People originating from hotter regions, over countless generations were getting too much sunshine. Since sunshine destroys the folic acid, causes skin cancer and increases the rate of birth defects, the countermeasures such as darker skin were developed.
Dark skin skin blocks the harmful UVA rays, however also prevents vitamin D creation. The dark-skinned people living in the northern climates may not be getting enough sun.
Similarly, northern Europeans were not getting enough sunrays to manufacture enough vitamin D.
Evolutionary mechanism to ensure generation of vitamin D was to kick cholesterol generation into a high gear. Cholesterol is used in body's production of vitamin D.
Modern people spend much less time outside and are protecting their skin from sun with UVA blockers, therefore the cholesterol goes unused, especially in winter.
The "civilization" is trying to fix the vitamin D deficit with fortified milk, but we got stuck with extra chrolesterol.
I am not advising you to go and sun tan, but you should consider spending more time outside if your cholesterol levels are high.
Note that ocean fish-eating populations in northern climates have their diet full of naturally occurring vitamin D.
