Caffeine, Breast Cancer Link Minimal
Study Shows No Overall Increased Risk for Coffee Drinkers
By
Salynn Boyles
WebMD Health News
Reviewed By
Louise Chang, MD
Oct. 13, 2008 -- There's good news for women who can't get through the day
without their coffee fix.
In new findings from the Women's Health Study, caffeine consumption was not associated with an overall
increase in breast cancer.
Over 10 years of follow-up, women who drank four or more cups of coffee a
day had the same overall risk of breast cancer as women who almost
never drank coffee.
There was some suggestion that heavy caffeine consumption was associated
with an increased risk for benign breast disease and that caffeine may speed
the progression of aggressive forms of breast cancer.
But study co-author Shumin M. Zhang, MD, of Brigham and Women's Hospital and
Harvard Medical School, says it is not clear if this observation was real or a
chance finding.
"I would interpret this subgroup analysis with caution," she tells
WebMD. "These findings really should reassure women. From this and other
studies, I would say that it is pretty clear that there is no overall increase
in risk."
Coffee, Caffeine, and Breast Cancer
Last May, one of those studies, which included nearly 86,000 female nurses
followed for 22 years, also showed no overall increase in breast cancer risk
associated with coffee or caffeine consumption.
The findings, by well-known nutrition researcher Walter Willett, MD, and
colleagues from the Harvard School of Public Health, did suggest a slight
increase in breast cancer risk among postmenopausal women.
But like Zhang, Willett says women should not be too worried by the subgroup
finding.
"I wouldn't pay too much attention to this," he tells WebMD.
"The consistent thing in all the research is that nobody has seen an
overall increase in breast cancer risk."
In the study by Zhang and colleagues, 1,188 of the 38,432 study participants
developed invasive breast cancer over 10 years of follow-up.
Based on the women's responses to surveys about the foods they ate, the
researchers concluded that consumption of caffeine and caffeinated beverages
and foods was not significantly associated with an overall increased risk of
breast cancer.
Among women with benign breast disease, a nonsignificant positive
association with breast cancer risk was seen in those who drank four or more
cups of coffee a day and in those with the highest caffeine consumption
overall.
There was also a suggestion in heavy caffeine consumers of an increased risk
for tumors that are negative for both estrogen receptor (ER) and progesterone receptor (PR)
and for tumors larger than 2 centimeters -- factors associated with a poorer
prognosis.
This finding suggests that caffeine may speed the progression of existing
tumors, but Zhang says more research is needed to determine if this finding is
real.
The study appears in the Oct. 13 issue of the Archives of Internal
Medicine.
Decades of Study on Caffeine and Health
Willett's study did not find a link between caffeine and ER/PR negative or
larger tumors.
And after decades of research examining caffeine, coffee, and health,
Willett says there is very little to suggest an impact, either positive or
negative, on any cancer.
"In fact, it is very hard to pin anything on coffee or caffeine at this
time," he says. "There is a hint of an increased risk of fractures, but there doesn't seem to be much
there."
He adds that coffee and caffeine have been found to be protective against type 2
diabetes in several studies and a research analysis.
"It is fair to say that, so far, the overall balance of risks and
benefits are on the side of benefits," he says.
SOURCES: Ishitani, K.l. Archives of Internal Medicine, Oct. 13, 2008; vol 168:
pp 2022-2031. Shumin M. Zhang, MD, ScD, associate professor of medicine, Harvard School of
Medicine and Division of Preventive Medicine, Brigham and Women's Hospital,
Boston. Walter Willett, MD, MPH, chair, department of nutrition; professor of
epidemiology and nutrition, Harvard School of Public Health, Boston. Willett, W. International Journal of Cancer, May 2008.
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