This one’s tricky. Yes, sun exposure can boost your D levels — just 15 minutes can give you the equivalent of 2,000 to 4,000 IU. However, doctors may discourage this because of the risk of skin cancer, which occurs more frequently in RA patients on some biologic drugs. “It’s safer and more effective to use an oral supplement,” says Dr. Hylland. That said, no need to fear the outdoors. Just wear sunscreen!