Date: 24-Mar-09
Country: US
Author: Andrew Stern
CHICAGO - The "sunshine vitamin," vitamin D, is increasingly seen as vital to health, yet more Americans are not getting enough, US researchers said on Monday.
Analyzing data from government health surveys, researchers from the University of Colorado Denver School of Medicine found three out of four Americans had "insufficient" levels of vitamin D, up from about one out two 20 years ago.
A simple blood test can determine whether someone has what most researchers believe is an ideal level of vitamin D of between 30 and 40 nanograms per millilitre of blood.
Getting enough can be simple: spend 10 minutes in the sun with legs and arms exposed, or take vitamin supplements in pill form.
"But people's habits have changed ... they are less active and outdoors less, and also protecting their skin from the sun because of skin cancer risk," said Dr. Adit Ginde, who with colleagues did the study published in the Archives of Internal Medicine.
Slathering on sunscreen and wearing clothing and hats to protect skin from the sun's rays also halts production of vitamin D in the skin.
Traditionally, vitamin D has been seen as vital to bone health and to prevent rickets, but recent discoveries show many types of cells in the body contain vitamin D receptors, which indicates they use vitamin D in some way, Ginde said.
The vitamin regulates 1,000 genes, he said, and is believed to have a role in preventing cardiovascular disease and cancer, and regulating the immune system.
DANGEROUS DEFICIENCY
In a telephone interview, Ginde said the biggest concern unearthed by his comparison of data on 18,000 Americans from 1988 to 1994 and 13,000 from 2001 to 2004 was the proportion whose vitamin D levels were deemed dangerously deficient.
The percentage of Americans who had less than 10 nanograms per millilitre of blood tripled to 6 percent from 2 percent, putting them at risk of developing rickets and bone problems.
Food can boost vitamin D levels, but only a few foods contain significant amounts. Those include some types of fish -- salmon, sardines, tuna and mackerel -- and most dairy products that are enriched with the vitamin. But the amounts in dairy are primarily designed to keep people from falling into the deficient category, Ginde said.
"Given the guidelines currently existing, most Americans could use more vitamin D," Ginde said.
"In the last few years, vitamin D has gained more attention both in the media and the scientific literature. I think people are paying a lot more attention to it, people are taking more supplements, or having that small amounts of sun exposure, so I think we'll see a levelling of the downward trend," he said.
A second study in the journal supported the idea of providing higher doses of vitamin D for bone health.
In an analysis of nine previously published studies of adults aged 65 or older, researchers at the University of Zurich found non-spinal bone fractures decreased 20 percent when the patients took at least 400 international units of vitamin D per day.
Researcher Heike Bischoff-Ferrari and colleagues wrote in the report, "it is possible that greater benefits may be achieved with earlier initiation of vitamin D supplementation and longer duration of use."
(Editing by Maggie Fox and Cynthia Osterman)
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