Potential role of dietary whole grains in Alzheimer's disease: bioactive components, mechanistic insights, and epidemiological evidence

Background: Alzheimer's disease (AD) is an aging-related neurodegenerative disease leading to memory loss, cognitive impairment, dementia and even death. The risk of AD is exacerbated by the aging of the global population, as well as other causes such as COVID-19 pandemic. Current treatments for AD have a variety of side effects. Scope and approach: The effect of whole grains on AD has great potential as a novel strategy to reduce the risk of developing AD. This review aims to examine the role of whole grains in different dietary patterns, summarize the preclinical AD-protective effects of whole grains, and explore the epidemiological link of whole grains and AD risk. This review summarized the recent research in animal models and human studies of whole grains and their bioactive components in AD modulation, with insights into modern food processing methods on nutritional characteristics of whole grains. Key findings and conclusions: Studies demonstrated that plant-based dietary patterns, including the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets, are associated with improved symptoms of AD. Among components of these diets, whole grains exhibit significant individual benefits to AD. Whole grains are rich in dietary fiber, polyphenols, B vitamins, vitamin E, and betaine, which can reduce oxidative stress and neuroinflammation, modulate gut-brain axis, and protect neurons, thereby potentially improving cognitive performance. Furthermore, modern food processing technologies affect the neuroprotective properties of whole grains. These findings highlight the potential of whole grains as a dietary intervention for AD and the underlying mechanisms.