VIENNA—The low-fat, high-fiber diet recommended for lowering blood pressure may help to attenuate age-related cognitive decline and lower the risk for dementia, researchers reported here.
Known as the Dietary Approaches to Stop Hypertension (DASH) diet, the plan emphasizes fruits and vegetables, nuts and legumes, whole grains, and low-fat dairy products. Sodium, sweets, and red meats are to be consumed sparingly.
In a new study, the greater a person's adherence to the DASH diet, the slower the rate of cognitive decline, according to a team led by Heidi J. Wengreen, PhD, RD, assistant professor of nutrition at Utah State University in Logan.
“It made sense to study this. Hypertension in midlife is a strong risk factor for Alzheimer disease and dementia, and the DASH eating plan has been proven to lower blood pressure,” said co-author Ronald Munger, PhD, a professor in the department of nutrition and food sciences at Utah State, who described the findings here at the International Conference on Alzheimer's Disease.
The study involved 3,831 people ages 65 and older with no signs of dementia participating in the Cache County (Utah) Study on Memory, Health and Aging.
At baseline, they filled out a 142-item food frequency questionnaire, assigned a score based on how closely they followed the diet, and divided into quintiles.
Cognitive function was assessed using the 100-point Modified Mini-Mental State Examination (MMSE) at baseline and at three other time points over an 11-year period.
The researchers found that those in the highest quintile had the highest MMSE scores at baseline and the least decline in scores over time.
Specifically, those in the highest quintile scored 1.42 points higher on the MMSE at baseline and 1.81 points higher after 11 years than did those in the lowest quintile of the DASH score, with both figures reaching statistical significance, Dr. Munger said.
Further analysis showed that four of the nine food-group/nutrient components used to create the DASH score — vegetables, whole grains, low-fat dairy, and nuts/legumes — were independently associated with higher MMSE scores, he added.
When participants were divided into quintiles based only on their adherence to these four food groups, those in the highest quintile scored 1.72 points higher at baseline and 3.72 points higher after 11 years than did those in the lowest quintile, with the figures again reaching statistical significance, Dr. Munger said.
Those in the highest quintile of the four-component score also had a lower risk of developing dementia than did those in the lowest quintile, but this finding was only significant for those without the APOE e4 allele, he added.
“Over the years, researchers have tried to slow cognitive decline using single nutrients and supplements, with mixed results. We believe that what we have observed is that the total diet is greater than the sum of its parts,” Dr. Munger said.
The DASH diet isn't easy to follow, he acknowledged. It calls for eight to 10 servings of fruits and veggies a day, for example, and “only about 25 percent of Americans eat even five servings a day,” Dr. Munger said.
Also, the observational study doesn't prove that the diet itself slows cognitive decline. It could be the diet itself or some other lifestyle factor shared by people who eat well that is responsible for the protective effect, he said.
On the other hand, DASH is proven safe and effective at lowering blood pressure, “so there's no reason not to follow it,” Dr. Munger said.
Samuel E. Gandy, MD, PhD, Mt. Sinai Professor of Alzheimer's Disease Research, Professor of Neurology and Psychiatry, and associate director of the Mt. Sinai Alzheimer's Disease Research Center at Mt. Sinai School of Medicine in New York, said that “since there clearly seems to be a connection between risk factors for heart disease and risk factors for Alzheimer disease, [the DASH diet] may slow the development of vascular dementia by treating these cardiac risk factors.
“It might not be directly acting on Alzheimer disease, but rather may be treating the vascular part of the dementia that's driving Alzheimer disease” in some patients, he said.
The DASH Diet
The DASH plan calls for:
- Grains: Six to eight daily servings, with a typical serving being one slice of bread or one-half cup of cooked rice or cereal.
- Vegetables: Four to five daily servings, with a typical serving being one cup of raw leafy vegetables or one-half cup of cooked vegetables.
- Fruits: Four to five daily servings.
- Low-fat or fat-free dairy products: Two to three daily servings, with a typical serving being one cup of milk.
- Nuts, seeds, and dry beans: Four to five servings per week, with a typical serving being 1.5 ounces of nuts or 2 tablespoons of peanut butter.
- Fats and oils: Two to three daily servings, such as one teaspoon of margarine or one tablespoon of mayonnaise.
- Meat, poultry, and fish: Six or fewer one-ounce daily servings.
- Sweets and added sugars: Five or fewer weekly servings, with a typical serving being one tablespoon of sugar or one-half cup sorbet.