Vitamin Information Center

Unalaska has many great things to offer, but intense sunlight is not one of them. Although the lack of powerful sun may be good for reducing our skin cancer risk, it is not good for our vitamin D levels. The body uses sunlight to make vitamin D from molecules in the skin. Many who live at northern latitudes, especially in the winter, have inadequate vitamin D levels. A study in the British Medical Journal estimates at least 1 billion people worldwide are vitamin D deficient.

Most tissues in the body have receptors for this important vitamin. All of its many functions are still being discovered. The primary role of vitamin D is maintaining normal blood levels of calcium and phosphorous. Long term vitamin D deficiency leads to rickets in children and a softening of the bones in adults.

Currently there is much research being done to discover the additional effects of vitamin D in our bodies. A recent study published in the journal Dibetologia suggests that vitamin D may play a role in preventing type 1 diabetes in children. Vitamin D deficiency has been associated with increased risk of cardiovascular disease, according to a 2008 article in the journal Circulation.

A 2007 article in the New England Journal of Medicine states that people who live at higher latitudes who have vitamin D deficiency, or lack exposure to the sun, have an increased risk of many cancers. The same article suggests vitamin D may also provide protection from hypertension, psoriasis, several autoimmune diseases (including multiple sclerosis and rheumatoid arthritis) and reduce the incidence of fractured bones.

Make sure that you are getting enough vitamin D. It is difficult to get enough from the sun in the summer in Unalaska and impossible in the winter. Check out this Web site from the Norwegian Institute for Air Research to calculate how much vitamin D you are getting from the sun based on your location, weather, skin color, and clothing: http://nadir.nilu.no/~olaeng/fastrt/VitD_quartMED.html.

Obtaining adequate levels of vitamin D from your diet is not easy either. Good dietary sources include fortified milk, eggs, and fatty fish. Some studies, such as one published in the European Journal of Clinical Nutrition last year, have shown that the vitamin D fortification of milk products is not adequate to prevent vitamin D deficiency.

Infants who are breast fed are at particular risk vitamin D deficiency according to a 2004 study published in the American Journal of Clinical Nutrition. Human milk contains little vitamin D, and women who are vitamin D deficient provide even less to their breast-fed infants.

There are differing opinions on the recommended daily intake, especially in light of new studies coming out every day. The USDA recommended daily intake is 400 IUs for a healthy adult. Some physicians recommend much more than that, particularly for those deficient in the vitamin. Because vitamin D can be stored in our bodies, there are high dosages available that can be taken only once a week or once a month.

A 2003 study published in the Journal of Pediatrics looked at the vitamin D levels of women and infants in Alaska. Based on this study, the American Academy of Pediatrics recommends a universal supplement for all infants not receiving vitamin D fortified milk. Talk to your health care provider about getting the right amount of vitamin D for your health.

Tiffany Kelly is medical student from the University of Washington who visited Unalaska for the month of July, 2008. She now lives in Anchorage.

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.

Readers may write to Dr. Donohue or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.

Experts are increasingly pushing for higher daily recommended intakes of vitamin D, saying that while current amounts may prevent signs of deficiency, they are insufficient to provide a protective benefit against cancer.

Vitamin D is an essential nutrient produced by the body when ultraviolet radiation from sunlight strikes the skin. In northern latitudes, however, when sunlight is dim for significant parts of the year, many people cannot get enough sun to synthesize sufficient levels of the vitamin. This problem is particularly pronounced among those with darker skin. Few foods are rich in vitamin D. Fish oil and fortified food sources, such as milk or non-dairy milk substitutes, provide the most common dietary sources.

The United States and Canadian governments recommend a daily vitamin D intake of 200 IU. But vitamin D and cancer experts warn that this value is far too low.

Recently, the Canadian Cancer Society advised that light-skinned people take a 1,000 IU vitamin D supplement daily during fall and winter months, and that dark-skinned people or those who regularly keep all their skin covered while outdoors take a supplement year-round.

