Interestingly, Vit D levels are strongly associated with the recurrence rate of Melanoma.
Oz is skin cancer capital of the world, and I don't buy the traditional line on melanoma.
Skin cancers show up where there's obvious and repeated sun damage, melanomas tend not to.
Know of 3 melanomas in people I know, and none were in traditionally sun affected areas. When the specialist was asked in one instance how the sun theory could explain a primary melanoma in a labial fold, he mumbled something about sun exposure as a child.
That being said, our children get heaps of sun, always with a hat, and have never been allowed to burn, through either timing of activities (they don't want to play in 100F heat anyway), or zinc based sunscreen as appropriate.