Alcohol (also known as ethanol) has a number of effects on health. Short-term effects of alcohol consumption include intoxication and dehydration. Long-term effects of alcohol include changes in the metabolism of the liver and brain, several types of cancer and alcohol use disorder.[1] Alcohol intoxication affects the brain, causing slurred speech, clumsiness, and delayed reflexes. There is an increased risk of developing an alcohol use disorder for teenagers while their brain is still developing.[2] Adolescents who drink have a higher probability of injury including death.[2]
Even light to moderate alcohol consumption can have negative effects on health,[3][4][5] such as by increasing a person's risk of developing several cancers.[6][7] A 2014 World Health Organization report found that harmful alcohol consumption caused about 3.3 million deaths annually worldwide.[8] Negative effects are related to the amount consumed with no safe lower limit seen.[9] Some nations have introduced alcohol packaging warning messages that inform consumers about alcohol and cancer, as well as fetal alcohol syndrome.[10]
The median lethal dose of alcohol in test animals is a blood alcohol content of 0.45%. This is about six times the level of ordinary intoxication (0.08%), but vomiting or unconsciousness may occur much sooner in people who have a low tolerance for alcohol.[11] The high tolerance of chronic heavy drinkers may allow some of them to remain conscious at levels above 0.40%, although serious health hazards are incurred at this level.
Alcohol also limits the production of vasopressin (antidiuretic hormone) from the hypothalamus and the secretion of this hormone from the posterior pituitary gland. This is what causes severe dehydration when alcohol is consumed in large amounts. It also causes a high concentration of water in the urine and vomit, and the intense thirst that goes along with a hangover.
The ASCO statement, published in the Journal of Clinical Oncology, cautions that while the greatest risks are seen with heavy long-term use, even low alcohol consumption (defined as less than one drink per day) or moderate consumption (up to two drinks per day for men, and one drink per day for women because they absorb and metabolize it differently) can increase cancer risk. Among women, light drinkers have a four percent increased risk of[breast cancer, while moderate drinkers have a 23 percent increased risk of the disease.
Clearly, the greatest cancer risks are concentrated in the heavy and moderate drinker categories. Nevertheless, some cancer risk persists even at low levels of consumption. A meta-analysis that focused solely on cancer risks associated with drinking one drink or fewer per day observed that this level of alcohol consumption was still associated with some elevated risk for squamous cell carcinoma of the esophagus (sRR, 1.30; 95% CI, 1.09 to 1.56), oropharyngeal cancer (sRR, 1.17; 95% CI, 1.06 to 1.29), and breast cancer (sRR, 1.05; 95% CI, 1.02 to 1.08), but no discernable associations were seen for cancers of the colorectum, larynx, and liver.