Vitamin D

Are We Getting Enough Sun?

joko.catur@gmail.com (masjoko) — Sat, 29 Nov 2008 18:36:00 +0000

As the onset of winter begins to shorten our days and drive us indoors, our exposure to the sun is diminished. This can be a boon to those who can't stand the heat, or those who have fair skin. But could we be missing out on a very important aspect of being out in the sunshine? While most people know the risks of too much exposure to the sun's harmful rays, such as a higher risk of skin cancer, few of us stop to consider the risks of too little sun.

Simply put, exposure to the sun helps our bodies make vitamin D. Ultraviolet rays from sunlight trigger vitamin D synthesis in the skin, creating vitamin D for our bodies to use. A deficiency in this important vitamin can cause serious health problems, and vitamin D deficiencies are becoming more common than most of us realize.

Jacquelyn Dinusson, MD, Assistant Clinical Professor of Family and Community Medicine at the Medical College of Wisconsin, says that vitamin D deficiency occurs worldwide from dietary insufficiency, malabsorption of the vitamin by the intestines, and lack of exposure to the sun. It causes the bone disorder known as rickets, or osteomalacia, which is a weakening or softening of the bones, and it can lead to other health problems as well.

Dr. Dinusson explains, "Vitamin D assists with the absorption of calcium, with bone calcification, and with the reabsorption of calcium in the kidneys. Symptoms of vitamin D deficiency can include persistent nonspecific bone pain and muscle weakness. It may also cause symptoms associated with low calcium, including numbness around the mouth or in the extremities, abnormal heart rhythms, or spasms of the hands or feet." In addition, she says, vitamin D deficiency can lead to osteoporosis, or bone fractures from minimal trauma.

Who's at Risk?
Dr. Dinusson reports that the people most at risk of vitamin D deficiency are those with inadequate dietary intake of vitamin D and those with minimal sun exposure. This includes people who are malnourished, homebound, darker-skinned, or those living in a northern latitude. Additionally, exclusively breastfed infants without adequate vitamin D supplementation are at risk. "Infants drinking milk substitutes (unfortified soy, rice, almond, and oatmeal drinks) prior to one year of age may have vitamin D deficiency," Dr Dinusson says. Lastly, those who experience difficulty absorbing vitamin D are at risk. This can include people with liver or kidney disease and people taking certain drugs, including some seizure medications.

How Much Is Enough?
Physicians have a variety of methods for diagnosing a vitamin D deficiency if patients show symptoms. Otherwise, Dr. Dinusson gives us some general guidelines to follow: "The recommended daily intake of vitamin D for infants and children is 200 IU of vitamin D per day. Healthy adults require 400 IU daily, and those with certain medical problems or who are over seventy years old require 600 to 800 IU per day." There are a few foods that contain vitamin D, including egg yolks; fatty fish like sardines, mackerel, salmon, and herring; fish liver oils; shrimp; chicken liver; and oysters. Additionally, some foods are fortified with vitamin D, including cow's milk, breakfast cereals, and infant formulas, says Dr. Dinusson.

Eating foods that contain vitamin D is good, but exposure to the sun is much more efficient. According to the US Centers for Disease Control and Prevention (CDC), sun exposure is perhaps the most important source of vitamin D, because normal exposure to sunlight provides most humans with their total vitamin D requirement. However, season, geographic latitude, time of day, cloud cover, smog, and sunscreen use all affect UV ray exposure and vitamin D synthesis.

For example, sunlight exposure from November through February in Boston is insufficient to produce significant vitamin D synthesis in the skin. Complete cloud cover halves the energy of UV rays, and shade reduces it by 60%. Industrial pollution, which increases shade, also decreases sun exposure. Sunscreens with a sun protection factor (SPF) of 8 or greater will block UV rays that produce vitamin D, but it is still important to routinely use sunscreen to help prevent skin cancer and other negative consequences of excessive sun exposure.

An initial exposure to sunlight (10 -15 minutes) allows adequate time for Vitamin D synthesis and should be followed by application of a sunscreen with an SPF of at least 15 to protect the skin. Ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen is usually sufficient to provide adequate vitamin D.

Supplements
Supplements can play an important role for those who aren't getting enough vitamin D. Dr. Dinusson says the American Academy of Pediatrics recommends a minimum intake of 200 IU per day of vitamin D to exclusively breastfed children, starting within the first two months of life, unless the infant is also drinking more than 500 ml daily of vitamin D-fortified formula. At least 200 IU of vitamin D daily is also recommended for children and adolescents who do not have regular sunlight exposure or ingest greater than 500 ml daily of vitamin D-fortified milk.

