Harvard study finds their isn’t a ‘perfect diet’ for healthy aging

By Stephen Beech

Eating a healthy diet in middle age is key to aging well, according to new research.

Sticking to mostly plant-based foods and eating little meat or processed products from the age of 40 means you are less likely to develop a serious illness by the age of 70, say scientists.

Healthy aging was defined as reaching 70 years old free of major chronic diseases, with cognitive, physical, and mental health maintained for the 30-year study of food habits among more than 105,000 middle-aged adults.

The study - by researchers at Harvard T.H. Chan School of Public Health in Boston, the University of Copenhagen in Denmark, and the University of Montreal in Canada - is among the first to examine multiple dietary patterns in midlife in relation to overall healthy aging.

All eight dietary patterns studied were associated with healthy aging, suggesting that there is no "one-size-fits-all" healthy diet.

The study, published in the journal Nature Medicine, is among the first to examine dietary patterns in relation to overall healthy aging, rather than in relation to specific diseases or mortality.

The research team found that, overall, maintaining a healthy diet rich in plant-based foods, with low to moderate intake of healthy animal-based foods and la ower intake of ultra-processed foods, was linked to a higher likelihood of aging well.

Study co-corresponding author Professor Frank Hu, chair of the Department of Nutrition at Harvard Chan School, said: “Studies have previously investigated dietary patterns in the context of specific diseases or how long people live.

"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?”

The research team used figures from the Nurses’ Health Study and the Health Professionals Follow-Up Study to examine the midlife diets and eventual health outcomes of more than 105,000 women and men ages 39 to 69 over the course of 30 years.

Participants regularly completed dietary questionnaires, which the researchers scored on how well participants adhered to eight healthy dietary patterns.

They 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).

Each of the diets emphasizes a high intake of fruits, veg, whole grains, unsaturated fats, nuts, and legumes, and some also include low to moderate intake of healthy animal-based foods such as fish and certain dairy products.

The researchers also assessed participants’ intake of ultra-processed foods - such as ham, sausages, burgers, ice cream, crisps and breakfast cereals - which often contain artificial ingredients, added sugars, sodium, and unhealthy fats.

The study found that 9,771 participants - 9.3% of the participants - aged healthfully.

Adhering to any one of the healthy dietary patterns was linked to overall healthy aging and its individual domains, including cognitive, physical, and mental health.

The leading healthy diet was the AHEI, which was developed to prevent chronic diseases.

Participants in the highest quintile of the AHEI score had an 86% greater likelihood of healthy aging at 70 and a 2.2-fold higher likelihood of healthy aging at 75 compared to those in the lowest quintile of the AHEI score.

The research team said that the AHEI diet reflects a diet rich in fruits, vegetables, whole grains, nuts, legumes, and healthy fats and low in red and processed meats, sugar-sweetened drinks, sodium, and refined grains.

Another leading diet for healthy aging was the PHDI, which considers both human and environmental health by emphasizing plant-based foods and minimizing animal-based foods.

But higher intake of ultra-processed foods - especially processed meat and sugary and diet drinks- was associated with lower chances of healthy aging.

Co-corresponding author Professor Marta Guasch-Ferré, of the University of Copenhagen and Harvard Chan School, said: “Since staying active and independent is a priority for both individuals and public health, research on healthy aging is essential.

“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.”

Lead author Dr. Anne-Julie Tessier, of the University of Montreal and a visiting scientist at Harvard Chan School, added: “Our findings also show that there is no one-size-fits-all diet.

"Healthy diets can be adapted to fit individual needs and preferences."

The research team said the study had some limitations, notably that the participants were exclusively health professionals, so replicating it among different socio-economic groups would offer further insights.