Presentazione

da "www.healthnews.com"

Published:  4 August 2009
 
It’s called the sunshine vitamin because given a sufficient amount of sunlight the human body manufactures vitamin D, which has long been known to be essential to bone and muscle health by aiding calcium absorption in the intestines and the production of enzymes involved in collagen formation in the bones. But more recent research has found receptors for vitamin D in almost every organ and tissue system in the body, suggesting that deficiencies may affect many types of cell functions and increase the risk of not only osteoporosis but many other diseases. Ten to fifteen minutes of sunshine 3 times a week is enough to produce the body’s requirement of this cheery nutrient, but apparently that is easier said than done—even for the nation’s youngsters.

Two new studies designed to assess the possible effects of low vitamin D levels on cardiovascular risk factors in young Americans uncovered some very disturbing facts. For example, one analysis showed that overall 7 out of 10 American children are not getting the vitamin D they need. About 7.6 million (9 percent) children, adolescents and young adults aged 1 through 21 are vitamin D deficient, with blood levels under 15 nanograms per milliliter. An additional 50.8 million (61 percent) have slightly higher levels, at between 15 and 29 nanograms per milliliter, but still low enough to be insufficient. “It’s astounding,” said the study’s lead, Dr. Michal L. Melamed of the Albert Einstein College of Medicine in New York. “At first, we couldn’t believe the numbers. I think it’s very worrisome.”

Melamed’s study found that low vitamin D levels were especially common among those who were female, adolescent, with darker skin, obese, drank milk less than once a week, or spent more than four hours daily watching television, playing videogames or using computers. “This appears to be another result of our unhealthy lifestyles, including a sedentary society that doesn’t go out in the sun much,” she said. “The widespread use of sunscreens, which block UV-B rays, has only compounded the problem.”

The second study, led by Jared P. Reis, an epidemiologist in the division of cardiovascular sciences of the U.S. National Heart, Lung, and Blood Institute, found an association between low Vitamin D levels and increased risk for high blood pressure, high blood sugar, and a condition known as metabolic syndrome that increases the risk for heart disease and diabetes. The 25 percent of young people with the lowest vitamin D levels were more than twice as likely to have high blood pressure and elevated blood sugar levels, nearly four times as likely to have metabolic syndrome and 54 percent more likely to have low HDL (“good”) cholesterol levels, compared to those with higher vitamin D levels.

Reis stressed, however, that although there is a clear association between vitamin D deficiency and cardiovascular risk factors, parents should not panic. “I believe we need additional research,” he said. “Our study is observational, and we need additional studies to confirm it.” He said there is also no need for parents to turn to supplements to provide the recommended 400 IU daily intake of vitamin D as adequate amounts can be achieved through sunlight exposure or consuming foods fortified with the nutrient.

Melamed agrees. “Parents should focus on modifiable risk factors,” she said. “Children should not always be on the computer or watching television. They can drink more milk, rather than using supplements.”

These findings come as the National Academy of Sciences Institute of Medicine reviews the federal government’s official guidelines for recommended daily intake of vitamin D. A public hearing is scheduled at the National Academy of Sciences in Washington as part of the process.

Both studies are published in the August 3 online issue of Pediatrics