10 Reasons You're Healthier Than You Think

5. You take your lunch hour.

It might seem virtuous to scarf down a sandwich in front of your computer every day, but a 15- or 20-minute break outdoors is a much smarter move. The sunlight can boost your mood, making you more productive for the rest of the afternoon, and it may also help prevent disease. A review of studies published in the American Journal of Public Health found that getting sufficient vitamin D significantly reduced the risk of developing colon, breast, prostate, and ovarian cancers. Fifteen to 20 minutes of daily sun exposure helps your body manufacture vitamin D, which can boost your immune system. Just don't go more than 20 minutes unprotected, as that increases the risk of skin cancer and sun damage. If you live north of Washington, D.C., however, you're probably not getting enough sun to produce vitamin D from November to March. Make up for it by taking a multivitamin that has at least 200 IU daily; and also load up on D-rich salmon and fortified milk and orange juice.

Top That: Spend your time outside strolling, not sitting. In a Harvard Medical School study, women who walked about a half an hour a day reduced their risk of heart disease by 35 percent.