Like other vitamins, vitamin D is a substance needed for health but only in tiny amounts. Unlike other vitamins, it doesn't occur naturally in food but can be made in the body. Most people know that humans use sunlight to make vitamin D, the "sunshine vitamin." But modern humans don't get much sunlight, so we end up at the vitamin counter, often confused about what to buy.

Our bodies make vitamin D3, cholecalciferol. At the supplement counter, you can choose from D3 or D2. Vitamin D2 is ergocalciferol, which differs slightly from D3 but behaves the same way in the body. D3 is slightly more potent.聽

The main difference between the two supplements is how they are made. D3 comes from animal sources, although it can be made from lichen. D2 is derived from plant sources. If you are a vegan or vegetarian, you'll want to read labels closely.聽

Vitamin D is fat-soluble (absorbed along with fats), but taking it with oily foods isn't necessary. You can also get vitamin D from food. In the United States, many foods such as soy, almond, and oat milk are fortified with vitamin D. Few foods in their natural state contain vitamin D.

Authorities disagree about how much vitamin D the body needs. In the United States, the Daily Value (DV) for vitamin D has been set at 800 International Units (IU).聽

It's important not to take too much vitamin D. Vitamin D toxicity is rare but can be serious, resulting in symptoms ranging from nausea to bone pain and kidney stones.

聽A deficiency of vitamin D can have serious consequences in the body. Vitamin D is vital for these reasons:

1. 聽Bone Health

Doctors discovered vitamin D when they were studying rickets, a children's bone disorder. Today rickets is rare, but vitamin D is still needed for bone health. It's especially important for women past menopause, who are at risk of osteoporosis. Vitamin D is also used to treat a more serious bone condition called osteomalacia (softening of bones). Vitamin D allows the body to absorb calcium. Without vitamin D, the body uses only a small percentage of the calcium in food.