evidence: Sunscreen is essential for protecting your skin from early aging and skin cancers, which often are a direct result of the sun's ultraviolet, or UV, radiation. Even with increased awareness of dangers from the sun, more people in the U.S. are diagnosed with skin cancer each year than all other cancers combined. By age 70, at least 1 in 5 people in the U.S. will develop skin cancer. [...] Fact: Even well-applied sunscreen lets 2% to 3% of the sun's ultraviolet B rays reach your skin, and your body needs only a little to produce vitamin D. Rather than risk skin cancer, it's better to seek your vitamin D needs through a healthy diet or supplement.