Alcohol and breast cancer: An overview
There’s a good deal of indirect evidence linking higher intakes of alcohol to increased risk of breast cancers … primarily, the estrogen-dependent type that constitutes most cases.
What about the risk of alcohol to women who already have breast cancer?
A Swedish team looked at this question and found that one small drink per day seemed to reduce women’s survival rates … but one-half drink per day was linked to a lower risk of death from other causes (Harris HR et al. 2012).
How much alcohol presents a risk?
A Swedish team recently found that one small drink per day seemed to reduce women’s survival rates over a 10-year period … but one-half drink per day was linked to a lower risk of death from other causes (Harris HR et al. 2012).
How much alcohol presents a risk?
Women in the Swedish study who drank 10 grams of alcohol per day (about 0.75 to 1 drinks) or more were 36 percent more likely to have died from breast cancer. Those who consumed 3.4 to 9.9 grams per day had a one-third (33 percent) lower risk of dying from any other cause, compared with non-drinkers.
And researchers in Italy concluded this about the dose-related risk of alcohol:
“While consumption of fewer than 3 alcoholic drinks per week is not associated with an increased risk of breast cancer, an intake of 3 to 6 drinks per week might yield a small increase in risk.” (Pelucchi C et al. 2011)
Why would alcohol promote breast cancer?
The findings of a study from the Kaiser Permanente Center for Health Research in Portland, Oregon suggest three answers:
Alcohol increases levels of endogenous (internally produced) estrogens, which are known risk factors for estrogen-dependent breast cancers.
Products of alcohol metabolism are known to be toxic and may cause DNA modifications that lead to cancer.
Alcohol promotes inflammation, and mounting evidence suggests that antioxidant intake may reduce alcohol-associated breast cancer risk. This is because antioxidants neutralize the reactive oxygen species (free radicals) created as byproducts of alcohol metabolism and inflammation alike.
As to inflammation, a mouse study from the University of Kentucky College of Medicine showed that alcohol “up-regulated” the expression of pro-inflammatory signaling molecules (MCP-1 and CCR2) that appear to promote tumor growth, spread, and blood supply (Wang S et al. 2011).
Affirming that this effect on genes has real consequences, drinking alcohol increased the blood supply to the rodents’ tumors (angiogenesis) and promoted the growth and spread (metastasis) of their breast cancer cells.
The intriguing results of a small human study suggest that red wine may be an exception to the rule that alcohol consumption heightens the risk of developing breast cancer.
Study finds red wine lowers estrogen levels
The new study was led by doctors from Cedars-Sinai Medical Center, and included colleagues from the University of Southern California, and Connecticut’s Hartford Hospital (Shufelt C et al. 2012).
They recruited 36 premenopausal women, who were randomly assigned to drink either (red) Cabernet Sauvignon or (white) Chardonnay wine daily for almost a month (one menstrual cycle).
After one month, the women switched to the other type of wine for another menstrual cycle.
Blood samples were collected twice each month to measure the women’s hormone levels.
The results showed that drinking eight ounces of red wine nightly for about a month slightly lowered women’s estrogen levels while raising their testosterone levels.
Drinking white wine had no effect on estrogen levels. This difference was attributed to the polyphenol “antioxidants” that abound only in red wine, which come from grape seeds and skins.
Certain grape polyphenols found in red wine – isoflavone phytoestrogens, flavones, and procyanidins – are known to act as “aromatase inhibitors” which means that they prevent the conversion of androgens (“male” hormones) to estrogen.
In fact, aromatase-inhibiting agents are used to treat breast cancer, because they raise testosterone levels and lower levels of various forms of estrogen: estradiol, estrone, and sex hormone binding globulin (SHBG).
The Cedars-Sinai study affirms the idea that red wine exerts aromatase-inhibiting effects … at least in premenopausal women.
As the authors wrote, “These data suggest that red wine is a nutritional AI [aromatase inhibitor] and may explain the observation that red wine does not appear to increase breast cancer risk.” (Shufelt C et al. 2012)
The researchers called their findings encouraging, saying women who occasionally drink alcohol might want to reassess their choices.
“If you were to have a glass of wine with dinner, you may want to consider a glass of red,” said study co-author Chrisandra Shufelt, M.D. “Switching [from white wine or other alcoholic drinks] may shift your risk.” (CSMC 2012)
Importantly, the investigators said the change in hormone patterns suggested that red wine may stem the growth of cancer cells, as has been shown in test tube studies.
As co-author Glenn D. Braunstein, M.D., said, “There are chemicals in red grape skin and red grape seeds that are not found in white grapes that may decrease breast cancer risk.” (CSMC 2012)
Large-scale studies will be needed to see whether red wine actually alters breast cancer risk. And until those larger studies are done, he would not recommend that a non-drinker begin to drink red wine.
The U.S. CDC recommends that women average no more than one drink a day, and that men average no more than two drinks daily.
The UK health authorities just recommended that everyone abstain at least two days out of the the week.
However, in response to that guidance, the head of the CDC alcohol division told NPR today that his agency is more concerned about “binge” drinking – which he defined as having more than three (women) to five (men) drinks in a short period.
Surprisingly, a recent CDC study found that older adults do more binge drinking than among young adults.
Coronado GD, Beasley J, Livaudais J. Alcohol consumption and the risk of breast cancer. Salud Publica Mex. 2011 Oct;53(5):440-7.
Harris HR, Bergkvist L, Wolk A. Alcohol intake and mortality among women with invasive breast cancer. Br J Cancer. 2012 Jan 3. doi: 10.1038/bjc.2011.561. [Epub ahead of print]
Holcomb VB, Hong J, Nunez NP. Exogenous estrogen protects mice from the consequences of obesity and alcohol. Menopause. 2012 Jan 6. [Epub ahead of print]
Pelucchi C, Tramacere I, Boffetta P, Negri E, La Vecchia C. Alcohol consumption and cancer risk. Nutr Cancer. 2011 Oct;63(7):983-90. Epub 2011 Aug 24.
Shufelt C, Merz CN, Yang Y, Kirschner J, Polk D, Stanczyk F, Paul-Labrador M, Braunstein GD. Red Versus White Wine as a Nutritional Aromatase Inhibitor in Premenopausal Women. J Womens Health (Larchmt). 2011 Dec 7. [Epub ahead of print]
Wang S, Xu M, Li F, Wang X, Bower KA, Frank JA, Lu Y, Chen G, Zhang Z, Ke Z, Shi X, Luo J. Ethanol promotes mammary tumor growth and angiogenesis: the involvement of chemoattractant factor MCP-1. Breast Cancer Res Treat. 2011 Dec 9. [Epub ahead of print]