A recent headline announcing the results of another study examining the role of alcohol and risk of breast cancer proclaimed that even a
glass of wine a day “can significantly increase a woman’s cancer risk.” The
connection between drinking and breast cancer has been a troublesome one, the
thorn among the rosés, if you’ll pardon the metaphor. It’s not that I mean to
make light of all this well-intentioned alarm bell ringing, but the way I see it
research on wine and breast cancer just keeps repeating the same mistakes. When
it comes to the question of wine and breast cancer, most studies still get it
wrong.
That’s one reason why I can’t help but be a little bit
cynical every October, when pink ribbons start sprouting everywhere, from
lapels to football jerseys to cereal boxes. Increased awareness is laudable, but
I wonder if these efforts do more to make us feel good than they do to actually
make a difference for women with breast cancer. Case in point: the Komen
Foundation, with its trademarked “for the cure” campaigns, reportedly spends
less than a fifth of funds on research support to find a cure.
Advocates for breast cancer victims can’t be blamed for the
misunderstandings about wine and cancer, and it’s hard to criticize the
researchers - whose intentions are noble – but perspective is lacking. The
Komen foundation wouldn’t even accept funds from a charitable wine auction I
was involved in a few years ago when we approached the local chapter with the
idea of making them a beneficiary. So we have this crazy situation where a
breast cancer foundation won’t accept wine money, which may be a good thing
because they don’t allocate much of it for research anyway.
Here’s the fundamental problem: When you do a study to
identify which lifestyle factors are related to breast cancer (or anything
else), of necessity you rely on self-reported questionnaires. With the question
of drinking, there is a well-known under-reporting tendency so what subjects say they drink and what they actually
drink are often not the same. This results in heavy drinking being
mis-categorized as moderate drinking, with the implication that moderate
drinking is riskier than it is.
When it comes to type
of drinking, for example wine vs. beer or spirits, it becomes even murkier.
What is well known about wine drinking and other disease conditions is that a
pattern of a glass or two of wine with dinner on a daily basis is associated
with lower risk than for nondrinkers. But very few people in a given North
American population actually drink this way. What the studies do is ask about
drinking preferences; if someone says
they prefer wine with dinner, they may only do it occasionally, and sometimes
have no alcoholic beverage, sometimes other types of drinks, and in varying
amounts depending on circumstances. This makes it virtually impossible to know
what the actual role of wine might be, even accounting for the under-reporting
bias. No matter how large the study, or how long-term, it’s the same problem
only amplified.
It’s clear that heavy drinking of any type is associated
with higher risk, but what’s not as clear is how this extrapolates to low or
moderate drinking. Generally, studies infer that a drink a day increases breast
cancer risk by 10%, 2 drinks 20%, and on up. What this means (often
misunderstood) is this is a percentage of baseline risk; so if you are at
average lifetime risk of about 8 or 9 percent, a 10% increase is not 18 or 19%,
but somewhere around 10 percent overall.
(10% of 9% is 0.9%, so a 10% increase = 9.9%)
To put this in perspective it is helpful to consider that
heart disease dwarfs breast cancer as a cause of death in women, and there is
no question that moderate drinking (especially wine) associates with a lower
risk. The same is true for diabetes, osteoporosis, and Alzheimer’s. For most women, stopping drinking to reduce
breast cancer risk would result in an increased overall risk of premature death
and disability.
But even that doesn’t tell the whole story. I am not
convinced that moderate wine drinking contributes to even a low risk of breast
cancer for the average woman. The definitive way to answer the question would
be to study a population of women who only drink red wine, and in moderation as
an integral part of their lifestyle. There are not very many of these studies
because there are not many such populations anymore, but there is some good data.
The best of these studies was done in Bordeaux a few years ago (1), and the
conclusion was that wine drinkers had a
substantially lower rate of breast cancer than nondrinkers.
Why should this be the case? For alcohol and breast cancer,
it took years for a plausible cause-effect relationship to be put forth, and
the best hypothesis is that it changes estrogen metabolism. Higher estrogen
translates to greater risk of certain types of breast cancers. These types,
known as estrogen-receptor positive (ER+), are often treated with drugs called
aromatase inhibitors, which ramp down estrogen production. Red wine, as it
turns out, is a natural aromatase inhibitor.
So forgive me if I don’t sport a pink ribbon, but I wish we
had more efforts like the former Cleavage Creek Winery, which used profits to
directly fund research at institutions like the Fred Hutchinson Cancer Research
Center and Bastyr Naturopathic University in Seattle, bypassing “Big Pink.” Founded by the late California winemaker Budge
Brown after losing his wife of 48 years to breast cancer, Cleavage Creek
donated more than $90,000 before the winery closed. So I say please do have a
glass of red wine and toast to all those who are doing so much to save and
improve women’s lives.
1. Bessaoud F, Daurès JP. Patterns of alcohol
(especially wine) consumption and breast cancer risk: a case-control study
among a population in Southern France. Ann Epidemiol. 2008 Jun;18(6):467-75.
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