With every sip of wine, bite into an apple, teaspoon of olive oil or taste of dark chocolate, you’re consuming a dose of polyphenols, naturally occurring antioxidants found in plant-based foods. Antioxidants protect the body from free radicals, which are natural byproducts of energy production. Free radicals perform important jobs throughout the body, but in excess, they can harm healthy cells and promote inflammation. Therefore, free radicals must be tightly controlled by our body’s natural antioxidant system, which is supported by a healthy diet and lifestyle. Population studies have linked a diet rich in polyphenols with a reduced risk for heart disease, cancer, obesity and diabetes among other diseases associated with inflammation. Yet, when it came to producing solid evidence that polyphenols could extend life, researchers came up cold — until now.

First, a bit of history: Most studies on diet rely on self-reported questionnaires, which means that participants must be both honest and accurate. Of course, we know that self-tracking is notoriously inaccurate, especially when it comes to maintaining food diaries. (A Dose of Reality)

Self-reported studies have failed to show a connection between eating more polyphenols and living longer. But a more precise way of tracking polyphenols — using a biomarker found in urine (total urinary polyphenol concentration or TUC) — has produced different results. A recent article published in the Journal of Nutrition, reported on a 12 year follow-up study of 807 Tuscan men and women aged 65 and over living in the Chianti region of Italy. Researchers found that study participants with the highest levels of TUC (polyphenols in their urine) at the inception of the study showed a 30% reduction in mortality.

What’s remarkable is that, for the first time, researchers had produced hard evidence based on laboratory data that people who consumed the most polyphenols were living longer than those who consumed the fewest. Notably, when researchers contrasted this finding with the self-reported diet questionnaires the participants filled out at the beginning of the study, they did not find a correlation between polyphenol intake and longevity.

It’s no coincidence that the Mediterranean Diet, which has been deemed one of the healthiest cuisines in the world, is abundant in plant foods that have high levels of polyphenols. As these researchers note, “Indeed, comparable results have also been reported when the link between mortality and a greater adherence to a Mediterranean diet, which is a dietary pattern rich in fruits, vegetables, and nuts, was evaluated.”

Want to get more polyphenols into your life? Eating a wide variety of brightly colored fruits, vegetables and whole grains is a good way to load up on these healthy phytochemicals. Olive oil, a staple of Mediterranean cuisine, is also rich in polyphenols.