Testing for vitamin
levels, once uncommon, has skyrocketed as medical
studies raise awareness about vitamin D deficiencies,
according to three of the USA's largest medical diagnostic
labs. Physicians agree that they're increasingly using
the blood test to find out whether their patients are
low on the vital vitamin.
Richard Reitz, a medical director
with Quest Diagnostics of Madison, N.J., says tests
ordered for vitamin D grew by about 80% from May 2007
to May 2008.
Burlington, N.C.-based Lab Corp.
of America witnessed a 90% leap in D test requests from
2007 to 2008, says Eric Lindblom, the company's senior
vice president of investor and media relations. Neither
company would release the actual numbers for competitive
The Mayo Clinic in Rochester, Minn.,
another of the country's largest diagnostic labs, processed
424,582 tests in 2007, up 74% from 2006. Ravinder Singh,
co-director for the endocrine lab at Mayo, expects that
the clinic will tally more than 500,000 tests by the
end of 2008.
The jump in vitamin D testing comes
after a slew of emerging research — much of which
has been published in the past few years — linking
vitamin D deficiency with some infectious diseases,
cancers, cardiovascular disease and autoimmune disorders,
says Patsy Brannon, professor of nutritional sciences
at Cornell University.
Other research indicates that many
Americans are deficient in vitamin D, and that is also
fueling the testing trend, says Catherine Gordon, director
of the bone health program at Children's Hospital Boston.
Though specialists who treat bone-related
conditions and the elderly regularly run D tests, now
even primary-care physicians and pediatricians are ordering
the blood analysis.
"Even a year ago, vitamin D testing
wasn't really being talked about among physicians in
a major way. But now I am testing 100% more than I did
in the past," says Janet Pregler, director of the Iris
Cantor-UCLA Women's Health Center and a professor of
medicine at UCLA.
A normal vitamin D test result
is 30 ng/mL (nanograms/milliliter) or above. If a reading
dips below that, a patient is considered insufficient;
under 20 ng/mL, and he or she is tagged deficient. Supplements
and D-rich foods, such as fortified milk, may be recommended
for patients with low D levels, Gordon says. The UV
rays in sunshine also activate one form of vitamin D
in the body, but increased sun exposure can lead to
Boston Medical School's Michael
Holick, a professor of medicine, physiology and biophysics,
says everyone should be taking 1,000 IUs (international
units) of vitamin D a day, even though the Institute
of Medicine recommends only 200 IUs a day for children
and 400 IUs daily for adults.
But UCLA's Pregler says the million-dollar
question remains: "Will supplementing D-deficient patients