The D Vitamins

Vitamin D is a nutrient found in some foods that is needed for health and to maintain strong bones. It does so by helping the body absorb calcium (one of bone’s main building blocks) from food and supplements. People who get too little vitamin D may develop soft, thin, and brittle bones, a condition known as rickets in children and osteomalacia in adults.

Vitamin D is important to the body in many other ways as well. Muscles need it to move, for example, nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses. Together with calcium, vitamin D also helps protect older adults from osteoporosis. Vitamin D is found in cells throughout the body

 

Effects of vitamin D on health

Vitamin D is being studied for its possible connections to several diseases and medical problems, including diabetes, hypertension, and autoimmune conditions such as multiple sclerosis. Two of them discussed below are bone disorders and some types of cancer.

Bone disorders; As they get older, millions of people (mostly women, but men too) develop, or are at risk of, osteoporosis, where bones become fragile and may fracture if one falls. It is one consequence of not getting enough calcium and vitamin D over the long term. Supplements of both vitamin D3 (at 700–800 IU/day) and calcium (500–1,200 mg/day) have been shown to reduce the risk of bone loss and fractures in elderly people aged 62–85 years. Men and women should talk with their health care providers about their needs for vitamin D (and calcium) as part of an overall plan to prevent or treat osteoporosis.

Cancer; Some studies suggest that vitamin D may protect against colon cancer and perhaps even cancers of the prostate and breast. But higher levels of vitamin D in the blood have also been linked to higher rates of pancreatic cancer. At this time, it’s too early to say whether low vitamin D status increases cancer risk and whether higher levels protect or even increase risk in some people.

 

Foods that provide vitamin D

Very few foods naturally have vitamin D. Fortified foods provide most of the vitamin D in American diets.

  • Fatty fish such as salmon, tuna, and mackerel are among the best sources.
  • Beef liver, cheese, and egg yolks provide small amounts.
  • Mushrooms provide some vitamin D. In some mushrooms that are newly available in stores, the vitamin D content is being boosted by exposing these mushrooms to ultraviolet light.
  • Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart. But foods made from milk, like cheese and ice cream, are usually not fortified.
  • Vitamin D is added to many breakfast cereals and to some brands of orange juice, yogurt, margarine, and soy beverages; check the labels.

 

Vitamin D may improve bone health in those taking anti-HIV drug

NIH study suggests benefits for young people on long-term tenofovir treatment
Vitamin D may help prevent hormonal changes that can lead to bone loss among those being treated for HIV with the drug tenofovir, according to the results of a National Institutes of Health network study of adolescents with HIV.

Tenofovir is widely used to treat HIV infection. However, the drug causes symptoms that resemble those of vitamin D deficiency ods.od.nih.gov/factsheets/VitaminD-QuickFacts, causing bones to lose calcium and reducing bone density. The study found that large monthly doses of vitamin D reduced blood levels of a hormone that stimulates calcium release from bones.

“What we’ve found suggests vitamin D could be used to counteract one of the major concerns about using tenofovir to treat HIV,” said Rohan Hazra, M.D., of the Pediatric, Adolescent and Maternal AIDS Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the NIH institute that funds the networks. “People in their teens and twenties may be on anti-HIV treatment for decades to come, so finding a safe and inexpensive way to protect their long-term bone health would be a major advance.”

The findings were published online in Clinical Infectious Diseases.

Vitamin D helps the body absorb calcium to build bones. When the body is deficient in vitamin D, levels of a hormone called parathyroid hormone rise. This rise triggers activity that draws calcium from bones. As a result, the bones become more fragile and can break more easily. Parathyroid hormone also tends to be elevated in people taking tenofovir, whether or not they have sufficient vitamin D.

Because parathyroid hormone levels are elevated in people taking tenofovir in much the same way as they are in people with vitamin D deficiency, the researchers theorized that vitamin D might counteract the bone-depleting effects of tenofovir.

The study was conducted by first author Peter L. Havens, M.D., of the Medical College of Wisconsin and Children’s Hospital of Wisconsin, Milwaukee; Dr. Hazra; Kathleen Mulligan, Ph.D., of the University of California at San Francisco; and other researchers affiliated with the Adolescent Medicine Trials Network for HIV/AIDS Interventions (ATN) and the International Maternal–Pediatric–Adolescent AIDS Clinical Trials (IMPAACT) Group.

In addition to funding from NICHD, funding was also provided by the National Center for Research Resources, the National Institute on Drug Abuse, and the National Institute of Mental Health.

About 200 18- to 25-year-olds on antiretroviral therapy took part in the study. Study participants included young adults taking tenofovir and those receiving other forms of anti-HIV treatment. Each month, the adolescents and young adults in the study took a 50,000-unit dose of vitamin D or placebo. At the end of the three months, parathyroid hormone levels had fallen about 14 percent among participants taking tenofovir and vitamin D but remained unchanged in participants taking other kinds of anti-HIV medication. However, youth taking tenofovir still had higher parathyroid hormone levels than those on other anti-HIV drugs. The researchers don’t know if longer treatment with vitamin D would further reduce parathyroid hormone levels.

The recommended daily dose of vitamin D is 600 units. The authors noted that they observed no adverse effects from the vitamin D treatment during the 3 months of this study.

The researchers are now making plans for a two-year follow-up study to examine the longer-term safety of vitamin D in a similar group of HIV-infected youth taking antiretroviral regimens containing tenofovir, and to determine if the changes in parathyroid hormone result in improvements in bone density.

About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute’s website at http://www.nichd.nih.gov/.

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