Most Americans and others are not taking
enough vitamin D, a fact that may put them at significant risk
for developing cancer, according to a landmark study conducted
by Creighton University School of Medicine.
The four-year, randomized study followed
1,179 healthy, postmenopausal women from rural eastern
Nebraska.* Participants taking calcium, as well as a quantity
of vitamin D3 nearly three times the U.S. government’s
Recommended Daily Amount (RDA) for middle-age adults, showed a
dramatic 60 percent or greater reduction in cancer risk than
women who did not get the vitamin.
The results of the study, conducted between
2000 and 2005, were reported in the June 8 online edition of
the American Journal of Clinical Nutrition.
“The findings are very exciting. They
confirm what a number of vitamin D proponents have suspected
for some time but that, until now, have not been substantiated
through clinical trial,” said principal investigator Joan
Lappe, Ph.D., R.N., Creighton professor of medicine and holder
of the Criss/Beirne Endowed Chair in the School of Nursing.
“Vitamin D is a critical tool in fighting cancer as well as
many other diseases.”
Other Creighton researchers involved in the
study included Robert Recker, M.D.; Robert Heaney, M.D.; Dianne
Travers-Gustafson, M.S.; K. Michael Davies, Ph.D,; and Gleb
Haynatzki, Ph.D.
Research participants were all 55 years and
older and free of known cancers for at least 10 years prior to
entering the Creighton study. Subjects were randomly assigned
to take daily dosages of 1,400-1,500 mg supplemental calcium,
1,400-1,500 mg supplemental calcium plus 1,100 IU of vitamin
D3, or placebos. National Institutes of Health funded the
study.
Over the course of four years, women in the
calcium/vitamin D3 group experienced a 60 percent decrease in
their cancer risk than the group taking placebos.
On the premise that some women entered the
study with undiagnosed cancers, researchers then eliminated the
first-year results and looked at the last three years of the
study. When they did that, the results became even more
dramatic with the calcium/vitamin D3 group showing a startling
77 percent cancer-risk reduction
In the three-year analysis, there was no
statistically significant difference in cancer incidence
between participants taking placebos and those taking just
calcium supplements.
Through the course of the study, 50
participants developed nonskin cancers, including breast,
colon, lung and other cancers.
Lappe said further studies are needed to
determine whether the Creighton research results apply to other
populations, including men, women of all ages, and different
ethnic groups. While the study was open to all ethnic groups,
all participants were Caucasian, she noted.
There is a growing body of evidence that a
higher intake of vitamin D may be helpful in the prevention and
treatment of cancer, high blood pressure, fibromyalgia,
diabetes mellitus, multiple sclerosis, and rheumatoid arthritis
and other diseases.
Humans make their own vitamin D3 when they
are exposed to sunlight. In fact, only 10-15 minutes a day in a
bright summer sun creates large amounts of the vitamin, Lappe
said. However, people need to exercise caution since the sun’s
ultraviolet B rays also can cause skin cancer; sunscreen blocks
most vitamin D production.
In addition, the latitude at which you live
and your ancestry also influence your body’s ability to convert
sunlight into vitamin D. People with dark skin have more
difficulty making the vitamin. Persons living at latitudes
north of the 37th parallel – Omaha is near the 41st parallel –
cannot get their vitamin D naturally during the winter months
because of the sun’s angle.
Experts generally agree that the RDA** for
vitamin D needs to be increased substantially, however there is
debate about the amount. Supplements are available in two forms
– vitamin D2 and vitamin D3. Creighton researchers recommend
vitamin D3 , because it is more active and thus more effective
in humans.
** RDA recommendations for vitamin D are
200 IU/d, birth-age 50; 400 IU/d, 50-70 years; and 600 IU/d, 70
years and older.
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