Alcohol consumption has been tied to increased risk of breast cancer in numerous studies. It is one of the most well-documented modifiable risk factors for breast cancer. While it has been thought that one drink per day might be a safe level of consumption, recent studies indicate that even this level of intake could be unsafe.
Now a new study has reported that red wine might be a safe choice since it can inhibit aromatase, the production of estrogen from androgens within the body. The question remains, how much wine is safe for breast cancer survivors and those at high risk for breast cancer?

Wine compared to other alcohol

The question of whether wine consumption, and red wine in particular, is safer than other types of alcoholic drinks has been addressed in several population studies. Almost no studies have found a difference in breast cancer risk based type of drink (beer, wine, hard liquor). The increase in breast cancer risk derives from the ethanol content of alcoholic drinks. The other compounds found in drinks, including the polyphenols in beer and wine, do not appear to greatly influence the risk.
For example, one U.S. study that included 6,327 breast cancer patients and 7,558 cancer-free controls reported that women who consumed 14 or more drinks per week, regardless of type (red wine, white wine, liquor or beer) were 24% more likely to have breast cancer compared to women who did not drink any alcohol. The authors concluded that neither red nor white wine appear to have any benefits with respect to breast cancer risk and that red and white wine increase breast cancer risk equally. On the other hand, one French study found that moderate wine drinking reduced cancer risk, although the results were not analyzed according to type of wine.

Evidence from the latest study

The new study referenced at the beginning of this news article was designed to investigate whether red wine is a nutritional aromatase inhibitor in premenopausal women. Grapes, grape juice, and red (but not white) wine, contain phytochemicals such as procyanidin B dimers and resveratrol that are capable of suppressing aromatase. The study included 36 women with average age 36. The authors used a cross-over study design in which the women were assigned to drink either 8 oz. (237 mL) of red wine (Cabernet Sauvignon) each day for once month followed by white wine (Chardonnay) for one month, or the reverse schedule. Blood was collected twice during each month to assess levels of estradiol (E2), estrone (E1), sex hormone binding globulin, androstenedione, total and free testosterone, luteinizing hormone, and follicle stimulating hormone (FSH).
Participants had higher free testosterone and luteinizing hormone, and lower sex hormone binding globulin levels when drinking red wine compared to white wine. E2 levels were also lower during red wine drinking periods, but the difference was not statistically significant. FSH was not significantly higher during the red wine drinking period. The authors conclude that the data suggests that red wine is a nutritional aromatase inhibitor, which may explain the observation that red wine does not appear to increase breast cancer risk.
This study had few participants and the results are not compelling. The findings concerning estrogen did not reach statistical significance, although it is clear that consuming red wine did result in a different hormonal profile than consuming white wine. A larger study is needed.

Influence of wine drinking on breast cancer recurrence

A major 2010 prospective study, which included 1,897 breast cancer patients from Kaiser Permanente Northern California, reported that moderate alcohol consumption was associated with increased breast cancer recurrence. The majority of the women (89%) drank wine. Compared with abstinence from alcohol, drinking at least 6 g/day of alcohol was found to be associated with 1.35 times the risk of breast cancer recurrence. The risk of recurrence was higher among postmenopausal and overweight women. The authors concluded that consuming three to four alcoholic drinks or more per week after a breast cancer diagnosis may increase risk of breast cancer recurrence.

The bottom line

It appears unlikely that drinking red wine reduces the risk of breast cancer or breast cancer recurrence. Consuming several drinks at once may be more risky than limiting consumption to one drink per session. Women who are fast metabolizers of alcohol (and therefore “can't hold their liquor”) have a higher risk of breast cancer from alcohol consumption than slow metabolizers. Based on the evidence to date, a glass of wine with food every other day might be a safe level of consumption. Some alcohol-free red wines are available that might also be a good substitute for some women.