Negative effects of alcohol

Alcohol can disrupt hormones, impair brain function and memory, damage cells, increase cancer risk, and contribute to cycles of lower mood and further drinking.

1. Testosterone-to-estrogen conversion: Alcohol can increase the conversion of testosterone to estrogen. In men, altered hormone ratios may contribute to lower sex drive, increased fat storage, and breast-tissue growth (gynecomastia). 1

2. Prefrontal activity and memory: Alcohol suppresses prefrontal circuits involved in planning and impulse control, which can increase impulsive behavior. It also suppresses networks involved in forming and storing memories, contributing to forgetfulness and blackouts. 2

3. Cell toxicity: Ethanol is toxic and causes substantial cellular stress and damage. The episode’s summary of the evidence ranks zero alcohol as healthier than low-to-moderate consumption, which in turn is healthier than moderately high-to-high consumption. 3 4

4. DNA changes and cancer risk: Alcohol’s toxic metabolites can alter DNA methylation and gene expression. The estimated breast-cancer risk increase is 4–13% for each 10 grams of alcohol consumed. Folate and B12 may partly reduce the added risk, but they do not eliminate it or guarantee protection. 5 6

5. Mood and repeated drinking: Alcohol can initially make mood circuits more active, contributing to feeling good and becoming talkative; as its effects wear off, serotonin activity and mood can drop, prompting some people to drink again to try to restore that feeling. 7

6. Occasional use: For most people who are of legal drinking age and not in a stage of brain development, one or two drinks every three or four weeks or about once a month was described as unlikely to cause major health concerns. 8