Vitamin D is well established as essential to maintaining bone strength. However, a growing number of animal and human studies evidence an important link in vitamin D deficiencies and certain cancers and immune system dysfunction. Vitamin D deficiencies may increase the risk of prostate cancer, colon cancer, cancers of the digestive tract, type 1 diabetes, and multiple sclerosis. It has nutrition experts wondering if we are getting enough Vitamin D, and urging the FDA to increase the recommended dose from 400 IU to 800 IU. For some individuals, even this recommended increase may not be enough. Some experts are recommending 1,000 to 2,000 IU daily--from the sun, diet, and supplements.
Vitamin D is also known as the "Sunshine Vitamin." It is made by the skin when exposed to sunlight, the most potent source of Vitamin D. People in northern climates or who do not go outdoors much may not be getting enough. According to researchers in Norway, moderate sun exposure may have more beneficial than adverse health effects. Taking a 15 minutes walk with face, neck, and arms exposed in the winter and a 30 minute walk without sunscreen in the summer will increase your Vitamin D levels. Dietary sources include fortified milk and fatty fish, but to ensure daily requirements are met, the diet should be supplemented with at least 800 IU daily.
Sources:
"Vitamin D: How Much Is Enough?," Harvard Public Health Review, Spring/Summer 2007. "Addressing the health benefits and risks, involving vitamin D or skin cancer, of increased sun exposure," Proceedings of the National Academy of Sciences of the United States of America, January 15, 2008, Vol. 105, No. 2, 668-673.