There may be no fountain of youth, but a diet rich in plant foods might be one of the keys to thriving later in life, a large 30-year study suggests.

The study, by researchers at Harvard University, identified eating habits in middle age that seem to boost the chances of “healthy aging”—defined as making it to at least age 70 free of major chronic diseases and mentally sharp. Several different diets were linked to such success, but they all have some essentials in common: They emphasize plant-based foods such as vegetables, beans, nuts, and whole grains, and limit red meat, sugar, and highly processed foods.

That might sound like old news to anyone who follows the latest on nutrition research. It’s true that plant-rich (or “plant-forward”) diets have long been tied to lower risks of specific health conditions, like heart disease and certain cancers, as well as a longer lifespan.

But the new study, published in Nature Medicine in March, adds a layer by asking a broader question: Can plant-rich diets help people not only live longer but do so in optimal health?

To get an answer, the Harvard team turned to data from two studies of over 100,000 medical professionals whose health and lifestyle habits have been tracked for up to 30 years. The researchers focused on participants’ long-term adherence (starting in middle age) to any of eight different diet patterns that are considered generally healthy—including the famous Mediterranean diet and the DASH diet, which was developed for improving blood pressure. While the specifics of the different eating patterns vary, they all prioritize plant-based foods, healthy fats, and restrictions on added sugars, salt, and animal products high in saturated fat.

Overall, the study found, participants who stuck with any of those healthy eating patterns increased their chances of reaching their 70s in great shape. Specifically, a diet pattern dubbed the Alternative Healthy Eating Index came out on top. Participants who were in the top 20 percent for adherence to that eating style were about twice as likely to be free of chronic diseases and problems with memory and thinking at age 70 or 75, versus their counterparts who were least adherent.

To be clear, the findings do not suggest there’s a magic diet for maintaining your vim and vigor into your 70s and beyond. Even in this group of healthcare professionals, only 9 percent met requirements for the study definition of “healthy aging”—a sign that it’s a difficult feat to achieve. Plus, diet is certainly not the only factor that matters when it comes to aging well: There’s genetics, which obviously can’t be changed, as well as environmental influences like exercise, smoking and drinking habits, and exposure to chronic stress (to name just a few).

That said, of the factors we can potentially change, diet is a big one. And following certain principles around eating likely supports healthy aging:

• At any meal, allot the most space on your plate to plant foods such as vegetables and fruits, legumes (beans, lentils, peas), nuts and nut butters, soy-based proteins like tofu and tempeh, and whole grains, including brown rice, bulgur (cracked wheat), and oatmeal.
• Choose sources of “good,” unsaturated fat, including olive oil and fatty fish such as salmon, mackerel, and herring.
• Plant-based/plant-forward is not synonymous with vegetarian or vegan. You don’t have to cut animal foods out entirely. Just go easy on the burgers, steaks, deli meats, butter, cream, and ice cream (to keep your saturated fat intake in check).
• As much as possible, limit highly processed foods, such as flavored chips and other packaged snacks, frozen meals, canned soups, and sweetened breakfast cereals. In general, beware of prepared products with a long list of ingredients that don’t sound like food. They’re often low in nutrients but loaded with added sugars, sodium, and preservatives.

In many ways, this study throws weight behind the things we’ve already known about a healthy diet. But it also underscores the fact that good nutrition may not only lower the risk of disease and give you more years of life. It may also give you more time in good health, which ultimately is the best goal.