Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems.
Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start. There is evidence that excessive consumption of alcoholic beverages or binge drinking is associated with increased morbidity and mortality from several forms of cancer. Low amounts of wine on the other hand, are not associated with the risk of any cancer site with the possible exception of breast cancer for women and cancers of upper gastrointestinal tract (GIT) such as the mouth and throat as well as the liver. An increased risk for the GIT cancers is observed with all alcoholic beverages, which is a linear relationship (the greater the amount, the higher the risk), and especially in combination with smoking.
With regards to breast cancer and alcoholic beverages, the research results vary widely since not only the amount of alcohol but also other co-factors as well as drinking pattern play an important role and have to be taken into consideration.
The majority of epidemiological studies, however, show a linear increase in the relative risk of breast cancer with an increasing dose of alcohol but the magnitude of the effect is small. An increased breast cancer risk is observed in women with additional co-factors such as genetic disposition, hormone replacement therapy (HRT), low folate intake, overweight and smoking.
A meta-analysis for example, examined the influence of hormones on breast cancer risk and found that alcoholic beverages (> 20g/d) might increase the breast cancer risk only among women who were concurrently using menopausal hormone therapy (HT) and /or having estrogen receptors positive tumors. These findings indicate that a hormone-related mechanism may mediate the relation between alcohol drinking and an increased breast cancer risk. Among women who had ceased using HT, the risk associated with 2 or more drinks per day was not apparent.
Another factor to be considered is folate intake. Several studies have shown an inverse relation between folate intake and cancer. Accordingly, some research results found a significant interaction between the consumption of alcoholic beverages and folate intake where alcohol seems to increase the risk significantly only for those individuals with low folate intake.
All the studies show that the knowledge about the causes of breast cancer is still very incomplete and as scientists from the National Institute on Alcohol Abuse and Alcoholism in the USA, recently pointed out, some other (possible confounding) factors have not been considered in the research relating the consumption of alcoholic beverages to breast cancer:
- In the epidemiological data provided, the intake of alcoholic beverages is usually under-reported by subjects (which could exaggerate the harm associated with light drinking).
- In most studies, the pattern of drinking (regularly and moderately vs. binge drinking with a similar total weekly alcohol consumption) as well as beverage type have generally not been taken into account. However, this aspect of drinking pattern is important given that binge drinking is associated with much higher blood alcohol concentrations and acetaldehyde accumulation (a known carcinogen) and production of free radicals (reactive oxygen species). Considering that the blood alcohol level may be the most important mechanism for effects on cancer risk, the pattern by which a woman consumes a given amount of alcohol is particularly relevant in interpreting associations.
- In addition, epidemiological studies usually provide data only for a short period of time, while the development of cancer may relate to exposures over many decades.
The authors concluded that based on scientific evidence, in post menopausal women, the increase in the risk of breast cancer, if there is any at all, is small..
The relationship between wine consumption and cancer is even more complex. It is not yet completely proven that wine drinkers have a lower risk for cancer than drinkers of other alcoholic beverages. However, epidemiological studies indicate a lower cancer risk for wine drinkers for most cancer sites compared to drinkers of other alcoholic beverages. Moderate wine intake may actually reduce the risk of oesophagus, thyroid, lung, kidney and colorectal cancers as well as Non-Hodgkin’s Lyphoma. To what extent differences in drinking pattern or certain beverage-specific ingredients are responsible still needs to be determined. Concerning breast cancer, there may also be a protective role for wine.
What might be a possible mechanism for the protective effect of wine? Damage to the DNA of cells by chemicals in the environment and food as well as by the physical environment can lead to cancer. Various experimental studies suggest that the phenolic compounds in wine may protect the DNA of cells of body tissues from damage or may stop the growth of cells with damaged DNA. Complete sequencing of the grapevine genome has revealed genes that are responsible for the synthesis of health-promoting compounds (resveratrol and other polyphenols). Another potential explanation for the observation that in some studies red wine does not appear to increase breast cancer risk, may be the fact that red wine is a nutritional aromatase inhibitor (AI). Aromatase inhibitors (AI) prevent the conversion of androgens to estrogens, thus a hormone-related mechanism might be involved.
In summary, the cancer risk should not be evaluated in isolation, one particular food factor (like wine consumption) should not be analysed out of context with its cultural and culinary habits. The effect of wine on cancer risk also depends on whether it is consumed with or without a meal and the nature of other foods consumed. There needs to be a distinction between different types of cancer and the influence of lifestyle (according to the World Cancer Research Fund, more than 1/3 of the cancers could be prevented by a healthy diet, regular physical activity and no weight gain) and genetic factors needs to be assessed.
In future studies, the focus should be more on the pattern of drinking, not just the average weekly amount of alcohol, and thus, have a better understanding of how moderate drinking impacts cancer risk. This will allow consumers to make better informed decisions about the risks and benefits of moderate wine consumption in the context of their overall health and at different stages of their life.
The above summary provide an overview of the topic, for more details and specific questions, please refer to the articles in the database.