In northern latitudes, there is not enough sun exposure to maintain sufficient vitamin D levels in the winter season, and vitamin D supplementation is often required. (sciencedaily.com)
I also avoid sunscreen for the most part, and just get out of the sun or cover up when I have had enough sun exposure for the day. (wellnessmama.com)
Unfortunately, most people have a difficult time getting enough sun exposure to meet their vitamin D needs. (onnit.com)