Vitamin D was first named in 1922 by researchers who discovered that ultraviolet light could activate a fat-soluble substance that played an important role in bone growth. By 1925, it was suspected that a cholesterol derivative in skin was activated by sunlight. In 1931, Vitamin D2 was synthesized, and the structure of Vitamin D was established in 1936.

The main function of Vitamin D is regulating calcium and phosphorus to make bones strong. Vitamin D is necessary in the diet only for people who get too little sun to make their own Vitamin D. Vitamin D occurs naturally in a very small amount of foods.

How much sunlight is enough? The darker the skin pigment, the more exposure needed. A general rule of thumb is 2-3 hours twice a week for dark-skinned individuals and 15-30 minutes twice a week for those who are light-skinned.

Your Vitamin D Intake

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Your Top Vitamin D Sources

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Below are the major contributors of Vitamin D to your diet. This list is based upon the foods you eat the most, not the amount of Vitamin D per serving (which is shown for reference purposes only).