There are very few significant dietary sources of vitamin D. Its natural distribution is limited to small amounts in fish, oils, ghee, butter and egg yolk. Compared to fish-liver oil, which is the best source of vitamin D, other foods are quite low in the vitamin. Ideally, a diet that includes dairy, fish and egg yolk, coupled with adequate exposure to sunshine, should prevent Vitamin D deficiency.
In the absence of adequate exposure to sunlight and poor availability of vitamin D fortified foods, supplements are necessary; however, excessive vitamin D can be toxic and must be taken under careful supervision of a physician. Most experts agree that the minimum daily intake of vitamin D should be at least 800-1000 I.U. (International units).