New Harvard University research reveals diet for health, longevity

A 30-year study found that a diet rich in plants and low in ultra-processed foods significantly increased the likelihood of healthy aging, with AHEI and PHDI providing the most benefit.

According to a new study conducted by scientists from Harvard University, the University of Copenhagen and the University of Montreal, a diet that focuses on plant-based foods, incorporates moderate amounts of healthy animal foods and limits ultra-processed foods is associated with a higher likelihood of 'healthy aging'.

'Healthy aging' is defined as living to at least age 70 without major chronic diseases, while maintaining cognitive, physical, and mental health. This is one of the first studies to evaluate the link between midlife diet and overall aging.

" Previous studies have focused on diet in the context of specific diseases or longevity. Our study takes a multidimensional approach, answering the question: How does diet affect the ability to live independently and quality of life in old age? " – Professor Frank Hu, co-author of the study from Harvard University, shared.

Research methods and diets

The researchers analyzed data from 105,000 people (aged 39–69) over 30 years, based on two large studies: the Nurses' Health Study and the Health Professionals Follow-Up Study. Participants completed periodic dietary questionnaires, which assessed eight eating patterns:

1. AHEI (Alternative Healthy Eating Index)
2. aMED (Alternative Mediterranean Index)
3. DASH (Dietary Approaches to Stop Hypertension)
4. MIND (Mediterranean and DASH Diet to Delay Neurological Decline)
5. hPDI (Healthy Plant-Based Diet)
6. PHDI (Planetary Health Diet)
7. EDIP (Experimental Inflammatory Diet)
8. EDIH (Experimental Dietary Insulin Induced Index)

These diets all emphasize fruits, vegetables, whole grains, unsaturated fats, nuts and legumes. Some also include small to moderate amounts of healthy animal foods like fish and dairy products. Additionally, the researchers assessed consumption of ultra-processed foods – which often contain additives, sugar, salt and unhealthy fats.

Outstanding results

The study found that 9,771 people (9.3%) achieved healthy aging. Additionally, adherence to any of the above healthy diets was associated with good aging, including cognitive, physical, and mental health.

AHEI (focus on chronic disease prevention) leads: The group with the highest AHEI score was 86% more likely to age 70 and 2.2 times more likely to age 75 than the group with the lowest score.
PHDI (combining human and environmental health) also stood out, favoring plant foods and limiting animal foods.
Conversely, high consumption of ultra-processed foods (especially processed meats and sugary drinks) significantly reduced the chances of healthy aging.

Professor Marta Guasch-Ferré (University of Copenhagen) emphasized: " Our findings suggest that a plant-rich diet, incorporating moderate amounts of healthy animal meat, can promote healthy aging and guide future nutritional recommendations ."

" Research also shows that there is no one-size-fits-all diet. A healthy diet can be tailored to individual needs and preferences, " added Dr. Anne-Julie Tessier (University of Montreal).

The study's primary focus was on health professionals. The researchers say further research is needed to include a more socioeconomically and racially diverse population to confirm the generalizability of the results.

Jessica Tanner

Update 26 May 2025