"For elderly people," Dr. Dinusson says, "800 IU of vitamin D per day, along with calcium supplementation, may reduce hip fractures in residents of nursing homes or the frail elderly. I also recommend at least 400 IU of vitamin D with calcium supplementation to those diagnosed with osteoporosis. Anyone with risk factors for vitamin D deficiency, including lack of sun exposure, malabsorption of vitamin D, or dietary insufficiency should consider vitamin D supplementation."

Overall, Dr. Dinusson advises getting some exposure to sunshine every week, and eating foods that contain vitamin D. If you think you might be at risk for vitamin D deficiency, or exhibit any of the symptoms noted above, be sure to call your health care provider for testing.

Vitamin D Might Reduce Risk of Cardiovascular DiseaseVitamin D Might Reduce Risk of Cardiovascular Disease

joko.catur@gmail.com (masjoko) — Sat, 29 Nov 2008 18:32:00 +0000

Vitamin D Might Reduce Risk of Cardiovascular DiseaseVitamin D Might Reduce Risk of Cardiovascular Disease

Doctors are learning more about an important nutrient our bodies need in order to function optimally: vitamin D, which helps the body absorb calcium.

Research has indicated that vitamin D could provide protection from conditions such as osteoporosis, hypertension, cancer, infections, and some autoimmune disorders. And many of us - especially those who live in areas without much sunshine - don't get enough of it.

The authors of a study published in January 2008 in Circulation: Journal of the American Heart Association (Circulation. 2008;117:503-511) suggested that a deficiency of vitamin D may have an adverse effect on the cardiovascular system. That study caught the attention of Denise Teves, MD, Medical College of Wisconsin Assistant Professor of Medicine, whose practice focuses on Endocrinology, Metabolism and Clinical Nutrition.

"Until recently, we weren't fully aware of the relationship between vitamin D and heart disease," Dr. Teves said. "I'm happy we have this information, although we'll need a larger, more rigorous study to make final conclusions. Some cardiologists are still cautious about interpreting the results, but it certainly has raised eyebrows in the health community."

The study, part of the large, multi-year Framingham Heart Study, followed 1,739 healthy Caucasian men and women for more than five years. At the end of the study, the researchers found that those who were deficient in vitamin D - especially those who also had high blood pressure - had a higher incidence of heart disease.

The Framingham researchers noted that, although evidence suggests that low levels of vitamin D might adversely affect the cardiovascular system, it hasn't yet been proven that a deficiency actually increases the risk of cardiovascular disease.

Vitamin D and Heart Function
How does vitamin D affect heart function? There are several possible ways, Dr. Teves says. Perhaps due to anti-inflammatory properties, vitamin D might decrease the thickening of heart tissue that can lead to heart failure. Vitamin D can also balance the hormonal pathway that regulates blood pressure, and may reduce calcification in the cardiovascular system."

It is fairly well-established, Dr. Teves said, that a lack of vitamin D contributes to osteoporosis - a condition she sees frequently in her patients, many of whom are deficient or insufficient in vitamin D. After reading the Circulation study, she plans to develop a proposal to study vitamin D levels among patients with kidney failure.

How much vitamin D should we get daily? Much more than the current recommended daily requirement of 400 units, the amount commonly found in multivitamins, Dr. Teves says: "I would think people should consume at least twice that much - 800 units per day - and possibly as much as 2,000 units a day."

But it's important that patients discuss any supplementation with their physicians, Dr. Teves notes. Because it is a fat-soluble (rather than water-soluble) vitamin, vitamin D can build up in the body and potentially become toxic, resulting in symptoms including nausea, vomiting, poor appetite, constipation, weakness, and weight loss.

According to the Office of Dietary Supplements (ODS), high levels of vitamin D can also raise blood levels of calcium, causing heart rhythm abnormalities and mental status changes such as confusion.

Sources of Vitamin D
Sunlight is perhaps the most important source of vitamin D. Unfortunately, for those of us who live far from the equator, it's highly likely we're not getting enough vitamin D because we have limited sun exposure year-round. The Circulation study estimated that one-third to one-half of otherwise healthy older adults in the United States have low levels of vitamin D.

Only a few commonly consumed foods are good sources of vitamin D, according to the Office of Dietary Supplements. Most milk in the United States is fortified with vitamin D, and it's added to some cereals and orange juice. The richest food sources are cod liver oil, cooked fish such as salmon and mackerel, and tuna and sardines that are canned in oil.

"It can be difficult to get enough vitamin D from diet alone," Dr. Teves says, "so it's usually necessary to add vitamin D supplements, especially in winter." The Office of Dietary Supplements indicates that adults 50 and older require higher levels of vitamin D than do younger people.

"Vitamin D exerts a range of effects on bones and muscles," Dr. Teves said. "Researchers are studying the role of vitamin D in improving the response to infections and recurrence of cancer, and now, the possibility that it helps maintain a healthy heart."