Cancer risk is increased because of the ethanol in alcohol, irrespective of the type of alcoholic beverage. Ethanol, the chemical in alcoholic beverages that induces the physical and mental responses experienced with alcohol use, is also a Group 1 carcinogen.
Alcohol use and cancer have a dose-response relationship; the more alcohol consumed over time, the higher the risk. The relationship is not a straight line, but shows upward curvature at higher drinking levels over time; the relationship appears to be consistent for women and men.
Although alcohol consumption probably decreases the risk of kidney cancer, there is no evidence for recommending alcohol consumption to protect against cancer. Even low levels of alcohol consumption can increase cancer risk. Evidence shows there is no threshold (or safe limit) of alcohol consumption and cancer risk, and that the more alcohol is consumed over a lifetime, the greater the risk of developing alcohol-related cancers.
There are a number of plausible biological mechanisms linking alcohol to cancer, such as:
- damaged DNA due to the acetaldehyde produced when alcohol is metabolised;
- increased oestrogen levels, which are associated with breast cancer;
- alcohol acting as a solvent for other carcinogens; and
- altered folate metabolism, affecting cell function.
The overall evidence to date suggests that alcohol is not a risk factor for kidney cancer, non-Hodgkin's lymphoma and bladder cancer. For lung cancer, the evidence is inconsistent or insufficient to conclude causality and the studies generally do not adequately control for the effects of smoking. For other cancers, evidence of an association between alcohol consumption and cancer risk is generally limited or inconsistent.
Table 2. Evidence of a link between alcohol and cancer type
|Type of cancer||Association with alcohol||Level of risk of causality|
|Breast (postmenopausal)||Increases risk||Convincing|
|Breast (premenopausal)||Increases risk||Probable|
|Bladder||Insufficient evidence of relationship|
Smoking and alcohol: synergies for high risk
Smoking and alcohol together have a synergistic effect on upper gastrointestinal and aero-digestive cancer risk, meaning the combined effects greatly exceed the risk from either one alone. It has been estimated that over 75% of cancers of the upper aero-digestive tract in developed countries can be attributed to this effect. For example, compared non-smoking non-drinkers, the approximate relative risks for developing mouth and throat cancer are up to seven times greater for those who use tobacco, up to six times greater for those who use alcohol, and 35 times greater for those who are regular heavy users of both tobacco and alcohol.
Alcohol has an independent effect on the risk of oral, pharyngeal, laryngeal and oesophageal cancers, but it is its synergistic effect with smoking that is most significant.
See the Tobacco control chapter of the National Cancer Prevention Policy for more information.
Alcohol and hepatitis B infection
Alcohol and hepatitis B virus infection may exert a joint effect on cancer of the liver. This is of particular concern in Aboriginal and Torres Strait Islander populations where hepatitis B is endemic, with data suggesting that liver cancer incidence and mortality rates are 3.5 to 3.6 times higher for Aboriginal and Torres Strait Islander males than for other Australian males. It highlights an important area for further investigation and action.
Alcohol and weight gain
As well as being a direct cause of several cancers, alcohol consumption may indirectly increase cancer risk by contributing to obesity and overweight, which are linked by convincing evidence to cancers of the oesophagus, pancreas, liver, bowel, breast (in post-menopausal women), endometrium and kidney. There is also probable evidence that body fatness is a cause of cancers of the mouth, pharynx, larynx, stomach, gallbladder, ovary and prostate. (Convincing and probable are the highest levels of evidence as determined by the World Cancer Research Fund and American Institute for Cancer Research and denote that the relationship is causal or probably causal in nature.)
The relationship between alcohol consumption and body weight and fat is complex and appears to vary with sex and drinking pattern. From a nutritional viewpoint, alcoholic drinks represent ‘empty kilojoules’ - meaning they are high in kilojoules but low in nutritional value, especially when added to sugary mixer drinks. Alcohol itself has a comparatively high energy content (29 kilojoules per gram) compared with other macronutrients.
If people drink alcohol in addition to their normal dietary intake – that is, without a compensatory reduction in energy intake – they are liable to gain weight. Alcohol provides extra kilojoules, and slows fat and carbohydrate oxidation. On the other hand, if drinking replaces healthy eating patterns, it can lead to nutritional deficiencies and serious illness.
Perceived health benefits of alcohol: the evidence
Evidence shows there is no threshold (or safe limit) of alcohol consumption and cancer risk and that the more alcohol is consumed over a lifetime, the greater the risk of developing alcohol-related cancers. There is evidence that alcohol is probably protective for kidney cancer and very moderate consumption (no more than one standard drink a day) may help to protect against pancreatic cancer.
The potential benefit of light to moderate alcohol consumption on cardiovascular disease is the subject of ongoing scientific debate. A number of population studies, including a 2011 systematic review have suggested light to moderate alcohol consumption may reduce the risk of cardiovascular disease. However, other reviews have suggested unmeasured confounding in epidemiological studies on alcohol and heart disease is widespread and that randomised controlled trials may be the only way to obtain more consistent evidence about the effects of moderate alcohol consumption on cardiovascular disease risk.
Conclusive evidence shows higher levels of alcohol consumption confer no cardiovascular health benefits. The 2011 review that suggested moderate alcohol consumption may reduce cardiovascular disease risk also linked higher alcohol consumption levels with an increased risk of stroke. Neither the World Health Organization nor the National Heart Foundation of Australia recommend consuming red wine or any other alcoholic beverage to prevent cardiovascular disease.
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