New research finds that following a diet rich in plant-based foods and low in animal products during midlife is associated with a significantly lower risk of cognitive impairment later in life.

According to the latest estimates from the United Nations, there are currently 137 million people over the age of 80 worldwide. Experts expect this number to triple by 2050, reaching 425 million.

The number of people with Alzheimer disease and other forms of dementia is also on the rise. According to the Centers for Disease Control and Prevention (CDC), in the United States alone, there are currently 5 million adults living with Alzheimer. This number is also likely to triple within the next few decades.

As the population continues to age, it is becoming increasingly important to be able to identify modifiable risk factors for conditions such as Alzheimer, as well as any lifestyle changes that may prevent neurodegenerative conditions such as this from developing in the first place.

New research points to nutrition as one such factor. Eating a diet rich in fruits, vegetables, and whole grains and low in animal products such as meat and dairy lowers the risk of cognitive decline in later life, suggests the new study.

Koh Woon Puay, a professor at the National University of Singapore's (NUS) Saw Swee Hock School of Public Health and the Duke-NUS Medical School, is the principal investigator of the study. The team's results appear in the American Journal of Clinical Nutrition.

Studying diets and cognitive health

Prof. Puay and colleagues examined data available from the Singapore Chinese Health Study, a population cohort study of 63,257 Chinese people living in Singapore.

As part of this initial study, adults aged 45–74 provided information during face-to-face interviews about their "usual diet, cigarette smoking, alcohol consumption, physical activity, sleep duration, height, weight, and medical history."

This occurred at baseline, between April 1993 and December 1998. Researchers interviewed the participants again during three follow-up visits, until 2016.

For the new study, Prof. Puay and colleagues used these data to select information on 16,948 people—aged 53, on average—at baseline. These participants only completed cognitive function assessments during their third follow-up visit, in 2014–2016.

To assess the participants' eating habits, the researchers used five dietary patterns:

• the "alternative Mediterranean diet," which is a tweaked version of the typical Mediterranean diet
• the Dietary Approaches to Stop Hypertension (DASH) diet
• the alternative Healthy Eating Index
• the plant-based diet index
• the healthful plant-based diet index

All of these diets are similar in their emphasis on plant-based foods. The latter two indexes assign positive scores to eating plant-based foods and reverse scores for eating less healthful plant foods or animal foods.

Up to 33% lower risk of cognitive decline

In 2014–2016, 2,443 of the participants (14.4% of them) had cognitive impairment.

The researchers found that people who had strongly adhered to the five dietary patterns outlined above during midlife were less likely to develop cognitive impairment later on.

Specifically, those whose diets the researchers deemed most similar (in the top 25%) to those five dietary patterns were 18–33% less likely to develop cognitive impairment than those with the least similar diets (in the bottom 25%).

Prof. Puay comments on the significance of the findings in the larger scheme of existing research. She says, "Previous studies have shown mixed results when it comes to diet and the risk of cognitive impairment, with few studies conducted in Asian populations."

"Our study suggests that maintaining a [healthful] dietary pattern is important for the prevention of onset and delay of cognitive impairment."

—Prof. Koh Woon Puay

"Such a pattern," she adds, "is not about the restriction of a single food item but the composition of an overall pattern that recommends cutting back on red meats, especially if they are processed, and including lots of plant-based foods (vegetables, fruit, nuts, beans, whole grains) and fish."