An article, linked below, claims links between low levels of Vitamin D and worse cases of Prostate Cancer.
It suggests that sunshine is the best way to get Vitamin D and next best are supplements. Vitamin D3 is the one most like the natural version, rather than D2 which is a vegetarian option. Some foods contain Vitamin D but it's hard to get enough that way.
So you need to protect against sunburn and it suggests it takes half as long as burning to get enough Vitamin D, say bare arms and legs every day for up to 15* minutes at midday in summer in the UK, but all year for just 5* minutes in the tropics.
*Skin types react differently to the sun and there is a table describing effects.
D3 vitamin tablets are available in Boots for £5.40, is it worth a go?
I've been quite strong on using suncream as I've had skin cancer. I'm also concerned in case taking supplements actually has an opposite effect.