Does alcohol cause breast cancer?
We talk to our Chief Medical Adviser, Professor Paul Wallace to find out the facts about alcohol and breast cancer.
When asked to name the main health effects of drinking too much alcohol, many people will first say liver disease. Others will mention heart disease. Some will name mental health issues. Cancers are often low down on the public’s alcohol effects list.
But they shouldn’t be – especially breast cancer.
It is clear from a number of large scale studies that there is a link between alcohol consumption and cancer. One in five (21.6%) of all alcohol-related deaths are due to cancer. (1) And breast cancer is the most common cancer among women (2) and second only to lung cancer as a cause of cancer death in women. (3)
Professor Paul Wallace, Drinkaware’s Chief Medical Adviser, believes that more people should know that alcohol can increase women’s risk of getting breast cancer.
“My impression is that my patients don’t know about the link between alcohol and breast cancer any more than they do about the association between alcohol and fertility. We can do more to increase awareness.”
We spoke to Professor Wallace to get the facts about alcohol and breast cancer and learnt that:
- There is a lot of evidence to suggest that alcohol increases the risk of developing breast cancer.
- Drinking alcohol does not mean you will get breast cancer, it means your risk of developing it will be increased.
- How much you drink over your lifetime is what increases the risk.
Although alcohol does increase the risk, taken with all the other factors, its contribution to overall causation of breast cancer is estimated to be only about 4%. The advice is that if you do regularly drink it should be within the government's daily unit guidelines. The government advises that women should not regularly drink more than the daily unit guidelines of 2-3 units of alcohol (equivalent to a 175 ml glass of wine). ‘Regularly’ means drinking every day or most days of the week.
Evidence which shows that alcohol increases the risk of developing breast cancer is not new. Professor Wallace confirms that we have known for years that your risk of developing breast cancer increases when you drink. Overall, women have a 9.5% chance of getting breast cancer before they are 75. One study found that drinking every day – even a small amount – raises that risk to 10.6%. (4) Professor Wallace says, though, that the overall risk (anything that affects your chance of getting a disease) is based on how much you drink on average each day over a lifetime.
Professor Wallace says a very important large scale recent study which has again demonstrated the link between alcohol and breast cancer is the Million Women Study. Run by Oxford University, it is ongoing and involves 1.3 million women across the UK (5). “It shows that the relative risk [the chance of one group developing breast cancer, compared to another] of breast cancer increases by 6% for each 10 grams of alcohol you drink, slightly over a unit of alcohol a day. This study indicated that the effect of alcohol appears to be independent of whether you smoke or not. It suggested that smoking did not on its own increase the risk of breast cancer.
How alcohol increases the risk
The exact ways alcohol increases the risk of developing breast cancer are not fully understood but we do know some of the potential mechanisms. Professor Wallace says that the increased risk is almost certainly in part because alcohol breaks down into a substance called acetaldehyde, which can cause genetic mutations – a permanent change in the DNA sequence that makes up genes. This can trigger a response from the body leading to the development of cancerous cells.
Alcohol is also thought to increase the production of the female hormone oestrogen in pre-menopausal and post-menopausal women. One characteristic of a cancer cell is that it multiplies out of control and in certain types of breast cancer, high circulating levels of oestrogen can make this more likely to happen. Alcohol can also alter the immune system and contribute to nutritional deficiencies, including folic acid (which women need in the early stages of pregnancy), vitamins A, B6, D and E and zinc, all of which may make it more difficult for the body to fight cancerous cells.
Assessing the risk
Professor Wallace says it’s important to put this risk into context. There are many other factors which increase the risk of developing breast cancer. “I often sit down with my patients and explain that there certain factors we can do nothing about,” he says. “For example, the fact that you are female is a risk factor in developing breast cancer. We also know breast cancer is age-related and that you’re more prone to breast cancer if it is part of your family history. These are all factors beyond our control.
“We also know that risk is related to the ‘hormone environment’ that women experience during the course of their mature years: for example, early pregnancy, child birth and breastfeeding all exert a protective effect. Seen in relation to all of these other factors, excessive alcohol consumption appears to contribute about 4% of the overall risk of breast cancer in developed countries.”
The advice, then, if you are a female drinker, is not to panic but to drink sensibly: the more you cut down on alcohol the more you reduce your risk.
“Drink within the daily unit guidelines. When taken overall, looking at all the things alcohol does, the risk at these levels is minimal. Life isn’t about zero risk. Even if you lived in a bubble and didn’t ever go outside, you would still be likely to get osteoporosis because you didn’t exercise!”.
Male breast cancer
If you’re a male drinker worried about developing breast cancer, the advice to not regularly drink more than the government's daily unit guidelines – 3-4 units for men (equivalent to a pint and a half of 4% beer) is the same. But male breast cancer is far rarer and more research is needed to understand the link between alcohol and the increased risk of developing it. Professor Wallace says there are other effects of drinking that male drinkers should be concerned about first.
One thing we can all do to decrease the risk of developing breast cancer is exercise and eat well. University of California research (6) has shown that eating at least five servings of vegetables and fruits a day and walking briskly for 30 minutes, six days a week, decreases women’s chances of getting breast cancer by half. “Regular exercise appears to have remarkable protective effects on both physical and psychological health” confirms Professor Wallace.
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(1) Global status report on alcohol and health, World Health Organization 2011. Available at:http://www.who.int/substance_abuse/publications/global_alcohol_report/en/
(2) Cancer Research Uk - 'Cancer incidence for common cancers'. Available at:http://info.cancerresearchuk.org/cancerstats/incidence/commoncancers/uk-cancer-incidence-statistics-for-common-cancers
(3) Cancer Research UK - 'Cancer mortality for common cancers'. Available at:http://info.cancerresearchuk.org/cancerstats/mortality/cancerdeaths/uk-cancer-mortality-statistics-for-common-cancers
(4) Allen et al, “Moderate alcohol intake and cancer incidence in women”, Journal of the National Cancer Institute, Vol. 101, No. 5, pp. 296-305, 2009. Available at:http://jnci.oxfordjournals.org/content/101/5/296.short
(5) The Million Women Study. Available at:http://www.millionwomenstudy.org
6) Pierce, John and Rock, Cheryl, “Women's Health Eating and Living (WHEL) study”, San Diego's (UCSD) Moores Cancer Centre, University of California, 2007. Available at:http://www.healthyeatingucsd.org/pages/whelStudy.htm
Page updated: May 2013
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