Outside the tropics UVR has to penetrate through a thicker layer of atmosphere, which results in most of the UVB reflected or destroyed en route; because of this there is less potential for vitamin D biosynthesis in regions far from the equator. Higher amount of vitamin D intake for dark-skinned people living in regions with low levels of sunlight are advised by doctors to follow vitamin D rich diet or take vitamin D supplements,[22][79][80][81][82][83] although there is recent evidence that dark-skinned individuals are able to process vitamin D more efficiently than lighter-skinned individuals so may have a lower threshold of sufficiency.[22]