Over the past six months, newspaper articles have cited studies linking inadequate intake of vitamin D or the lack of its production by the skin to a heightened risk of cancer.

An association between vitamin D and cancer has long been suspected because exposure to ultraviolet light is the major source of vitamin D formation in the body, and people in sunny, southern latitudes were found to have lower cancer rates than people in less sunny, northern regions. People living in sunnier climes, however, would be expected to have higher exposures to cancer-causing UV radiation.

Further support for this relationship had come from a few studies showing that people taking supplements of vitamin D lowered their risk of developing certain cancers.

But now a new study of nearly 17,000 Americans, published in October in the Journal of the National Cancer Institute, has found no relationship between blood levels of vitamin D and the overall risk of dying of cancer during the following 10 years.

This study did find one link between vitamin D levels and a particular cancer: The risk of death from colon cancer was significantly lower in those with higher blood levels of vitamin D. No association, however, was found between vitamin D levels and deaths from cancers of the lung, breast, and prostate, or from leukemia, lymphoma, or other forms of cancer.

The new study is far from perfect, though. For example, participants' vitamin D levels were only measured once, even though vitamin D formation varies widely at different times of the year. Establishing any definitive connection between vitamin D and a risk of cancer will require further large, prospective studies.

Adequate levels of vitamin D are essential to maintaining bone health, and supplements of vitamin D and calcium are often recommended to prevent osteoporosis, since low levels of vitamin D are quite common in this country.

On the other hand, excessive intake of vitamin D for possible prevention of cancer can cause serious side effects from elevated blood levels of calcium (hypercalcemia), including nausea and vomiting, increased thirst and urination, kidney stones, peptic ulcer, and high blood pressure.