Stop right there. No one likes a nutritional nag—plus, it’s not a persuasive approach to helping someone else help herself. Instead, check out these sneaky ways to spread some good health:  Take the professorial approach. Bring up a recent nutritional study you read, suggests Susan Shapiro, PhD, a registered dietitian based in Los Angeles. Saying you were shocked to learn how many teaspoons of sugar lurk in a can of soda (10!) is a polite but powerful way to help a friend. “It’s more about trying to find a nice way of sharing the knowledge, rather than saying, ‘You’re really stupid for eating this food,’” she says. Share something. Cooking for your friend is a great way to hold her nutritionally hostage: Your pal is bound to try every nutrient-packed thing on her plate—if only because she’ll want to be polite. Introducing new foods is key to getting kids to eat their veggies, says Ellyn Satter, author of Secrets Of Feeding A Healthy Family. And what are adults if not big babies when it comes to trying new things?  Foods To Boost Your Mood   Get stealthy. “Nobody wants nutrition information shoved down their throat when they haven’t asked for it,” says Dr. Shapiro. Even as a dietitian, she never doles out unsolicited advice. But she’s great at slipping knowledge, undetected, into polite conversation. During our interview, Shapiro even changed the way this writer eats oranges, casually mentioning that the white part I throw away is where all the fiber hides.  Be supportive. If your friend has a real problem with food—we’re talking six sodas a day or a weight of more than 300 pounds—express your concern, not criticism. “People feel embarrassed,” Dr. Shapiro says. “Saying you’re concerned is a much nicer way of coming across to someone.”    Also see: 8 Friends Every Woman Needs, 6 Diet Mistakes That Make You Fat, 26  Best Packaged Foods