A recent study published in the American Thoracic Society's American
Journal of Respiratory and Critical Care Medicine reports
that vitamin supplements do not protect against lung cancer, and may in
fact increase the risk of developing it.
Dr. Christopher
G. Slatore of the University of Washington and colleagues performed the
analysis by selecting a prospective cohort of 77,126 people between 50
and 76 years of age who were all in the Washington State VITAL
(VITamins And Lifestyle) program. The researchers analyzed the rate of
lung cancer development over four years and how it correlates with
current and past vitamin usage, smoking, and other characteristics
pertaining to demography and medical history.
Slatore writes,
"Our study of supplemental multivitamins, vitamin C, vitamin E and
folate did not show any evidence for a decreased risk of lung cancer."
In addition, he notes that participants who increased intake of
supplemental vitamin E had slightly higher risks of lung cancer.
From
the 77,126 people, 521 developed lung cancer; this is in line
with
the expected rate for this low-risk group. However, those who did
develop lung cancer had a slight significant association between lung
cancer and supplemental vitamin E in addition to the typical
associations
with smoking history, family history, and age.
According to the model, a person taking 100 mg/day of vitamin E for ten
years increases the risk of lung cancer by seven percent. This is like
a 28 percent increase in risk for a 400 mg/day dose for ten years.
Slatore notes that this increase in risk was largely confined to
current smokers.
Since so many people currently or used to smoke and so many people take
vitamin supplements, the study findings can benefit public
health. "Future studies may focus on other components of
fruits and vegetables that may explain the decreased risk [of cancer]
that has been associated with fruits and vegetables," notes Dr.
Slatore. "Meanwhile, our results should prompt clinicians to
counsel patients that these supplements are unlikely to reduce the risk
of lung cancer and may be detrimental."
An editorial in the same journal issue by Dr. Tim Byers of the
University of Colorado School of Medicine suggests people want to
easily take a pill instead of eating a healthy diet, and this is why
they believe that vitamin supplements are healthy or relatively
harmless.
However, "fruits contain not only vitamins but
also many hundreds of other phytochemical compounds whose functions are
not well understood," writes Byers. One study found a 20 percent
increase in cancer risk among people who ate the least amount of fruit,
and this has led to the World Cancer Research Fund and the American
Cancer Society to recommend two fruit servings each day.
Two servings of fruit per day "would likely lead to a reduced risk for
lung cancer, as well as
reduced risk of several other cancers and cardiovascular disease,"
writes Dr. Byers. "However, any benefit to the population of smokers
from increasing fruit intake to reduce cancer risk by 20 percent would
be more than offset if even a small proportion of smokers decided to
continue tobacco use in favor of such a diet change."
Long-Term Use of Supplemental Multivitamins, Vitamin C,
Vitamin E, and Folate Does Not Reduce the Risk of Lung Cancer
Christopher G. Slatore, Alyson J. Littman, David H. Au, Jessie A.
Satia, and Emily White
American. Journal of Respiratory and Critical Care Medicine.
2008; 177: pp. 524-530.
doi:10.1164/rccm.200709-1398OC
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: Peter M Crosta