“We’re recommending 1,000 IU daily because the current evidence suggests this amount will help reduce cancer risk with the least potential for harm,” said Heather Logan, director of the society’s Cancer Control Policy.

“I have to commend the Canadian Cancer Society,” vitamin D researcher Joan Lappe said. “They’re right out in the lead there on changing the recommendations.”

Lappe was lead researcher in a recent study that found that women taking 1,100 IU of vitamin D per day showed a 60 percent reduced risk of developing cancer than women taking a placebo. Excluding women who developed cancer during the first year of the four-year study, the risk reduction from vitamin D was 77 percent.

In a paper published in the “American Journal of Clinical Nutrition,” a group of vitamin D experts recently advised that an upper daily limit of 10,000 IU be set for vitamin D exposure, making a break with the current, more cautious, government recommendations.

A vitamin is a small organic molecule essential for normal metabolism and growth. Since it cannot be synthesized by the body in adequate amounts, it must be obtained in the diet. According to this definition, vitamin D isn’t even a vitamin, since very large amounts can be synthesized in the skin. However, many if not most people don’t make enough vitamin D and need to consume it in food or supplements.

Vitamin D has been in the news a lot partly because of this very problem. It turns out that the skin can synthesize vitamin D only if it is exposed to adequate amounts of sunlight. So, people who don’t get a lot of sun, such as patients in hospitals, or elderly people living in institutions, are often deficient in vitamin D. Even healthy active adults, who live in northern latitudes, such as in New England, are frequently deficient in vitamin D, as are people who live in sunny climates but habitually cover their skin. The UV rays that produce vitamin D in the skin are the very same UV rays that produce sunburn and that are blocked by sunscreen, shade, clothing and dark skin pigmentation, so even people who are active outdoors can be deficient in vitamin D.

Why do we care? Vitamin D is essential for regulating blood calcium levels and for promoting calcium absorption to maintain strong bones. It also regulates certain immune functions and can decrease the proliferation of normal and cancerous cells. This may explain why low vitamin D levels are associated with increased risks of certain kinds of cancer and other diseases, and why vitamin D supplementation has been shown to decrease the risk of some cancers in post-menopausal women.

Fortunately, it is easy to supplement vitamin D levels. The recommended daily intake of vitamin D3 is 400 IU daily, although many experts recommend intake of 800 IU daily for children and adults. There are several good dietary sources: a 3.5 ounce serving of fresh wild salmon has between 600 and 1000 IU of vitamin D3 (farm-raised salmon may only contain 100 to 250 IU in the same size serving); canned tuna contains about 230 IU in a 3.6 ounce serving (which is a little more than half a can). Fortified milk, yogurt, cheese, orange juice and breakfast cereals often contain 100 IU of vitamin D3 per serving. Over-the-counter supplements containing vitamin D3 are also widely available.

Finally, there is the option of careful, sensible sun exposure. It is difficult to calculate “adequate” sun exposure because the amount of sun needed for a person to synthesize enough vitamin D varies with season, latitude, time of day and skin pigmentation. These factors affect the amount of UV that reaches and is absorbed by the skin. Also, older skin has less capacity to synthesize vitamin D. For most people, 5 to 10 minutes of sun exposure on the arms and legs twice a week may be enough to maintain vitamin D levels. With sun exposure, moderation is key; too much UV exposure and sunburns increase the risk of skin cancer. So, it is still important to avoid excessive sun exposure and to use sunscreen daily to minimize this risk.

Yes - a blood test called 25-hydroxyvitamin D, which, though expensive ($20 to $100 a pop), is covered by insurance. Your level should be at least 30 nanograms per milliliter of blood and not more than 100. If your level is way below that, say around 18, you need to take 1,200 international units or more a day of vitamin D supplements, either the type called D2 or D3, said Dr. Michael F. Holick, an endocrinologist and leading vitamin D researcher at the Boston University School of Medicine. Continue Reading…