Whereas vitamin D deficiency has long been recognized as a medical condition, vitamin D “insufficiency” has recently become a concern. Increased attention to this new “syndrome” has led to a substantial increase in testing for vitamin D levels in the blood, and it is expected that several million tests will be performed in the U.S. this year. If you worry about your vitamin D levels or wonder how much vitamin D is right for you, here are some tips.

1. Vitamin D insufficiency is not uncommon.

According to a new federal government study released in March by the U.S. National Center for Health Statistics, about a fourth of U.S. residents are at risk for vitamin D inadequacy and 8 percent are at risk for vitamin D deficiency. An additional 1 percent of Americans have vitamin D levels so high as to be harmful.

2. Age, sex, skin color, sun exposure and fortified milk are factors.

Vitamin D insufficiency or deficiency is especially likely in older adults because they have decreased ability to make vitamin D and tend to have limited sun exposure. If you are a postmenopausal woman and have a family member who has had osteoporosis, you are at risk for weakened bones and may need to check your vitamin D levels. Dark skin, lack of sunlight and not using fortified milk may often be related to vitamin D insufficiency or deficiency.

3. A simple blood test can reveal your vitamin D levels.

Once you are concerned about a low level of vitamin D, you may ask your doctor about having a blood test. It is easy and just a small sample of blood may be needed to show your vitamin D levels. But remember that a blood test for vitamin D is quite new and sometimes your blood sampling needs to be referred to a larger hospital than the usual primary care clinic, and this may cost extra money.

4. Both vitamin D and calcium are essential for bone health.

For bone health, vitamin D and calcium go hand in hand. Vitamin D is the director, but the star of the show is calcium because vitamin D must be adequate in your body for calcium to be absorbed from the digestive tract. A low level of vitamin D prevents you from absorbing enough calcium for good bone health even though you have extra calcium intake. That is why dairies fortify their milk with vitamin D. It also explains why many doctors recommend calcium supplements with vitamin D for their patients with weak bones or osteoporosis.

5. The sun dilemma makes it worse.

Vitamin D is different from all the other nutrients in that it can be synthesized in your skin with the help of sunlight. This is why we call vitamin D “the sunshine vitamin.”

Therefore, vitamin D is not an essential nutrient; given enough time in the sun, people need no vitamin D from foods. Prolonged exposure to sunlight, however, prematurely wrinkles the skin and can cause skin cancer. Being in the sun is essential for both health and mood but there should be a good balance between limited and too much exposure.

6. The RDA for vitamin D has been increased from 400 to 600 IU.

The Institute of Medicine (IOM) released in November 2010 a new recommended dietary allowance (RDA) for vitamin D of 600 IU a day for most healthy adults. The RDA goes up to 800 IU a day for adults age 71 and older. People who are not outdoors much or who live in northern or predominantly cloudy or smoggy areas are advised to drink at least 2 cups of vitamin D-fortified milk a day. A cold glass of milk may refresh as it replenishes vitamin D and other bone-building nutrients. The IOM warns against routine use of high-dose supplements of vitamin D because of concerns about adverse health effects.

7. Consuming salmon may be good for both your heart and vitamin D.

Only a few foods ― notably oily fish ― contain vitamin D naturally. Salmon, mackerel and sardines are good sources of vitamin D. The American Heart Association recommends adults consume at least 2 servings of oily fish per week because the high content of omega-3 in these fish can help your heart. By consuming oily fish, you may have good health effects for your heart and vitamin D as well. 

By Young-Hoon Kwon, M.D.

The writer is on the staff at the Center for Health Promotion, Samsung Medical Center. ― Ed.