Vitamin D3 becomes an important nutritional factor in the absence of sunlight. In addition to geographical and seasonal factors, UV light from the sun may be blocked by factors such as air pollution, clothing, and sunscreens.

Food sources of vitamin D

Most foods don’t have much Vitamin D.
Among food sources of vitamin D are a few fatty fish such as salmon, sardines, and mackerel. Some fish liver oils have high vitamin D content, but that is not the healthiest choice for vitamin D supplementation. Vitamin D is added to the feed of some laying hens to produce eggs with vitamin D. Some cereals, breads, and orange juices are fortified with vitamin D.
The best source of vitamin D is also fortified milk. In the United States milk is fortified with the addition of 400 IU of vitamin D2 to each quart. It’s the reason rickets has practically disappeared.
But there is no Vitamin D in most milk food. Cheese, yogurt, cottage cheese, and other dairy products aren’t made with fortified milk, so they don’t have much or even any Vitamin D.
Also, raw milk, most organic milk, and goat’s milk don’t have added Vitamin D. Margarine fortified with Vitamin D is also good source of vitamin D.