"You're positively glowing!" is a compliment some women rank up there with, "Have you lost weight?!" Radiant, healthy skin is on nearly every woman's beauty wish list. But you don't need expensive creams or age-defying lotions to keep your skin looking youthful — your diet actually has a big effect on keeping your skin healthy. Read on to find out what causes that youthful glow to fade as you age, and the six nutrients that can help bring it back.