A new study looking at the relationship between
vitamin D serum levels and the risk of colon and breast cancer
across the globe has estimated the number of cases of cancer
that could be prevented each year if vitamin D3 levels met the
target proposed by researchers.
Cedric F. Garland, Dr.P.H., cancer prevention specialist at the
Moores Cancer Center at the University of California, San Diego
(UCSD) and colleagues estimate that 250,000 cases of colorectal
cancer and 350,000 cases of breast cancer could be prevented worldwide
by increasing intake of vitamin D3, particularly in countries
north of the equator. Vitamin D3 is available through diet, supplements
and exposure of the skin to sunlight.
"For the first time, we are saying that 600,000 cases
of breast and colorectal cancer could be prevented each year
worldwide, including nearly 150,000 in the United States alone,"
said study co-author Garland. The paper, which looks at the
dose-response relationship between vitamin D and cancer, will
be published in the August edition of the journal Nutrition
Reviews.
The study combined data from surveys of serum vitamin D levels
during winter from 15 countries. It is the first such study
to look at satellite measurements of sunshine and cloud cover
in countries where actual blood serum levels of vitamin D3 had
also been determined. The data were then applied to 177 countries
to estimate the average serum level of a vitamin D metabolite
of people living there.
The data revealed an inverse association of serum vitamin D
with risk of colorectal and breast cancer. The protective effect
began at levels ranging from 24 to 32 nanograms per milliliter
of 25-hydroxyvitamin D concentration in the serum. The 25-hydroxyvitamin
D level is the main indicator of vitamin D status. The late
winter average 25-hydroxyvitamin D in the US is about 15-18
ng/ml. The researchers maintain that increasing vitamin D levels
in populations, particularly those in northern climates, has
the potential to both prevent and possibly serve as an adjunct
to existing treatments for cancer.
The work builds on previous studies by Garland and colleagues
(Journal of Steroid Biochemistry and Molecular, February 2007)
which found that raising the serum 25(OH)D levels to 55 ng/mL
was optimal for cancer prevention. This is the first study to
recommend optimal vitamin D serum levels which, Garland said,
are high enough to provide the needed benefit but which have
been found by other scientists to be low enough to avoid health
risks.
"This could be best achieved with a combination of diet,
supplements and short intervals -- 10 or 15 minutes a day --
in the sun," said Garland. It could be less for very fair-skinned
individuals. He went on to say that "the appropriate dose
of vitamin D in order to reach this level, could be very little
in a lifeguard in Southern California... or quite a lot for
someone in Northern Europe who tends to remain indoors most
of the year."
The serum level recommended by the study would correspond to
intake of 2000 International Units per day of vitamin D3 for
a meaningful reduction in colorectal cancer. The researchers
recommend 2000 IU/day, plus, when weather allows, a few minutes
in the sun with at least 40% of the skin exposed, for a meaningful
reduction in breast cancer incidence, unless the individual
has a history of skin cancer or a photosensitivity disease.
Garland also recommends moderate sun exposure and use of clothing
and a hat when in the sun longer than 15 minutes.
This paper used worldwide data only recently available through
a new tool called GLOBOCAN, developed by the World Health Organization's
International Agency for Research on Cancer. GLOBOCAN is a database
of cancer incidence, mortality and prevalence for 177 countries.
Previous studies from this core group have shown an association
between higher levels of vitamin D3 or markers of vitamin D
status and lower risk of cancers of the breast, colon, ovary
and kidney.
The researchers underscore their call for prompt public health
action to increase intake of vitamin D3 as an inexpensive tool
for prevention of diseases that claim nearly one million lives
each year world wide.
"The message is, depending on where you live, you may
need to consider taking in considerably higher levels of vitamin
D3 than those currently recommended," said Garland. "I'd
recommend discussing vitamin D needs with a health care professional,
who may order and interpret a simple blood test for a vitamin
D metabolite [25(OH)D], and provide a dosage recommendation
that's appropriate for the individual's needs."
