Are you getting enough UV light?
People should get out into the sun instead relying on supplements experts say. During the Winter months or specifically between the months of October and March, the sun is too weak to make Vitamin D with sun exposure. The lack of sunlight leaves many of us deficient in the hormone and susceptible to illness, disease and depression. Whilst there are supplements claiming to provide the amount of Vitamin D necessary to maintain levels during the winter months, the best source of Vitamin D on the planet is UV light.
Here is the full article as written in the Daily Mail.