Stephanie Rainey-Smith

The purpose of this chapter is to (1) examine research published from human studies in order to evaluate the role of the Dietary Approaches to Stop Hypertension (DASH) diet and the associated Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet in brain aging, particularly cognitive decline, and (2) discuss potential mechanisms of action underlying the observed benefits. A variety of cognitive functions decline with advancing age; however, such decline is amplified and accelerated with pathological aging, such as Alzheimer disease (AD) and other forms of dementia. Thus, strategies which maintain cognition with advancing age are also likely to delay onset or potentially decrease risk of AD and dementia. Numerous research studies suggest that dietary interventions may confer some protection against cognitive decline. The DASH diet is comprised of healthy foods such as fruits, vegetables, and low-fat dairy products, and is designed to be reduced in fats and higher in protein, minerals, and fiber. The MIND is a combination of the DASH and Mediterranean diets, and focuses on consumption of green leafy vegetables and berries. The available evidence suggests that the DASH and, to a greater extent, the MIND dietary pattern, may provide protection against neurodegeneration during aging. These dietary patterns may exert their beneficial effects through improving AD risk factors that ultimately benefit brain health, such as reducing CVD and diabetes indices, preserving telomere length, and reducing oxidative stress and neuroinflammation. Further prospective studies conducted in diverse populations, and adequately powered intervention studies, using larger sample sizes and longer durations, are required to examine the effect of dietary pattern consumption on clinically relevant cognitive outcomes, and structural and functional brain changes. Such studies are of critical importance given the increasing prevalence of AD and other dementias.

Whilst the links between a healthy diet and healthy heart are firmly established and well documented, the relationship between diet and brain health is less well understood. Emerging research is ensuring however, that the maxim of ‘what is good for your heart, is also good for your brain’ is gaining momentum. Nutritional status and dietary habits have long been known to influence risk of cardiovascular disease (CVD) and type 2 diabetes mellitus (T2D), and they are now materialising as key factors influencing Alzheimer's disease (AD) risk. This is compounded by the fact that both CVD and T2D are themselves risk factors for AD, and also by the fact that AD is an age‐related condition, and ageing is accompanied by an overall decline in digestive function, absorptive capabilities, and the assimilation of nutrients. Therefore, understanding the effect of macro‐ and micronutrients on neuronal biochemistry and AD pathology will provide opportunities for dietary manipulation to promote neuronal resistance to insults and reduce brain injury. This chapter discusses some of the key nutrients involved both directly in neuronal biochemistry, and indirectly by influencing peripheral metabolism, which in turn can modulate AD pathology.