Vitamin D is an essential vitamin for human health. Produced naturally by the body, and supplied in certain fortified foods, Vitamin D is a key compound enabling the body to regulate calcium absorption and incorporate dietary calcium into bones and teeth. The D3 variant of the vitamin is generally considered superior to D2. Pasteurized milk is the leading dietary source of vitamin D3, and the vitamin's presence has helped eliminate certain childhood diseases.
Vitamin D in the Human Body
The human body naturally produces vitamin D upon receiving adequate sunlight exposure -- about 15 to 30 minutes of sunlight several times weekly. Because many people don't receive adequate regular sunlight, dietary sources of vitamin D are often important to maintain sufficient levels of the vitamin in the body. Accordingly, vitamin D is added to a number of foods in the United States, including almost all pasteurized milk.
Vitamin D2 and D3
Formally known as cholecalciferol, vitamin D3 is the variant of vitamin D naturally produced by the human body, as well as certain animals. It is also the form of vitamin D added to most fortified milk products. Synthetic vitamin D3 can also be produced in laboratories and is chemically identical to the natural form. An alternative form of the vitamin, D2, is produced naturally in plants and can also be chemically synthesized. Data analyzed in the "American Journal of Clinical Nutrition" indicate that D2 is an inferior form of vitamin D, and its use should be discouraged in favor of vitamin D3.
Vitamin D Requirements and Sources
Dietary guidelines published by the Institute of Medicine of The National Academies mandate 400 IU of daily vitamin D for newborns up to 1 year of age. From ages 1 to 70 years, healthy individuals should receive 600 daily IU, followed by 800 IU daily from age 70 and up. People with vitamin D deficiency or other health needs may require more vitamin D, while people who enjoy frequent sun exposure or have a diet high in certain fish species may need less from other food sources.
Vitamin D in Milk
Aside from natural body production, the most important vitamin D source in the United States is pasteurized milk. According to the U.S. National Institutes of Health, a single 8-oz. serving of pasteurized milk contains 30 percent of vitamin D's recommended daily intake. Pasteurized milk has been fortified with vitamin D since the 1930s in an effort to combat rickets, a disease of bone weakening and malformation caused by the body's inability to absorb calcium. Fortified milk today is credited with virtually eradicating rickets in the United States, and its vitamin D content supports bone and tooth health throughout life.
Absence of Vitamin D in Raw Milk
Vitamin D is only added to pasteurized milk but is not part of raw milk. Raw milk is bottled shortly after milking, without germ-killing pasteurization or the addition of vitamins. Raw milk poses health risks because of its higher likelihood of causing bacterial infections, and it lacks the vitamin D that is crucial to bone development and strength. Most food safety and medical experts strongly advise against drinking raw milk.
References
- National Institutes of Health: Dietary Supplement Fact Sheet; Vitamin D
- U.S. FDA: Vitamin Fortification of Fluid Milk Products
- "American Journal of Clinical Nutrition": The Case Against Ergocalciferol (Vitamin D2) as a Vitamin Supplement; Lisa Houghton, et al.; 2006
- U.S. FDA: The Dangers of Raw Milk
- "Vitamin D and Milk"; Dr. Anthony Norman, University of California, Riverside; December 2000
- Harvard School of Public Health; Vitamin D and Chronic Disease; Dr. Edward Giovannucci
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