Alcohol and Your Body: What the Evidence Now Says About Safe Limits
For decades the public message about alcohol was that moderate drinking was protective. That position has weakened considerably, and the honest current summary is that less is better and there is no clearly established risk-free level, particularly for cancer.
Where the old story came from
Early observational studies showed that moderate drinkers had lower cardiovascular mortality than abstainers. The problem was the comparison group: “abstainers” included people who had stopped drinking because they were already ill, plus former heavy drinkers. When studies corrected for this, and when genetic studies looked at people whose alcohol metabolism is naturally lower, the apparent benefit largely disappeared.
Any small cardiovascular benefit is also set against alcohol’s clear, dose-dependent increase in cancer risk, which begins at low intake.
What a standard drink is
A standard drink contains about 10 g of pure alcohol:
- 330 ml of beer at 5 percent
- 150 ml of wine at 12 percent
- 45 ml of spirits at 40 percent
Home pours are typically much larger than these. Most people substantially underestimate their intake, so counting actual bottles rather than “a couple of drinks” is more informative.
Effects by organ
Liver. Fatty liver develops in most heavy drinkers and is reversible. Alcoholic hepatitis can be severe. Cirrhosis is irreversible, and liver damage is silent until advanced. Women develop liver damage at lower intakes than men.
Cancer. Alcohol is a Group 1 carcinogen. Increased risk of cancer of the mouth, pharynx, larynx, oesophagus, liver, colon, rectum and breast. Breast cancer risk rises measurably from around one drink a day, which is not widely known. Risk multiplies with tobacco.
Heart. Raises blood pressure. Causes atrial fibrillation, including from single heavy episodes. Causes cardiomyopathy in heavy use. Raises triglycerides.
Brain. Impairs memory and decision-making acutely; chronic heavy use causes brain shrinkage, thiamine deficiency and Wernicke-Korsakoff syndrome, and raises dementia risk. Alcohol is a depressant and worsens anxiety and depression despite feeling like it helps.
Sleep. Alcohol shortens time to fall asleep and then fragments the second half of the night, suppresses REM sleep, and worsens sleep apnoea. People who use it to sleep sleep worse.
Pancreas. Acute and chronic pancreatitis.
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Gut. Gastritis, ulcers, reflux, and malabsorption.
Weight. 7 calories per gram, with no nutritional value, and it disinhibits eating.
Reproduction. Reduces fertility in both sexes. No amount is known to be safe in pregnancy; fetal alcohol spectrum disorder is entirely preventable.
Interactions. Dangerous with paracetamol in high doses, sedatives, opioids, some antibiotics, and many other medications.
Risk thresholds
Guidelines vary. A commonly used low-risk limit is no more than 14 units a week for both men and women, spread over at least three days, with several alcohol-free days. Canada’s 2023 guidance went further, describing risk as low below two drinks a week and increasing thereafter.
Binge drinking, meaning several drinks in one session, carries its own risks independent of the weekly total: injury, arrhythmia, acute pancreatitis and alcohol poisoning.
Signs intake has become a problem
- Difficulty stopping once you start
- Drinking more to get the same effect, meaning tolerance
- Needing a drink to steady yourself, or morning drinking
- Withdrawal: tremor, sweating, anxiety, nausea when not drinking
- Drinking despite problems it causes at work, at home or with health
- Failed attempts to cut down
- Concealing intake, drinking alone, or irritation when asked about it
- Memory blackouts
- Neglecting responsibilities or interests
Family concern is a stronger signal than self-assessment. Screening tools such as AUDIT-C are brief and available from any doctor.
Cutting down
- Count accurately for two weeks first, in standard drinks
- Set a specific weekly limit and alcohol-free days, and put them in a calendar
- Switch to smaller measures and lower-strength drinks
- Alternate with water
- Avoid drinking on an empty stomach
- Do not keep alcohol at home
- Identify triggers: stress, specific company, time of day, particular situations
- Find a substitute ritual for the time of day you usually drink
- Tell someone, which substantially improves success
- Expect sleep to improve after about a week, and energy and mood after two to four
Important safety point: people with physical dependence must not stop abruptly. Alcohol withdrawal can cause seizures and delirium tremens, which can be fatal. Medically supervised detoxification with benzodiazepines and thiamine is needed. If you drink daily, heavily, or get shaky without a drink, speak to a doctor before stopping.
Treatment that works
Brief interventions from a doctor are effective for hazardous drinking. For dependence: supervised detoxification, relapse-prevention medication such as naltrexone, acamprosate or disulfiram, psychological therapy, and mutual support groups. Treating the depression or anxiety underneath, which is very common, improves outcomes substantially.
Relapse is part of the pattern for many people and is a reason to resume treatment rather than to abandon it.
This is general information and a sensitive topic. If you are worried about your own or someone else’s drinking, speak to a doctor; do not stop heavy daily drinking abruptly without medical advice.