The International Agency for Research on Cancer has long stated that consuming a glass of alcohol a day (equivalent to 10 grams of alcohol) in women, both before and after menopause, has been shown to increase breast cancer risk 7-10%. This effect arises because breast tissue is more susceptible to carcinogenic effects caused by alcohol than other tissues or organs.


Alcohol Increases Breast Cancer Risk



The riskiest periods to drink alcohol that increases breast cancer risk

Various studies suggest that women who consume alcohol early on have an increased lifetime risk of developing breast cancer. The most alcohol consumption period that causes breast cancer is between menarche and the first pregnancy, although this risk is accumulative throughout the woman's life. This is important, considering that almost 50% of women of reproductive age consume alcohol, and 15% drink 4-5 glasses at a time.

The consuming alcohol before lactation also is considered the most at risk of increasing the incidence of breast cancer because alcohol consumption at puberty causes morphological changes in the breast glands. Meanwhile, in the period after puberty, breast tissue proliferates very rapidly until pregnancy.

Other studies also support the claim that alcohol consumption in the period before the first pregnancy increases breast cancer risk. The risk of breast cancer increased by 34% in women who consumed ≥15 grams of alcohol (approximately 1.5 glasses per day) in a cohort with 91,005 subjects.

The period between menarche and the first pregnancy in women who consumed 10g of alcohol per day also influenced breast cancer risk. Between the ages of 10-14 years, between menarche and first pregnancy, the risk of breast cancer increases by 14%. Whereas in the range ≥ 15 years, the risk increased by 25%.



The most risk alcohol drinking pattern of getting breast cancer

Consuming >4 glasses of alcohol at a time (binge drinking) has a higher risk of getting breast cancer because of high alcohol levels in the blood when drinking several glasses at one time. This high alcohol content causes activation of different metabolic pathways. The breast cancer risk in women who binge drink is 21% higher than in women who do not drink alcohol.


Mechanism of Carcinogenesis in Alcohol Consumption

How can alcohol cause breast cancer?
During pre– and postmenopausal phases,  alcohol consumption may increase estrogen levels in the blood through decreased steroid degradation and increased aromatase activity. Prolonged exposure to estrogen has been shown to increase breast cancer incidence in humans. The products of alcohol metabolism in breast tissue also play a role in carcinogenic processes. The carcinogenesis process can occur in 2 ways:
  1. Estrogen receptor (ER) -α-independent, which is genotoxic
  2. ER-dependent, which increases the transcription activity of estrogen receptors. It is more dominant in hormone receptor-positive breast tumors.
Alcohol is carcinogenic because of its genotoxic effect (damages DNA). In the human body, alcohol is converted to acetaldehyde by the enzyme alcohol dehydrogenase. Acetaldehyde will bind to DNA and proteins, causing mutations and crosslinks, and even chromosomal abnormalities. Also, acetaldehyde inhibits the body's natural repair mechanism against oxidative DNA damage.

Several new mechanisms that explain the carcinogenic nature of alcohol include:
  • the epithelial-mesenchymal transition (EMT), which is the increased attachment of cancer cells to fibronectin, 
  • and epigenetic regulation of gene expression associated with folate metabolism disorders.


Risky Alcoholic Beverages

The effect of alcoholic beverages on breast cancer risk varies, depending on the type of drink. Although all alcoholic drinks can increase breast cancer risk, wine is considered the most at risk of causing breast cancer, according to several studies.

Red Wine

Red wine is considered a protective effect against cancer development because of its polyphenolic compounds derived from grape skins. The antioxidant, anti-inflammatory, and anticancer effects of polyphenols in red wine occur through various molecular and biochemical processes. One of the polyphenol compounds of concern is resveratrol, which can inhibit the DNA methyltransferase enzyme. This enzyme catalyzes DNA methylation and prevents epigenetic silencing of the BRCA1 tumor suppressor protein. However, several studies studying the effect of grapes on breast cancer found that grapes still increase breast cancer risk.

Beer

In addition to having very little resveratrol content and very limited absorption in the body, beer has been shown to increase breast cancer risk in women who consume 10 grams of beer (generally the equivalent of 1 glass) per day.




Summary
Consumption of alcoholic beverages increases the risk of breast cancer. The period of alcohol consumption that is considered the most at risk of causing breast cancer is between menarche and first pregnancy. This risk is higher in women with longer intervals between their first menstruation and first pregnancy. Wine is proven to increase breast cancer risk than other alcoholic drinks (beer, spirits). Prolonged exposure to the hormone estrogen is known to increase the incidence of breast cancer. Shorter exposure to estrogen (slow first menstruation, earlier pregnancy, and late menopause) is thought to reduce breast cancer risk.