Are You Vitamin D Deficient?

Dear Dr. Mirkin: How can I tell if I am getting enough vitamin D? More North Americans are deficient in vitamin D than any other vitamin except B12. Vitamin D deficiency can cause osteoporosis, impair immunity and cause a variety of other health problems. Most people do not meet their requirements for vitamin D with food; they get it from sunlight. If you have fair skin, exposing a few of inches of skin to sunlight for ten minutes a day provides all the vitamin D you need. Darker skins require more time or more exposed skin. Food sources of vitamin D include fatty fish, eggs, liver, vitamin D-fortified milk and butter, but concern about heart attacks has caused many North Americans to reduce their intake of these foods. At the same time, changing lifestyles and concern about skin cancer has caused many people to reduce their exposure to sunlight. Many senior citizens develop vitamin D deficiency because they do not go outdoors at all. Vitamin D is necessary to keep bones strong. One third of the people who develop hip fractures lack vitamin D. To find out if you are deficient in vitamin D, ask your doctor to draw a blood test for 24 hydroxy vitamin D. If you have low levels, you need more vitamin D. You can take a supplement that contains 400 international units of vitamin D; or get more exposure to sunlight unimpeded by glass. Drinking vitamin D-fortified milk will not correct a deficiency because the calcium in the milk inactivates the vitamin D, so the amount available to your body is not increased no matter how much milk you drink.