Nutrition and Dementia among Older Adults

Speaker: Carol Greenwood, PhD, Professor, Department of Nutritional Sciences, University of Toronto; Senior Scientist, Kunin-Lunenfeld Applied Research Unit, Baycrest Centre, Toronto, ON.

Dr. Carol Greenwood contextualized her discussion’s theme of nutrition and dementia as contributing to considerations of the environmental influences posing risk for cognitive decline and dementia. While dementia has important genetic roots, a large causative factor is environmental exposure. In cases of disease onset at >80 years of age, studies have suggested that ~60% relates to this factor.

Dietary Patterns that Increase Risk of Cognitive Decline
To understand the risk mediated by environmental exposure, she recommended that listeners focus on chronic diet rather than on instances of good or poor intake. The connection between nutrition and dementia relates to the underlying idea that neurons require nutritional support; altered nutrition equates to altered neuronal metabolism. Sound nutrition maintains brain insulin signaling, needed for learning and memory. Clinicians should aim to promote dietary habits that maintain brain neurotrophin levels, which support synaptic plasticity needed for memory consolidation; further, good diet and appropriate nutrient intake can reduce inflammation and oxidative damage, and maintain the cerebrovasculature’s capacity to supply essential nutrients to the brain.

Advances in this area of research could help to remediate an isolationist philosophy that can pervade viewpoints on chronic disease. The brain is highly sensitive to the health of the body, and through dietary modification it is possible to exert direct impact on diet-associated conditions such as cardiovascular disease (CVD), type 2 diabetes, and depression.

Many epidemiologic studies on diet are available, indicating that excess caloric intake leads to oxidative stress. Dr. Greenwood and colleagues have examined the role of fat intake. High fat intake, particularly of saturated and polyunsaturated fats, along with a dearth of Omega fats, are typical of the North American diet. Studies have shown that diets low in fruits, vegetables, whole cereal grains, and low in fish oils are associated with higher risk of dementia. This diet profile also associates with CVD, diabetes, depression, and other inflammatory and chronic disease states. The adverse effects on the brain are not simple, and multiple mechanisms are likely involved; separating the role of chronic disease from a direct impact on brain function would distort the effects.

Fish oils exemplify how individual nutrients can modulate multiple neuronal pathways. Studies involving fish oils and dementia risk have found the individual role hard to isolate because they, as all nutrients, have multiple effects in the body. As the Omega fats are incorporated into dietary recommendations the so-called physiologic role of the nutrient versus the pharmacologic role blurs. Incorporating the Omega fats on a wholistic nutritional basis is the sound approach, one that “nudges” the system. The other seeks to exert a large pharmacological impact with a “targeting and isolating” approach through supplements or food enrichment (e.g., eggs). Such an approach overlooks other aspects of fish protein that are valuable.

Similarly, investigations of health outcomes associated with altered antioxidant exposure have isolated micronutrients and supplied them in supplemental form, producing equivocal data. However, measuring the effects of this consumption should not be extrapolated to the effects of a dietary pattern that incorporates micronutrients on a grams per day nutritional intake. The targeted approach also overlooks that the full nutritional cocktail is more important (e.g., the synergistic aspect) than consuming any one individual compound. Food constituents work together.