Humans have been drinking beverages containing alcohol for well over a thousand years. Mild to moderate acute alcohol intake has a euphoric effect probably caused by release of dopamine in the brain. At lower blood levels alcohol promotes social interaction, which is likely why it has such a long history of use in human society. The actual effect of alcohol on the brain is complex and not well understood. Brain function is a delicate balance of excitatory and inhibitory neurotransmitters. Alcohol alters this balance in a complex way that is difficult to measure and characterize.
Addiction to alcohol occurs in some people. About half of alcohol addiction is genetically determined. Other causes include use to alleviate mental disorders such as anxiety or depression or psychosocial stress. Physicians used to use the term alcoholism to refer to alcohol addiction, but now the correct term is alcohol use disorder. This can range from mild to severe and is defined by NIH as a medical condition characterized by an impaired ability to stop or control alcohol use despite adverse social, occupational, or health consequences. Severe alcohol use disorder has major health and social consequences for both individuals and society.
In this post I’m not going to write further about alcohol use disorder. That is a subject unto itself. Instead I’m going to focus this post on the health effects of alcohol use that does not meet the definition of alcohol use disorder, so called “social drinking.”
Physicians used to say that a safe level of alcohol use was 2 drinks a day for a male and 1 drink a day for a female. Now physician advice is that no level of alcohol use is safe. Alcohol use has been shown to increase the risk of many cancers as well as heart disease. The real question is how big is the risk for these conditions and at what level of alcohol intake.
Measuring alcohol use
The term “drink” is not very precise. I once had a patient who insisted she only had one drink a day. Her one drink consisted of a 12 ounce glass of vodka. The UK has developed a different measure of alcohol intake called units of alcohol. One unit of alcohol is the amount an average person can metabolize completely in 1 hour. That amount is 10 cc (1/3 of an ounce) or 8 grams of pure alcohol. Here is a list of the number of units in beer, wine and cocktails:
- Four ounce glass of wine (red or white) – 1.5 units
- Six ounce glass of wine (red or white) – 2.1 units
- Eight ounce glass of wine (red or white) – 3 units
- Low alcohol pint of beer – 2 units
- High alcohol pint of beer – 3 units
- Bottle of beer – 1.7 units
- Cocktails – 2.5-3 units
If you drink alcohol, add up the number of units you drink per week. The greater the number of units per week, the higher the risk, which I will quantify below. Be aware that most of these risks are very small. There are quite a few people who don’t drink at all or drink only rarely. These people simply don’t have any desire to drink alcohol or don’t like the way it makes them feel. These essentially non-drinkers form the comparison group for the risk of drinking alcoholic beverages.
Risk of Alcohol Use Disorder
The vast majority of social drinkers do not develop alcohol use disorder, but people who have a family history of alcohol use disorder are at greater risk if they start social drinking. Social drinking is also not a good idea for people with severe anxiety or depression.
Risk of Cancer
Drinking alcohol increases the risk of certain cancers, particularly colorectal cancer, breast cancer, liver cancer, esophageal cancer, and throat cancer. The total absolute cancer risk for drinking greater than 14 units of alcohol per week from age 25 to 85 is 4% for men and 5.4% for women. That translates to an annual risk of .0667% for men and .09% for women. To put that risk in perspective, the annual risk of death from a car accident in the US is .013%. and the annual injury risk from a car accident is 1%.
Risk of Death
In a large study in the UK, risk of death from all causes was associated only with drinking more than 42 units of alcohol per week.
Accelerated Ageing
Recent studies have looked at two measures of biologic ageing. At the end of each chromosome are structures called telomeres. It is known that these telomeres shorten as a person ages. The other measure is called epigenetics. These are non-DNA changes that are heritable. Some of these epigenetic changes increase as a person ages. Recent studies show an association between alcohol intake and these biologic ageing changes. There seems to be a dose response relationship. The more alcohol you drink, particularly liquor as opposed to beer and wine, the more your telomeres shorten and epigenetic changes accumulate. This association was most marked in people with alcohol use disorder. There was little association for light to moderate social drinkers. Association does not mean causation, however the researchers controlled for other things that might account for these changes like smoking, diabetes, and others. It is possible and even likely that these ageing changes were caused by alcohol intake.
Risk of Accidents
Even mild to moderate drinking impairs reaction time so driving after drinking any amount of alcohol is not a good idea. Heavier drinking causes more impairment of motor function and increases risk of accidents such as falls. Driving after heavier drinking markedly increases the risk of auto accidents, which can injure or kill others as well as the one who is drinking. Anyone who drinks any amount of alcohol outside the home should have a designated driver who agrees not to drink, or call Uber, Lift, or a taxi to be driven home.
Sleep Disturbance
Drinking alcohol, particularly later in the evening can cause sleep disturbance with early awakening and difficult getting back to sleep. This can occur even with light to moderate drinking.
Bottom Line
Drinking alcohol at all does increase the risk of cancer and heart disease. The annual risk is dose related, but is still very small for light and moderate drinkers (14-21 units per week) The risk of illness and death and accelerated ageing is higher for heavier drinkers, but still relatively small. Drinking alcohol later in the evening often causes sleep disturbance. This can usually be avoided by timing drinking alcohol in the late afternoon or early evening. The risk of cancer and heart disease from drinking is low but not zero. People who choose to drink alcohol are accepting that risk. Driving is not a good idea for any level of alcohol intake. Light to moderate drinking is definitely less risky than heavier drinking, which includes association with accelerated ageing as well as increased risk of auto accidents. These risks are still fairly small. People who have alcohol use disorder should seek professional help and strive to be completely abstinent from alcohol.