Red wine has been shown to help prevent and inhibit the development of breast cancer in mice. Red wine can inhibit aromatase, the production of estrogens from androgens within the body. It has also been shown to limit the toxic skin effects of radiation therapy for breast cancer. However, alcohol consumption has also been found to be associated with increased risk of breast cancer in the general population. Do the potential benefits of drinking red wine outweigh its harmful effects?

Effects of alcohol on breast cancer risk and recurrence

Like grapes, red wine is an excellent source of resveratrol and other polyphenols that have been shown to counteract the development of breast cancer. Resveratrol has the ability to suppress proliferation of breast cancer cells and promote cell death, as well as inhibiting aromatase, which is important for reducing growth-stimulatory effects in estrogen-dependent breast cancer. Resveratrol has also been shown to enhance the effectiveness of radiation treatment.
Alcohol consumption is positively correlated with breast cancer risk, particularly hormone receptor positive (ER+/PR+) and lobular breast cancer. The association between alcohol intake and increased breast cancer risk is strongest in postmenopausal women.
Alcohol has also been shown to increase risk of recurrence in breast cancer survivors. A major 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.
On the other hand, there is some limited evidence that drinking wine may protect BRCA1 mutation carriers against breast cancer.

How much red wine is safe for breast cancer survivors?

Drinking red wine is on balance harmful for breast cancer patients and those at relatively high risk for breast cancer. The potential benefits of resveratrol and other chemopreventative substances appear to be overwhelmed in the body by the cancer-promoting effects of the alcohol in red wine. Red grapes, blueberries, blackberries and cranberries are good alternate sources of resveratrol. Also, some alcohol-free red wines are available that might be a good substitute for some women.
Other spices and foods such as turmeric, parsley, holy basil, garlic, onions, and mangoes have also been found to protect against radiation damage. In particular, the curcumin in turmeric has been found in mouse models to effectively protect skin from radiation damage, while at the same time sensitizing breast cancer cells to radiation and making them more susceptible to its effects.
For breast cancer patients, those in remission and those at high risk for breast cancer, the cancer promoting properties of red wine outweigh its potential benefits (including preventing cardiovascular disease). Drinking purple grape juice and using red wine in cooking is preferable to drinking red wine. Based on the evidence to date, a glass of red wine with food every other day might be a relatively safe level of consumption.
Below are links to recent studies on this topic. For a more complete list of studies, please click on alcohol.