Diet's Role in Modifying Risk of Alzheimer's Disease: History and Present Understanding

Abstract

Diet is an important nonpharmacological risk-modifying factor for Alzheimer's disease (AD). The approaches used here to assess diet's role in the risk of AD include multi-country ecological studies, prospective and cross-sectional observational studies, and laboratory studies. Ecological studies have identified fat, meat, and obesity from high-energy diets as important risk factors for AD and reported that AD rates peak about 15-20 years after national dietary changes. Observational studies have compared the Western dietary pattern with those of the Dietary Approaches to Stop Hypertension (DASH), Mediterranean (MedDi), and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets. Those studies identified AD risk factors including higher consumption of saturated and total fats, meat, and ultraprocessed foods and a lower risk of AD with higher consumption of fruits, legumes, nuts, omega-3 fatty acids, vegetables, and whole grains. Diet-induced factors associated with a significant risk of AD include inflammation, insulin resistance, oxidative stress, elevated homocysteine, dietary advanced glycation end products, and trimethylamine N-oxide. The molecular mechanisms by which dietary bioactive components and specific foods affect risk of AD are discussed. Given most countries' entrenched food supply systems, the upward trends of AD rates would be hard to reverse. However, for people willing and able, a low-animal product diet with plenty of anti-inflammatory, low-glycemic load foods may be helpful.

Keywords: Advanced glycation end products; Alzheimer’s disease; TMAO; dementia; diet; meat; neuroinflammation; obesity; saturated fat; ultraprocessed foods.

Fig. 1

Correlation between prevalence of AD for 11 countries in the 1997 study [8] with respect to dietary meat supply obtained from the Food and Agriculture Organization. AD, Alzheimer’s disease.

Fig. 2

Comparisons of risk of three dietary patterns with respect to the WD based on data from the seminal studies.

Fig. 3

Obesity rate for adults in the US versus year and AD mortality rates (number/100,000/year times 0.676) versus year minus 20 years. AD, Alzheimer’s disease.

Fig. 4

Effects of specific dietary food groups and factors on risk of AD.