lower rates are documented in Okinawa and in certain parts of southern Europe where diets are high in fish, high in fresh vegetables, and low in red meat. While genetics do play a role in who will get Alzheimer's disease, many immigrant populations in the United States, such as those of Japanese or African descent, have higher rates of Alzheimer’s disease than populations still living in their native countries. In communities where dietary habits have changed, Alzheimer’s rates have changed with them.
 
Most studies on dietary patterns investigate their relationship with risk for cardiovascular disease and diabetes. Multiple studies have identified Mediterranean diets, high in fish, fresh plant foods, whole grains, and healthy fats as capable of significantly lowering these disease risks over time.  Along with the very similar DASH, MIND, and MPN diets, Mediterranean diets emphasize these fresh foods, along with an emphasis on olive oil and less saturated fat, and alternate sources of protein such as beans, nuts, and seeds.  It turns out that these same diets appear to lower risk for Alzheimer's. This could be for several reasons. People with type 2 diabetes are at increased risk for developing dementia; in one study of people over 55 years old, participants with diabetes were 65% more likely to develop Alzheimer’s disease. Lowering risk for diabetes might have some payoff for Alzheimer’s as well. But, clinical trials also directly show that better adherence to healthy dietary patterns can also lower the risk for Alzheimer's disease.
 
In particular, fish might have several benefits, with the omega-3 fatty acid docosahexaenoic acid (DHA), found in many cold-water fishes, possibly being protective against the damage caused by high-fat diets. Many studies have found slower cognitive decline and lower rates of Alzheimer’s disease among those who ate more fish. One study of 815 adults, aged 65 to 94, found that those who ate fish at least once a week had a 60% lower risk of developing Alzheimer’s disease, compared to those who ate fish rarely or not at all. A multivariate study of 30 serum biomarkers found that biomarkers indicative of higher omega-3 fatty acid consumption were associated with higher cognitive function and less loss of brain volume. A 2018 meta-analysis found that, overall, closer adherence to a Mediterranean diet resulted in better and more lasting brain health, including lower levels of one of the hallmark proteins of Alzheimer’s disease – amyloid β (Aβ) – in the brain. An extensive review found that consumption of fish, fruits, vegetables, nuts, whole grains, coffee, green tea, and the antioxidants and B vitamins that they contain, are all beneficial for reducing Alzheimer’s risk, while high-carbohydrate diets were associated with increased risk.
On the flip side, a study of over 6000 Chicago residents found a doubling of the risk for Alzheimer’s disease among those who ate the most saturated fats, compared to those who ate the least.
 
All these findings point to the increasing likelihood that better dietary habits can reduce your risk of developing Alzheimer’s disease.  Regular exercise increases both the neurological and cardiovascular benefits of a healthy diet, further decreasing the risk of developing Alzheimer's disease and also prolonging life in a dose-responsive manner. The same measures that improve cardiovascular health also seem to improve brain health, and the choices that we make can definitely lower our individual risk of developing Alzheimer’s. 

About the Author: 
Max Wallack is a student at Harvard Medical School, class of 2020. He graduated summa cum laude from Boston University in 2015. He previously worked as a research trainee in the Department of Pharmacology and Experimental Therapeutics at Boston University School of Medicine, where he coauthored multiple publications on Alzheimer’s disease. In 2008, Max founded a nonprofit organization, PuzzlesToRemember, which has since provided therapeutic puzzles to over 6,000 facilitiies worldwide. He also wrote a book, since translated into 11 languages, explaining Alzheimers disease to children. He is currently a research assistant at Brigham and Women's Center for Neurological Imaging, focusing on the temporal effects of Multiple Sclerosis lesions on white matter tracts. Max’s primary interests are focused in neuroradiology, particularly in neurodegenerative diseases.