Eating a high-quality diet during youth and middle age may help your brain function well into old age, according to a new study.

The study, conducted on more than 3,000 people over nearly seven decades, shows that a healthy diet may help prevent Alzheimer’s disease and age-related cognitive decline.

Most studies have focused on the eating habits of people in their 60s and 70s.

This new study is the first to track diet and cognitive ability from ages 4 to 70, showing that diet affects cognitive health much earlier than previously thought.

“These findings support the idea that adopting healthy dietary patterns early in life is important for maintaining health throughout life,” said Kelly Caira of the Friedman School of Nutrition Science and Policy at Tufts University.

Kaira presented the study at NUTRITION 2024, the annual meeting of the American Society for Nutrition, in Chicago.

Cognitive performance is usually better in middle age, but begins to decline after age 65. Serious conditions such as dementia can also develop with age.

Researchers found that a diet rich in plant-based foods, antioxidants, and healthy fats promotes brain health by reducing oxidative stress and improving blood flow to the brain.

The study analyzed data from 3,059 U.K. adults who were part of the 1946 British Birth Cohort. This group provided dietary and cognitive data over 75 years. The researchers found that diet quality was closely linked to trends in cognitive ability.

For example, only 8% of people with a low-quality diet had higher cognitive ability over time, while only 7% of people with a high-quality diet had lower cognitive ability.

At ages 68-70, participants with the highest cognitive scores had better working memory, processing speed and overall cognitive performance than those with the lowest scores. About a quarter of participants in the lowest cognitive group showed signs of dementia, while none in the highest group did.

The study also stated that diet quality in childhood influenced dietary patterns in later life.

“Early dietary choices influence our later life decisions, which have long-term effects on cognitive abilities,” Kaira said.

The researchers used the 2020 Healthy Eating Index to measure diet quality, finding that people with the highest cognitive ability ate more vegetables, fruits, legumes and whole grains, and less sodium, added sugars and refined grains.

“A diet rich in less-processed plant-based foods such as leafy vegetables, legumes, whole fruits and grains is most protective,” Carra said. “Including these foods in your diet at any age may improve overall health, including cognitive health.”

The majority of study participants were Caucasian from the UK, so further research is needed to see if the results apply to more diverse populations. Despite some data gaps, the researchers created global cognitive ability scores to compare participants of each age over time.