During the past few years, interest in vitamin D has grown rapidly. In fact, more than 1,500 scientific articles were published about vitamin D so far this year. Two key practical concepts have emerged from this research: 1) Many of today's common health problems might be related to inadequate vitamin D; or 2) possibly half of the population has inadequate vitamin D status.

Question: What types of health problems are linked to vitamin D?

Answer: In addition to vitamin D's important role in maintaining a strong skeleton, it has many other functions. Vitamin D also enhances the function of the immune system and reduces inflammatory activity.

According to the Vitamin D Council, “;Current research has implicated vitamin D deficiency as a major factor in the pathology of at least 17 varieties of cancer, as well as heart disease, stroke, hypertension, autoimmune diseases, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects, periodontal disease and more.”;

QUESTION: How can vitamin D be involved in so many health problems?

ANSWER:Vitamin D works like a hormone, regulating some of the basic functions of many types of cells throughout the body. If one or more of these functions is compromised, a variety of diseases could occur.

Q: Isn't vitamin D known as the sunshine vitamin?

A: It is true that sunlight can convert a form of cholesterol in the skin to vitamin D-3. However, sun exposure does not always maintain healthy vitamin D levels. A study of 93 young adults living on Oahu found that despite “;abundant sun exposure”; averaging around four hours of sunlight per day, half of the study participants had low vitamin D status. This was an unexpected finding that still remains to be explained. A later study conducted in Arizona found similar results.

Q: How is vitamin D status measured?

A: Evaluation of vitamin D status involves the measurement of blood levels of a form of vitamin D called 25-hydroxyvitamin D. The use of this test is growing increasingly common as physicians find more scientific support to justify the tests.

Q: How much vitamin D do we need?

A: Since excessive sun exposure can be damaging to skin, many people opt for food and dietary supplement sources of this vitamin. Recommendations for vitamin D are changing rapidly. Vitamin D researchers are suggesting that young adults need about 10 times as much daily intake as the current official recommendation, set back in 1997, states—about 2,000 IU (international units) instead of 200 IU. Ultimately, the goal is to obtain enough vitamin D to maintain normal blood levels.

Q: Does vitamin D protect against viral infections?

A: Stay tuned. It is known that normal vitamin D status benefits the immune system. However, studies are needed to determine how this affects susceptibility and response to viral infections.

Q: How much vitamin D is too much?

A: Vitamin D experts are suggesting that the current “;tolerable upper intake level”; of 2,000 IU per day be increased to 10,000 IU per day.

Joannie Dobbs, Ph.D., C.N.S., and Alan Titchenal, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dobbs also works with University Health Services.