What We Learned From Harvard’s New Study on Healthy Aging

Last month, two opinion articles in The New York Times, published on consecutive days, argued that nutrition and overall health are very straightforward, based on “boring” principles we’ve known since “third grade,” like eating your vegetables. Wellness entrepreneurs who say otherwise are probably just trying to sell you their fake advice and products, according to one of the op-eds.

Phony wellness pushers make easy targets, but they’re not the only ones saying this stuff is complicated. Scientists at the world’s leading universities see great complexity in food’s interactions with human biology over a lifetime. They’re studying these dynamics, forming new hypotheses and pointing to unsettled research questions. When it comes to the dietary principles that scientists have agreed upon, few American adults, let alone third graders, are actually aware of them.

The message that healthy nutrition rests entirely on long agreed-upon, clear-cut fundamentals, as articulated by those Times editorials, is just as anti-science as the hyped-up claims of wellness gurus. A recent nutrition study, compiled by a team from Harvard and presented at the annual meeting of the American Society for Nutrition, drives home the value of complex research findings in this field — and the need to communicate them clearly.

The Study’s Main Finding

The research, presented at the ASN conference on July 2, found that people who start practicing certain dietary habits in middle age are much more likely, 30 years later, to enjoy physical and cognitive longevity without chronic diseases.

Yes, fruits and vegetables are part of that “healthy aging” equation. But no, it’s not nearly as simple as scooping them into a bowl each day.

For the study, the team of Harvard scientists, specializing in nutrition and epidemiology, assessed a database with health information on over 106,000 people going back three decades. The people who, at age 40, were regularly having fruits, vegetables, whole grains, unsaturated fats, nuts, legumes and low-fat dairy — and then maintained these habits — enjoyed much better odds of good health at age 70.

“These foods, high in fiber, healthy fats, and vitamins, may help reduce chronic inflammation, which is a major contributor to age-related decline,” says Anne-Julie Tessier, a research associate at Harvard who led the study. The healthy-aging recipe also involved less red and processed meat, total meat, trans fats and sodium.

What Most People Don’t Know

If you understand all of the food terminology used in the previous section — and grasp their implications for what you should put in your mouth — you are unique among Americans. You also probably have a higher-than-average level of education, although a fancy degree doesn’t guarantee health literacy.

A Milken Institute report from 2022 noted that 88% of Americans have “limited health literacy.” Those with an education level higher than a bachelor’s degree are more likely to have “proficient” health literacy (the highest score), compared to lower education levels, but even in this elite group that only accounts for 33% of people.

Another study found that 1 in 3 American adults has difficulty reading food labels. “It’s not easy for many people to consume medical jargon,” says Lee Sanders, a pediatrician and professor of health policy at Stanford, who studies health literacy. Terms like trans fats and carbohydrates need to be communicated more clearly, Sanders says. “But that does not mean we should oversimplify things.”

“Nutrition literacy is still quite low,” says Frank Hu, a Harvard professor who co-authored the recent study on healthy aging. “More evidence-based, science-based information is very important for the general public.”

Look Beyond the Mediterranean Diet

The Harvard study also shows that you don’t have to follow a Mediterranean diet, the one healthy diet backed by significant research that most Americans have actually heard of, Sanders says. The researchers studied the effects of seven other diets that differ in their particular food items but share similar components (like healthy carbs and plant-based proteins) to those found in typical Mediterranean foods.

Each diet, including the Mediterranean, was associated with healthier aging. Several diets, such as the one implied by the Alternative Healthy Eating Index (AHEI), actually delivered more benefits, though the differences were relatively small.

This means that if you like foods not found in the Mediterranean eating pattern — say, due to your background, upbringing or individual tastebuds — you can still eat for longevity over the years. “These findings allow for many more individual and cultural choices,” says Sanders, who was not involved in the research.

“There’s no one size fits all approach,” Tessier says.

The Right Amount of Fruits and Vegetables

The authors found that, when it comes to fruits and vegetables, how many you eat may be just as important as what you eat. People following the diet with the strongest link to longevity, related to the AHEI, had five servings per day of vegetables and 2.5 servings of fruit. These people aged more healthfully — and are more likely to still be alive! — than those who got three vegetable servings and one fruit serving per day.

So it seems the simple adage “An apple a day keeps the doctor away” is dead wrong. The right number is closer to two or three per day. That’s considerably more fruit over a lifetime. Complexity wins again.

