Results from four large population-based studies support a connection between good dietary practices and better cognition in old age.
Peter Sayer, Alison Bloomer, and Eve Batt report from the Alzheimer’s Association International Conference 2017 (AAIC).
A group of US scientists found that, among nearly 6,000 older adults in the Health and Retirement Study, those who consistently followed diets long known to contribute to cardiovascular health were also more likely to maintain strong cognitive function in old age. They found that sticking to the specially designed MIND diet and Mediterranean diet was associated with 30–35% lower risk of cognitive impairment in healthy older adults. In fact, the investigators discovered that those with healthier diets exhibited meaningful preservation of cognitive function.
The Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets were originally developed or codified to help improve cardiovascular health.
A hybrid of these diets, called the Mediterranean- DASH Intervention for Neurodegenerative Delay, or MIND diet, is gaining attention for its potential positive effects on preserving cognitive function and reducing dementia risk in older individuals. A 2015 study found that individuals adhering to this diet exhibited less cognitive decline as they aged.
Other diet-related studies reported at AAIC 2017 included:
- Researchers from the Karolinska Institute in Sweden found that—in a group of more than 2,200 older adults—people sticking to a Healthy Nordic Diet (including non-root vegetables, certain fruits, fish and poultry) enjoyed better cognitive status than individuals who ate a less healthy diet.
- From more than 7,000 participants in the US— based Women’s Health Initiative Memory Study, researchers found that older women who ate diets traditionally thought of as heart-healthy, in particular the MIND Diet, were less likely to develop dementia.
- A team of researchers at Columbia University presented data suggesting that poor diet may promote premature signs of brain ageing through inflammatory mechanisms, which were also associated with smaller brain volume.
Keith Fargo, PhD, Alzheimer’s Association Director of Scientific Programs and Outreach, said:“Although the idea that a healthy diet can help protect against cognitive decline as we age is not new, the size and length of these four studies demonstrate how powerful good dietary practices may be in maintaining brain health and function. That said, we must understand that what we eat is just one part of the puzzle. Adapting our lifestyles as we get older—for example by exercising regularly, watching what we eat and engaging in lifelong learning—is important in order to maximize the potential to reduce risk of cognitive decline and dementia.”
Heart healthy is brain healthy
Claire McEvoy, PhD, at the University of California, San Francisco, and colleagues examined the association between adherence to the Mediterranean and MIND diets and cognitive performance in a large, nationally representative population of 5,907 older, communitydwelling adults in the Health and Retirement Study.
The researchers found that the more healthfully people ate, the better they functioned cognitively. After controlling for demographic, lifestyle and health variables, participants who were highly adherent to these diets were 30–35% less likely to exhibit poor performance on a measure of cognitive function. Study participants who were moderately adherent to either diet were 18% less likely to exhibit signs of cognitive impairment.
Benefits of a healthy nordic diet
Weili Xu, PhD, at the Karolinska Institute, Stockholm, and colleagues sought to identify dietary habits associated with preserved cognitive function in 2,223 community-dwelling, dementia-free adults in Sweden. The investigators found during six years of follow-up that even moderate adherence to a healthy diet known as the Nordic Prudent Dietary Pattern (NPDP) resulted in better cognitive status than individuals who ate a less healthy diet that included fatty foods, sweets and processed foods. In this population, NPDP was found to be a better predictor of preserved cognitive function than the MIND diet, Mediterranean diet, DASH diet and Baltic Sea Diet.
The NPDP included:
- More frequent consumption of non-root vegetables, apple/pears/peaches, pasta/rice, poultry, fish, vegetable oils, tea and water, and light to moderate wine intake.
- Less frequent intake of root vegetables, refined grains/cereals, butter/margarine, sugar/sweets/ pastries, and fruit juice.
Women who eat well are less likely to develop dementia
Research published in 2015 found that the MIND diet was associated with a reduced incidence of Alzheimer’s disease in a sample of 923 older individuals.
Kathleen Hayden, PhD, of Wake Forest School of Medicine in Winston-Salem, North Carolina, and colleagues sought to replicate these findings in 7,057 women participating in the Women’s Health Initiative Memory Study (WHIMS). Using data from WHIMS, they categorised the participants (mean age 71) into quartiles based on level of adherence to the MIND diet, with the 1st quartile being least adherent and the 4th being the most adherent. There were 615 incident cases of Alzheimer’s during a mean follow-up of 9.7 years.
Compared with women in the first (lowest) quartile of MIND adherence, WHIMS participants in the 2nd, 3rd, and 4th quartiles had 24%, 21%, and 34% reductions in the risk of developing Alzheimer’s. It is noteworthy that the largest share of the risk reduction occurred from the poorest dietary habits to the modestly adherent diet. These results corroborate results from previous research in smaller populations, and suggest that it may not require wholesale diet changes to help preserve the aging brain.
Poor diet linked to inflammation
Building on solid evidence that eating well is brain healthy, researchers are beginning to explore mechanisms through which dietary mechanisms may influence cognitive status and dementia risk. Yian Gu at Columbia University, New York, and colleagues examined whether an inflammation-related nutrient pattern (INP) was associated with cognitive function and structural MRI findings in the brain.
Using data on 330 community-dwelling, nondemented elderly individuals (mean age 79.7), the investigators found that an INP characterised by high intake of cholesterol, beta-carotene and lutein, and low intake of omega-3 polyunsaturated fatty acids, calcium, folate and vitamins (B1, B2, B5, B6, D, E), was positively associated with levels of inflammatory markers (C-reactive protein and interleukin-6). In addition, closer adherence to this INP was associated with smaller total brain gray matter volume and worse performance in executive function. Additional research in larger populations is needed to confirm the role of inflammation-related dietary components in brain and cognitive health, and help elucidate inflammatory or other mechanisms through which eating habits may alter brain function and structure.