Eating a diet high in fruits, vegetables, and legumes; moderate in nuts, fish, and alcohol; and low in meat is associated with better brain health in middle age, according to an observational study published online in Neurology on March 6.
Previous research suggests heart-healthy diets, including the Mediterranean diet and Dietary Approaches to Stop Hypertension (DASH), may protect the brain by slowing down cognitive decline and reducing the risk of dementia. However, these studies focused on older adults and presented inconsistent findings. Few studies have examined whether diet in early adulthood could influence the risk of cognitive impairment in midlife.
To find out, researchers at Queen’s University Belfast in Northern Ireland analyzed data on 2,621 participants (45 percent black; 57 percent women; average age at study start, 25) in the Coronary Artery Risk Development in Young Adults (CARDIA) study to observe the effects of three heart-healthy diets. Dietary patterns were assessed at the start of the study and seven and 20 years later. Cognitive function was evaluated at 25 and 30 years.
The diets were defined as follows: Mediterranean, which emphasizes whole grains, fruits, vegetables, healthy unsaturated fats, nuts, potatoes, legumes, and fish, and limits red meat, poultry, and full-fat dairy. DASH, which emphasizes grains, vegetables, fruits, low-fat dairy, legumes and nuts, and limits meat, fish, poultry, total fat, saturated fat, sweets, and sodium. A Priori Diet Quality Score (APDQS), which emphasizes fruits, vegetables, legumes, low-fat dairy, fish, and moderate alcohol, and limits fried foods, salty snacks, sweets, high-fat dairy, and sugar-sweetened soft drinks.
Researchers measured participants' adherence to the Mediterranean diet based on 11 individual diet components that were scored between 0 and 5 points and then totaled for a score of between 0 and 55 points. Participants accumulated points based on how much they consumed of each food group.
Alcohol consumption was scored 0 for non-consumption or a high intake (more than four and a half drinks per day) for a maximum score of 5 for moderate consumption (up to 2 drinks per day), the researchers reported.
For those who followed the DASH diet, researchers calculated their scores based on 10 diet components. Although alcohol was allowed, it's not part of the dietary plan, since it can increase blood pressure.
Lastly, adherence to the APDQS diet was based on the classification of 46 food groups believed to have beneficial, neutral, or adverse health outcomes. The researchers calculated participants' APDQS scores, ranging from 0 to 132, based on a eating more of 20 beneficial foods, including fruit, vegetables, legumes, low-fat dairy, fish, and moderate alcohol intake, and eating less of 13 adverse foods, such as fried foods, salty snacks, desserts, high-fat dairy, and sugar-sweetened soft drinks.
Based on the participants' responses to questionnaires that measured their diet adherence at the study start, at year 7, and year 20, the researchers divided them into one of three groups: low, medium, or high.
To test participants’ mental acuity, researchers administered a series of cognitive tests that assessed verbal learning and memory (the number of words correctly recalled after a 10-minute delay) and processing speed and executive function (organizing and planning) at years 25 and 30.
Based on participants overall scores for diet adherence and performance on cognitive tests and after adjusting for education, smoking, diabetes, and physical activity, researchers found that participants who closely followed the Mediterranean diet were 46 percent less likely to have poor cognitive function than those who didn’t.
Of the 868 people with high adherence to the Mediterranean diet, 9 percent had poor cognitive function, compared to 29 percent of the 798 people who had lower scores.
Among the APDQS group, those who adhered closely to the diet were 52 percent less likely to have poor cognitive function than people with low adherence. Of the 938 people in the high group, 6 percent had poor cognitive function, compared to 32 percent of the 805 people in the low group.
No association was found with the DASH diet, which does not recommend alcohol consumption.
"Moderate alcohol is recommended in both the Mediterranean diet and APDQS but is not considered in the DASH score system, suggesting that moderate alcohol intake as part of a healthy diet could be relevant for brain health in midlife," the researchers speculated.
The findings do not prove that following a heart-healthy diet leads to better cognitive function; it only shows an association between the two.
Furthermore, the study did not find any associations between eating specific foods in the diets and cognitive performance. The combination of foods that make up these diets is what’s vital for brain health, the researchers noted.
"Additional studies are needed to define the combination of foods and nutrients for optimal brain health across the life course," they concluded.
For more about brain-healthy diets, read Brain Food.
