Vitamin D (cholecalciferol) is essential for humans, but can be made in our skin under the influence of ultraviolet light from the sun. Thus we need not always obtain vitamin D from the diet.

People who are mainly dependent on dietary vitamin D, which is fat-soluble, may be deficient in the

vitamin, since poor absorption of vitamin D can occur because of poor fat absorption. Also, for the full action of vitamin D it must be further metabolized in liver and kidney, which means that disorders of these organs can lead to vitamin D deficiency.

The main function of vitamin D in humans is to regulate calcium and phosphorus metabolism. Its deficiency in children leads to rickets and in adults to osteomalacia, both of which are disorders of bone. As little as 2.5 micrograms (100 international units) of vitamin D per day will prevent rickets, but 10 micrograms (400 international units) per day is usually recommended for children, in case there is inadequate sunlight, or they have dark skin (which hinders absorption of ultraviolet light through their skin), or both.

VITAMIN D INTAKE

FIGURE 50: THE VITAMIN D CONTENT OF SOME FOODS

FOOD	VITAMIN D   (micrograms per 100 grams of food)
Cod liver oil Fish (salmon, sardines, tuna) Margarine Eggs Butter Cheese	200-700 5-12 5-6 1-2 4-1.2 .1-.3
Milk, meat, fruit and vegetables are not significant sources of this vitamin.

	Fat-Soluble Vitamins
	-	Vitamin A
	-	Provitamin A (beta-carotine)
		Vitamin D
	-	Vitamin E
	-	Vitamin K

Also on this page:
-  Vitamin D intake
-  Figure 50: Vitamin D
   content in some foods