30-year study links dietary patterns to healthy ageing at 70

Ageing is unavoidable, yet for some people it arrives sooner or more harshly than for others.

How we grow older is shaped in part by things we cannot easily change, such as our genetics and exposure to environmental pollutants. Even so, evidence indicates we can still tilt the odds through everyday behaviour - particularly our sleep, physical activity, and diet.

What the 30-year study on diet and healthy ageing examined

In a newly reported study spanning three decades, scientists explored in detail how eating patterns relate to healthy ageing. In this research, healthy ageing meant reaching 70 without major chronic illness and without meaningful declines in cognitive ability, physical function, or mental health.

Co-author Frank Hu, an epidemiologist at Harvard University, says the work is among the first to compare several dietary patterns in midlife against an overall measure of healthy ageing.

"Studies have previously investigated dietary patterns in the context of specific diseases or how long people live," Hu says. "Ours takes a multifaceted view, asking, 'How does diet impact people's ability to live independently and enjoy a good quality of life as they age?'"

To do this, Hu and colleagues analysed long-term data from 105,000 adults aged 39 to 69 (with an average age of 53), collected from 1986 to 2016 through the Nurses' Health Study and the Health Professionals Follow-Up Study.

Participants completed dietary questionnaires repeatedly throughout the 30-year period. The research team then rated each person’s diet by how closely it matched eight established dietary patterns, aiming to identify which pattern was most strongly linked with healthy ageing.

Eight dietary patterns assessed

The eight dietary patterns were: the Alternative Healthy Eating Index (AHEI), the Alternative Mediterranean Index (aMED), the Dietary Approaches to Stop Hypertension (DASH), the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND), the healthful plant-based diet (hPDI), the Planetary Health Diet Index (PHDI), the empirically inflammatory dietary pattern (EDIP), and the empirical dietary index for hyperinsulinemia (EDIH).

Although distinct, the researchers point out that these patterns share broad themes, including prioritising whole plant foods and healthier fats.

Alongside these eight patterns, the study also considered intake of ultra-processed foods - industrially manufactured products that often contain long ingredient lists and high levels of sugar, salt, and less healthy fats.

Which dietary pattern performed best for healthy ageing: AHEI

Using their definition, 9,771 people qualified as experiencing healthy ageing, equal to 9.3 per cent of the overall sample.

Across the board, greater adherence to any of the eight dietary patterns was linked with a higher likelihood of healthy ageing. In other words, following any one of them was associated with better odds of remaining in good shape at 70.

The authors note this points away from a simple, universal answer, and suggests there is no single best diet for everyone. Even so, one pattern emerged as the strongest overall.

According to the results, the AHEI was the top-performing diet pattern for healthy ageing. The researchers describe it as similar to the earlier Healthy Eating Index, but designed more explicitly around reducing chronic disease risk.

Those in the highest fifth (top quintile) of AHEI adherence were 86 per cent more likely to achieve healthy ageing at 70 than participants in the lowest quintile. When the threshold was moved to age 75, people in the top quintile were 2.24 times likelier to age healthily.

The AHEI pattern centres on plant-based foods - including fruit, vegetables, whole grains, nuts, and legumes - while keeping red and processed meat, sugary drinks, sodium, and refined grains low.

"Since staying active and independent is a priority for both individuals and public health, research on healthy aging is essential," says co-author Marta Guasch-Ferré, a Harvard nutritionist.

"Our findings suggest that dietary patterns rich in plant-based foods, with moderate inclusion of healthy animal-based foods, may promote overall healthy aging and help shape future dietary guidelines," she adds.

While AHEI produced the strongest overall association, the researchers report it was closely trailed by other patterns, including aMED, DASH, PHDI, and MIND.

Beyond its link with overall healthy ageing, AHEI was also the most strongly associated with preserving physical function and mental health. PHDI showed the strongest association with maintaining cognitive health and with surviving to age 70.

Ultra-processed foods and the odds of ageing well

By contrast, eating more ultra-processed foods was linked with a reduced probability of healthy ageing.

"Our findings also show that there is no one-size-fits-all diet. Healthy diets can be adapted to fit individual needs and preferences," says lead author Anne-Julie Tessier, a nutritionist at the University of Montreal.

The study was published in Nature Medicine.