Elevated inflammation and insulin levels are both tied to an accelerated risk of cognitive decline.ANDREW BUI/The New York Times
The foods you eat – and the ones you don’t – have gained considerable scientific attention as a major factor in healthy aging.
Diet quality is known to be a leading risk factor for chronic disease and premature death.
Now, new evidence adds strong support to the protective link between a healthy diet and living longer in good health, in particular when it comes to brain health.
What’s more, the findings underscore the importance of starting early on a healthy eating plan to help stay cognitively fit as you age.
Here’s what to know about the study, its findings and a brain-friendly eating pattern to model your diet after.
The latest research
For the study, published Feb. 23 in JAMA Neurology, researchers investigated the relationship between adherence to six established healthy dietary patterns and cognitive decline.
To do so, they analyzed data from 159,347 men and women who were enrolled in three major long-running U.S. studies. Participants, with an average age of 44 years when the study began, were followed for 26 to 28 years.
During that time, diet information was collected every four years and was used to calculate how closely participants’ diets matched each dietary pattern.
These included the Alternative Healthy Eating Index, the Dietary Approaches to Stop Hypertension (DASH) diet score, the Healthful Plant-Based Diet Index, the Planetary Health Diet Index and two research-based scores that measured the potential of a person’s diet to increase inflammation and insulin in the bloodstream (hyperinsulinemia). Elevated inflammation and insulin levels are both tied to an accelerated risk of cognitive decline.
As well, participants answered questionnaires that assessed their self-reported perception of worsening memory and thinking skills. Subjective cognitive decline is considered an early warning sign of future cognitive impairment.
A subset of participants also underwent periodic cognitive testing to evaluate their memory, attention and global cognitive function (an average of all cognitive tests).
Healthy eating benefits cognitive health
Higher adherence across all six healthy diet patterns was associated with a lower risk of subjective cognitive decline.
The blood-pressure-lowering DASH diet, however, had the strongest effect: Participants with the highest versus the lowest adherence scores were 41 per cent less likely to report significant subjective cognitive decline.
Higher DASH diet scores were consistently linked to a lower risk of subjective cognitive decline even when diet was measured in midlife (45 to 54 years), 26 years earlier than participants’ cognition was assessed.
This finding aligns with emerging evidence that midlife is a critical period for diet to influence later-life cognitive function.
Higher adherence to the DASH diet also showed the strongest association with higher scores on cognitive function tests.
To arrive at these conclusions, other factors that influence cognitive aging were accounted for, including education level, family history of dementia, physical activity, alcohol intake, smoking status and the presence of high blood pressure, elevated cholesterol, diabetes, stroke and depression.
Don Chen/Getty Images/iStockphoto
When the researchers looked at specific food groups, higher intakes of green leafy vegetables, yellow and red vegetables, tomatoes, whole fruit, pulses (beans, chickpeas, lentils) and fish were significantly associated with better cognitive scores.
Higher intakes of processed meat, sugary drinks and sweets were tied to poorer cognition.
Caveats and key takeaways
The study was observational and doesn’t provide direct proof that eating a healthy diet delays cognitive decline.
As well, study participants were highly educated and predominantly white, so the findings may not apply to more diverse populations.
The study’s strengths, though, lie in its large sample size, long-term follow-up and repeated dietary questionnaires which help to minimize errors of self-reported recall.
The finding that all six healthy diet patterns reduced the risk of subjective cognitive decline adds to existing evidence that a diet plentiful in vegetables, fruit, fish and plant proteins – while low in added sugars and processed meats – promotes healthy brain aging.
And especially so if such an eating pattern is followed in midlife.
About the DASH diet
In addition to improving brain health, the well-researched DASH diet has been associated with reducing inflammation, elevated blood pressure, high cholesterol, as well as the risk of heart disease, Type 2 diabetes and colorectal cancer.
The diet emphasizes fruits and vegetables, whole grains, low-fat dairy products, pulses (beans and lentils), nuts and seeds.
Foods high in saturated fat, such as fatty meats and full-fat dairy, are limited, as are sweets and alcoholic beverages. Sodium is restricted to 1500 or 2300 mg a day.
The DASH diet outlines daily or weekly servings of foods based on a person’s daily calorie needs.
For example, if you follow a 2,000-calorie diet, the plan recommends eating each day 4 to 5 vegetable servings, 4 to 5 fruit servings, 2 to 3 low-fat dairy servings, 6 to 8 whole-grain servings and 6 ounces of lean meat, poultry or fish.
As well, 4 to 5 weekly servings of pulses, nuts and/or seeds are recommended.
The U.S. Heart, Lung and Blood Institute is a recommended resource to learn about the DASH eating plan for various calorie levels.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan.
