The research, based on data from more than 100,000 people spanning 30 years, revealed that people who followed a healthy diet from their 40s onward were between 43 and 84 per cent more likely to be well-functioning physically and mentally at age 70 compared with those who did not.

“People who adhered to healthy dietary patterns in midlife, especially those rich in fruits, vegetables, whole grains and healthy fats, were significantly more likely to achieve healthy ageing,” said Anne-Julie Tessier, PhD, postdoctoral fellow at Harvard TH Chan School of Public Health. “This suggests that what you eat in midlife can play a big role in how well you age.”

Tessier presented the findings this week at NUTRITION 2024, the flagship annual meeting of the American Society for Nutrition held in Chicago.

The researchers found that higher intakes of fruits, vegetables, whole grains, unsaturated fats, nuts, legumes and low-fat dairy were associated with greater odds of healthy ageing, while higher intakes of trans fat, sodium, total meats, and red and processed meats were associated with the converse.

Previous studies have shown that a healthy diet can help ward off chronic diseases, but this latest research focuses on healthy ageing – defined not just as the absence of disease but the ability to live independently and enjoy a good quality of life as we grow older. 

“Traditionally, research and derived dietary guidelines have focused on preventing chronic diseases, like heart disease,” explained Tessier. “Our study provides evidence for dietary recommendations to consider not only disease prevention but also promoting overall healthy ageing as a long-term goal.”

Researchers analysed data from more than 106,000 people going back to 1986. Participants were at least 39 years old and free of chronic diseases at the start of the study and provided information about their diet via questionnaires every four years. As of 2016, nearly half of the study participants had died and only 9.2 per cent survived to age 70 or older while maintaining freedom from chronic diseases and good physical, cognitive and mental health.

Eight healthy dietary patterns

The researchers compared rates of healthy ageing among people in the highest versus lowest quintiles, for adherence to each of eight healthy dietary patterns that have been defined by previous scientific studies. The strongest correlation was seen with the alternative healthy eating index, a pattern that reflects close adherence to the Dietary Guidelines for Americans. Participants in the top quintile for this dietary pattern were found to be 84 per cent more likely to achieve healthy ageing than those in the bottom quintile.

Strong correlations were also found for the empirical dietary index for hyperinsulinemia diet – associated with a 78-per-cent greater likelihood of healthy ageing); planetary health diet (68 per cent); alternative Mediterranean diet (67 per cent); dietary approaches to stop hypertension (DASH) diet (66 per cent); the Mediterranean-DASH intervention for neurodegenerative delay (MIND) diet (59 per cent); and empirical dietary inflammatory pattern (58%). A somewhat more modest association was found for the healthful plant-based diet (43 per cent).

“A finding that stood out was the association between the planetary health diet and healthy ageing,” reasoned Tessier. “This diet is based on the EAT Lancet Commission’s report, which emphasises fruits, vegetables, whole grains, plant proteins, and healthy fats from sustainable sources. The fact that it emerged as one of the leading dietary patterns associated with healthy ageing is particularly interesting because it supports that we can eat a diet that may benefit both our health and the planet.”

The ties between diet and healthy ageing remained strong even when the researchers accounted for physical activity and other factors known to impact health. Tessier noted that each healthy dietary pattern was linked with healthy ageing as a whole, as well as with the individual components of healthy ageing, including physical health, cognitive functioning and mental health.

Given the study’s focus on dietary patterns in middle age, Tessier said that future research could help explain the potential impacts of switching to a healthier dietary pattern later in life.