Q&A: Harvard's "healthy aging" lead author

Dr. Anne-Julie Tessier on what her research says about dietary choices, life expectancy and the odds of reaching 70 in good health.

Dr. Tessier (photo: LinkedIn)

The news: Following up my recent post that examined several (otherwise unreported) elements of Harvard’s new “healthy aging” study, I requested an interview with its lead author, Anne-Julie Tessier, an assistant professor of nutrition at the University of Montreal and a visiting scientist at the Harvard T.H. Chan School of Public Health, which publicized the research.

Below are Dr. Tessier’s answers to my initial questions.

About this interview: Dr. Tessier offered to take my questions by email, instead of a phone conversation; so asking immediate follow-up questions wasn’t possible, though I hope to do so — optimally, with your feedback. Her detailed answers, in our relatively brief exchange below, nonetheless illuminate her and her co-authors’ perspectives on this massive observational study of nutritional data (all of it self-reported). You’ll also find her detailed breakdown of the Alternative Healthy Eating Index (AHEI), the specific diet that was most associated with what this Harvard study deemed "healthy aging.”

Background: The study, of 105,000 health professionals over 30 years, published last month in Nature Medicine, concluded that out of eight healthy, plant-based diets, the AHEI diet had the strongest association with reaching age 70 in good health. (The strictly vegetarian diet, by the way, had one of the weakest associations with “healthy aging,” according to the study.)

Dr. Tessier’s answers below appear unedited and in their entirety.

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My email-based interview of Dr. Ann-Julie Tessier

Dr. Tessier, only 9.3% of the longevity of the study's cohort reached age 70 in full health, which I believe the study defined as having none of 11 chronic diseases and being physically, cognitively and mentally "intact." Was that rate of "healthy aging" notable to you and your co-authors?

Anne-Julie Tessier: Yes — this is an interesting finding in itself, as 9.3% is quite low. Indeed, we included 11 chronic diseases in our definition of healthy aging, which is strict, and few people lived to the age of 70, 75 without any of these. These include, cancer, diabetes, stroke, kidney failure, pulmonary diseases, and many others. Still, the observed rate is within the expected range based on previous data life expectancy and chronic disease rates.

About 38% of the 105,000 people in this study lived to age 70, even though what is known as cohort-based life expectancy for this group was significantly greater than 70. How should the public understand what appears to be a relatively low survival rate, given cohort life expectancy for this population was 73 and 78 for men and women, respectively?

Dr. Tessier: In this study, we cannot conclude that the life expectancy is low per se given that many are still living, and we do not have the full lifespan data. Also, we excluded individuals who were below age 40 at baseline for all participants to get a chance of achieving 70 years in 2016. The 38% needs to be interpreted in this context.

I'd like to give readers a sense of what the AHEI diet, specifically, includes and comprises and what it doesn't: What amounts of unprocessed animal protein (red, poultry, fish, eggs) did that diet include? Did it also include a significant amount of processed meat?

Dr. Tessier: Having a high Alternative Healthy Eating Index score would translate into eating 5 servings per day of vegetables, and having an extra serving of green leafy vegetables, 4 servings per day of fruits, 5-6 servings per day of whole grains, a serving per day of plant protein such as nuts or legumes, a serving of fish weekly and using plant oils as the main culinary fat.

Maximum scoring was given when no red/processed meat was consumed and 0 points were attributed when more than 1.5 serving was consumed. Poultry, fish and eggs were not included in the scoring. Only n-3 PUFAs were attributed positive scoring.

Ref for scoring: https://www.sciencedirect.com/science/article/pii/S0022316622027894?via%3Dihub

The purely vegetarian diet came as the weakest association to "healthy aging," according to your study. Can you explain why that may be?

The healthy dietary patterns we examined share common principles, such as being rich in vegetables, fruits, whole grains, and healthy fats. However, as we age, our needs for certain nutrients—particularly protein and vitamin B12—increase. This may explain why including some nutrient-dense animal-based foods, such as fish or yogurt, could offer additional benefits for healthy aging.

How should readers contextualize the findings in this research of diet and health of only health professionals? Would this cohort have had an easier or more difficult time remaining healthy vs. people in other professions?

Dr. Tessier: Health professionals may have an easier time remaining healthy compared to other populations. This is why replicating the analysis in populations with diverse socioeconomic backgrounds and ancestries will offer valuable insights into the generalizability of our results.

How did exercise and any potential night-shift work schedules correlate to healthy aging among this cohort of health professionals? (I assume the exercise questions were part of the "booklet" questionnaires between 1996 and 2012 only, but please correct me if that's not accurate.)

Dr. Tessier: Exercise and night-shift work schedules were not the primary exposure of this study, therefore I cannot speak to these. However, some previous studies have been published: https://pubmed.ncbi.nlm.nih.gov/35507343/

Which of your research's results surprised you and your team?

Dr. Tessier: We were surprised by the strength of the associations between healthy eating patterns in midlife and healthy aging, even after accounting for other key factors like physical activity, which also impact health. Interestingly, all the healthy diets we studied were linked not only to overall healthy aging but also to its individual domains, including cognitive, physical, and mental health.

Also, a novel finding was the association between the planetary health diet and healthy aging. This diet, which minimizes animal products and emphasizes fruits, vegetables, whole grains, and healthy fats, emerged as one of the leading dietary patterns associated with healthy aging. This is particularly interesting because it suggests that we can eat a diet that benefits both human health and environmental sustainability.