“Fruits, including antioxidant-rich berries, appear to be particularly beneficial for healthy aging,” Tessier says, making it all the more important to get the right amount.

Meanwhile, an excess of higher-glycemic fruits such as bananas and pineapples could be worse for metabolism over the years if you have a family history of diabetes. But as Sanders notes, many Americans haven’t heard about high-glycemic foods.

“The fruits and vegetables message is simple, but the research is not that simple,” Hu says. He adds that more studies, with clear communication of the findings, are needed to help the general public, government policies, school nutrition programs and adult-care facilities appreciate and follow the important nuances — especially as the USDA continues to count French fries and pizza as vegetables.

Respect the Food Groups

The study also shows that it’s important to have plenty of foods from other healthy categories.

For example, the AHEI calls for five servings of whole grains per day for women and six for men, as opposed to refined grains. Healthy fatty acids found in certain fish and avocados should be prioritized as well.

These distinctions are far from obvious to Americans. After decades of propaganda blaming all types of fat as the culprit behind diseases, many people remain understandably confused about healthy fat. It doesn’t help that food companies continue to advertise their products as “low fat” or “fat free,” reinforcing the idea that fat is to be avoided at all costs.

“One of the key messages here is to choose more healthy fats,” Tessier says.

Yet, it’s also possible to have too much healthy fat. Sanders treated a seven-year-old boy who’d gained excess weight because his parents, from Central America, were feeding him avocados throughout the day. “Avocados are their culture,” Sanders explains, so individuals need to find the right balance for themselves based on their physiologies, cultures and health goals.

It’s Never Too Early to Start

Adherence matters. You often hear that it’s never too late to start eating healthy, and there’s some truth to that, Hu says. Yet again, though, the devil is in the details: if you start in middle age, this study shows, “the long-term effects over the decades are cumulative.”

This finding is unique from other research; the authors were able to examine a longer window of time than previous studies on healthy aging.

If you start even earlier than middle age, the benefits probably accumulate even more. If you’re in your 20s and want to think sharply and play tennis on your 70th birthday, it’s wise to adopt a healthy diet today. As Tessier puts it, “It’s never too late to make positive changes to your diet, but it’s never too early, either.”

This brings us back to health literacy: those who are knowledgeable about nutrition — a minority of Americans — are more likely to adhere to healthy diets. Sanders’s own interventions to educate people about healthy eating lead to better nutrition. This sort of communication may be especially effective when it teaches people about potential benefits, such as fewer chronic diseases later in life.

Nutrition Matters, Even If You Exercise

Of course, understanding nutrition is challenging — and especially if you’re being bombarded with fringe theories on the internet. “There’s just so much misinformation and confusion about nutrition, especially on social media,” Hu says. You will find warring ideological camps claiming that exercise is much more important than diet, and that diet is much more important than exercise.

The recent Harvard study helps people understand that what you eat is still important, even if you’re already a dedicated exerciser. Thanks to the quality of their data, the researchers could see that the link between diet and healthy aging was independent of how much people exercised. “After accounting for exercise, the healthy diets’ associations remained just as consistent and just as strong,” Tessier says. The scientists also accounted for wealth and education, BMI, smoking status, multivitamin intake, family history of various diseases, and sex. “We isolated the role of diet as much as possible,” she adds.

This doesn’t mean nutrition is more important than exercise. The researchers couldn’t compare the association with diet to the association with exercise in terms of how strongly they predict healthy aging. Suffice to say, we should be prioritizing both — and learning the details.

This Stuff Isn’t So Simple After All

“Research has long shown that health and longevity come down to five fundamental lifestyle behaviors,” one of the Times op-eds stated. “This stuff is simple, somewhat boring.” It goes on to suggest that a good longevity diet amounts to avoiding obesity.

But the Harvard research, which is currently under review for publication, shows that healthy eating involves many nuances. And that if we appreciate them, we live longer. As another Times piece recognized last week, “These are times in which we’re rethinking how we eat.”

It’s understandable to want nutrition to be simple. Life is complicated enough, and because our body’s internal machinations are invisible and mysterious, it’s tempting to pretend we’re powerless over them. If we’re genetically constrained, we’re absolved of responsibility. But research shows that our genes don’t determine health outcomes. More aspects of healthy aging are controllable through lifestyle choices. This shows the importance of embracing the nuances of nutrition, for people who can afford to do so, and governments helping everyone understand and access the right approaches.

Complexity may be a burden, but it’s also a blessing — if you hope to enjoy the next few decades without a debilitating chronic illness.