NO DOUBT you’ve heard the Mediterranean diet is good for you. Scientists have been fascinated by the region’s traditional way of eating since at least the 1960s, when they connected it to better health and longevity. And in the past half-century, the science has not been static: Researchers are constantly making discoveries about this ancient diet, from its ability to boost good gut bacteria to its association with lower inflammation and less insulin resistance. That helps explain why—despite