Ask Dr. Dairy: What Type of Vitamin D Is in Milk?
Most milk sold at retail in the U.S. contains vitamin D. Because few foods naturally contain vitamin D, it can be added in specified amounts to foods like milk, yogurt and many cheeses to help people meet dietary recommendations.
Vitamin D fortified milk must contain at least 100 International Units (IU) and up to a maximum of 150 IU vitamin D per eight-ounce serving per national milk standards.
There are two types of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is a plant source of vitamin D; for example, it is naturally found in mushrooms. Vitamin D3 is produced naturally by the skin when exposed to ultraviolet light. Food sources that contain vitamin D3 include fatty fish (e.g., salmon, tuna, mackerel), fish liver oils and egg yolk. Vitamin D3 can also be made from lanolin. Most milk is fortified with vitamin D3.
Many categories of foods are permitted to include up to a specified amount of vitamin D. The Nutrition Facts label will tell you the amount of vitamin D in the food and the ingredient list on a food label will tell you the type of vitamin D that has been added to the food.
Over the years, there have been conflicting views in scientific literature as to whether D2 and D3 are equally effective at increasing and maintaining blood levels of vitamin D. The National Institutes of Health Office of Dietary Supplements states that no firm conclusions can be drawn about the different effects of vitamin D2 and D3.
The research in this area is still emerging. For example, a recent randomized, double-blind study among Asian and European women (20 to 64 years old) living in the UK found that eating biscuits or juice fortified with 600 IU vitamin D3 (the recommended amount for most adults) was more effective at raising blood levels of vitamin D as the same foods fortified with vitamin D2. According to the NIH, “it appears that at nutritional doses vitamins D2 and D3 are equivalent, but at high doses vitamin D2 is less potent.”
Fluid milk in the U.S. has been fortified with vitamin D since the 1930s and has been credited with making rickets a rare disease in children, which underscores why vitamin D fortification is still relevant today. Low consumption of vitamin D from foods and limited sunlight exposure has prompted the 2015 Dietary Guidelines for Americans to identify vitamin D as a nutrient of public health concern, along with calcium, potassium and fiber.
Vitamin D is important, along with calcium, for keeping bones healthy. Eating vitamin D-fortified foods, like milk, orange juice and breakfast cereals (check the Nutrition Facts label), as well as natural sources like fatty fish, can help people achieve the recommended amount of vitamin D needed for good health. For more information about vitamin D, check out these fact sheets for health professionals and the public.