Health effects of alcohol

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, with increased risk of several types of cancer and alcohol use disorder. 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. Adolescents who drink have a higher probability of injury including death. Light alcohol consumption was misclassified as possibly healthy in the past by several studies, but evidence shows that even minimal to light alcohol consumption can have negative effects on health, such as by increasing a person's risk of developing several cancers. A 2014 World Health Organization (WHO) report found that harmful alcohol consumption caused about 3.3 million deaths annually worldwide. Negative effects are related to the amount consumed with no safe lower limit seen. Some nations have introduced alcohol packaging warning messages that inform consumers about alcohol and cancer, as well as fetal alcohol syndrome. In modern medicine, the only possible beneficial uses of alcohol are as a topical disinfectant, temporary emergency cure for alcohol withdrawal syndrome, and, as long as kept in strict moderation, positive social effects outweighing harm to the body. Practically no authorities recommend starting drinking for any positive effects. In January 2025, the surgeon general of the United States released an advisory describing a causal relationship between alcohol consumption and increased risk of seven different types of cancer, including colorectal cancer, liver cancer, and throat cancer. The advisory recommended updating the health warning label on alcohol-containing beverages in the United States to include a warning about the risk of cancer from consuming these beverages.

Short-term effects

The short-term effects of alcohol consumption range from a decrease in anxiety and motor skills at lower doses to unconsciousness, anterograde amnesia, and central nervous system depression at higher doses. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every cell in the body. The concentration of alcohol in blood is measured via blood alcohol content (BAC). The amount and circumstances of consumption play a large part in determining the extent of intoxication; for example, eating a heavy meal before alcohol consumption causes alcohol to absorb more slowly. Hydration also plays a role, especially in determining the extent of hangovers. After binge drinking, unconsciousness can occur and extreme levels of consumption can lead to alcohol poisoning and death (a concentration in the blood stream of 0.40% will kill half of those affected). Alcohol may also cause death indirectly, by asphyxiation from vomit. Alcohol disrupts normal sleep patterns thereby reducing sleep quality and can greatly exacerbate sleep problems. During abstinence, residual disruptions in sleep regularity and sleep patterns are the greatest predictors of relapse. Heavy alcohol consumption while in a hunger state can cause alcoholic ketoacidosis, a life-threatening metabolic derailment. 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. 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.

Long-term effects

According to the World Health Organization's 2018 Global Status Report on Alcohol and Health, there are more than 3 million people who die from the harmful effects of alcohol each year, which amounts to more than 5% of the burden of disease worldwide. The US National Institutes of Health similarly estimates that 3.3 million deaths (5.9% of all deaths) were believed to be due to alcohol each year. As per WHO June 2024 report on Alcohol, around 2.6 million deaths were caused by alcohol consumption in 2019 worldwide. Guidelines in the US and the UK advise that if people choose to drink, they should drink modestly. Even light and moderate alcohol consumption increases a person's cancer risk, especially the risk of developing squamous cell carcinoma of the esophagus, cancers of the mouth and tongue, liver cancer, and breast cancer. Using alcohol, especially together with tobacco, is a major risk factor for head and neck cancer. 72% of head and neck cancer cases are caused by using both alcohol and tobacco. This rises to 89% when looking specifically at laryngeal cancer.

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