COVER The millennials may be onto something. Their favored avocado toast features a mixture of healthy fats, seeds, and grains recommended by nutrition experts in a consensus reading of available scientific studies. This special issue explores what we know—and what we need to learn—about defining a healthy diet that can sustain a strong body and protect against age-associated diseases. See page 762.

Photo: Scott Suchman; Styling: Nichole Bryant