Why is Vitamin D Added to Milk?

If you’ve ever looked closely at your milk’s label, you may have noticed that vitamin D is added to milk. Why is vitamin D added to milk, you may ask? The story behind vitamin D and milk actually goes back to the early 20th century.

In the 1900s, rickets, a childhood bone disorder caused by not getting enough vitamin D, impacted a good number of children. In fact, around 80 percent of children in Boston had rickets at that point in history.

Around that same time, scientists began to understand the roles milk’s nutrients play in the body. For example, they learned that milk’s minerals, specifically calcium and phosphorus, were key to bone and teeth development.

In 1922, Dr. E. V. McCollum discovered that vitamin D could prevent rickets, because it was needed to help the calcium to get absorbed, so there was a scramble to get vitamin D into the diets of American children. Because vitamin D is not prevalent in many foods, fortifying milk with additional vitamin D was a natural solution, since it also contained key minerals for bone development.

Vitamin-fortified milk began to appear in the 1920s and became more common by the 1930s. Today the milk found in your supermarket is fortified with vitamin D, which has played a role in making rickets now a rare disease in the United States.