Vitamin Information Center

DEAR DR. DONOHUE: I am a 76-year-old female. Until December 2005, I thought I was in fairly decent health. That’s when I suffered a fractured hip. I didn’t fall, just sort of slipped down. I have recovered and feel great, and I exercise. Last April, my doctor prescribed 50,000 IU vitamin D once a week. I have been taking it ever since. I get lots of sun. I also take 600 mg of calcium with 200 IU vitamin D twice a day. And I take one multivitamin a day, a Centrum Silver. My doctor wants me to consider taking Fosamax. What’s going on? I worry about getting too much vitamin D. How does a person know how much is too much?

— T.W.

Most adults get too little vitamin D. The official recommendation for daily vitamin D intake is 200 IU for those from 19 to 50, 400 IU for those between 51 and 70, and 600 IU for those 71 and older. Many experts believe these recommendations are insufficient and that the daily dose should be 800 IU to 1,000 IU. Vitamin D enhances calcium absorption and plays a critical role, therefore, in keeping bones strong and in preventing fractures. There are hints that vitamin D prevents osteoarthritis, lessens the risk of prostate cancer and helps prevent diabetes and heart disease. Time will tell if all this is true. The stuff about bones is true.

We get vitamin D when sunlight strikes the skin. It turns a substance in the skin known as a “provitamin” into vitamin D. Ten minutes of sunlight on the face and arms, three times a week to daily, is all the sunlight needed for this conversion. Older people’s skin is not so efficient in making the vitamin, and those living in northern latitudes can’t depend on sunlight conversion in the winter months.

From your weekly 50,000 IU tablet, you get about 7,000 IU of the vitamin daily. Centrum Silver has 500 IU. You get another 400 IU with your daily calcium tablets. So your daily intake is around 8,000 IU. Too much vitamin D can be a problem. It can damage the kidneys and can actually draw calcium from the bones. The upper daily limit is set at 10,000 IU. You haven’t crossed the border, but you’re in its neighborhood. The 50,000 IU tablet can correct a vitamin D deficiency in six to eight weeks. I’d say you’ve made that correction. Ask your doctor about stopping this high-dose vitamin therapy. If there is a question about the adequacy of your body store of vitamin D, a blood test can determine if it is too low, too high or just right.

DEAR DR. DONOHUE: Our 21-year-old daughter has been diagnosed with peripheral neuropathy. Her finger turned a shade of blue. She went to the emergency room and got the diagnosis there. What kind of doctor should we consult to determine if this is her condition?

— V.C.

Your family doesn’t have a history of having peripheral neuropathy, right? So let’s remove all the genetic causes of it from consideration.

Twenty-one is young to come down with it. It’s more of an older person’s illness. People with diabetes and a few other diseases also are targets for it, but your daughter is in otherwise good health.

A blue finger isn’t a usual sign. Your daughter should see a neurologist or a vascular specialist to confirm this diagnosis, which appears a bit strange to me.

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The days are finally getting longer, but the cold and wind have kept us indoors through much of this winter. Even if we were outside on a regular basis, our skin would produce very little, if any, vitamin D. While the sun is closest to the earth in winter, the sun’s rays are entering at such an oblique angle (zenith angle) the solar ultraviolet B (UVB) rays are blocked by the ozone layer — and it is this solar UVB radiation that stimulates vitamin D production. But even in the summer, in the early morning and late afternoon, the zenith angle of the sun’s rays is so oblique that very little vitamin D is produced in the skin.

Why is this important? Vitamin D is recognized as the sunshine vitamin, and if we get little UVB radiation, we produce very little vitamin D. More than 90 percent of the vitamin D we need comes from casual exposure to sunlight.

But production decreases sharply with increased skin pigmentation (racial or seasonal), advancing age and use of sunscreens. Other important factors include the season and even the time of day. As a result, dark skinned individuals and the elderly may suffer from vitamin D deficiency, especially during the winter months.Vitamin D is assumed to be plentiful in a healthy diet but, in truth, very few foods naturally contain it and only a few are fortified with it. Moreover, recommended intakes of vitamin D are not sufficient to prevent deficiency. This, together with the widespread use of sunscreens and an overall lack of sunshine exposure, is the reason vitamin D deficiency is now epidemic in the United States.

Adults with vitamin D deficiency absorb calcium poorly and are at increased risk for osteoporosis and related fractures. If this deficiency is not corrected, extreme degrees of deficiency may ensue, leading to the painful bone disease of osteomalacia.

Other consequences of vitamin D deficiency include impaired neuromuscular function with poor balance, decreased muscular strength and increased falls. Individuals may complain of deep aching bone pain, weakness and muscular discomfort. Such patients are often misdiagnosed with fibromyalgia, chronic fatigue, myositis or other nonspecific conditions. It has been estimated that 40 to 60 percent of patients with fibromyalgia may have some component of vitamin D deficiency and osteomalacia. Vitamin D deficiencies have been demonstrated to increase the risks of many autoimmune diseases including Type 1 diabetes, rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease and psoriasis. Another action of vitamin D is thought to be important in keeping cell growth in check, and preserving normal cellular proliferation and differentiation, thus preventing cells from developing into unregulated cancers. Deficiency of vitamin D is now felt to contribute to several major cancers, notably

prostate, colon and breast.

So what can be done to prevent vitamin D deficiency? First, it’s important to recognize that it exists, that it is epidemic and that it may affect you since no age group is immune. Even teenagers and children are at risk. Second, get sensible sun exposure — 5 to 10 minutes at a time, two to three times per week between the hours of 10 a.m. and 3 p.m. in the spring, summer, and fall. (It is equally important to avoid chronic, excessive exposure to sunlight which increases the risk of nonmelanoma skin cancers.)

Increased dietary and supplemental vitamin D intakes of 800 to 1000 international units (IU) per day are reasonable and safe.

Maintaining a normal vitamin D status should be a high priority for all of us, with the help of our doctor.

– Dr. James Maddy practiced internal medicine and endocrinology in Casper for more than 30 years before retiring in 2004.

Much of the research for this article was take from the works and publications of Dr. Michael Holick, Boston University Medical Center, and Dr. Robert Heaney, Creighton University, in Omaha, Neb.