Scientists in Denmark published the results of a study in the British Medical Journal on April 12th, 2016, which found that postmenopausal women who consistently drink more than 14 drinks a week over a five-year period, have a higher risk of developing breast cancer and a lower risk of coronary heart disease when compared with women with normal alcohol consumption habits.
The scientific interest in the subject is widespread due to the opposite risk associations of coronary heart disease and breast cancer with increased alcohol consumption. Both of these diseases are present at very high prevalence and incidence rates worldwide.
Coronary heart disease is the number one cause for fatalities in the US. Every one in four women dies due to heart disease, of which 64% women die suddenly without any previous symptoms. Moreover, breast cancer is the most prevalent cancer in the US with 1 in 8 women developing the diseases in their lifetimes.
Previous studies have mostly focused on disease trends in the short term. However, this study had a more focused, long-term and randomized study design, which increased the scientific accuracy of the results.
Data from the Diet, Cancer, and Health Study was included in the research. The study followed a group of women who were born in Denmark, had no history of any kind of cancer, and were living in the greater Copenhagen or Aarhus area. The participants were again examined, where 81% of the women from the same group from 1999-2003 agreed to a second round of the study. The mean follow-up time of observing participants was nearly 11 years. The study took place between the years of 1993 and 1998.
With nearly 22,000 post-menopause females involved and more than 2,000 deaths, it was found that 1,054 women developed breast cancer and 1,750 had coronary heart disease. The mean age of the participants was 62 years and 32% had stable alcohol intake.
Women with increased alcohol intake had a higher risk of developing breast cancer with a hazard ratio of 1.38. Excluding women with history of benign breast cancer presented the same results — women who had increased consumption of alcohol compared to the ones who had stable intake had lower risks of coronary heart disease with a hazard ratio of 0.88.
The research was conducted at multiple centers which included National Institute of Public Health (NIPH), University of Southern Denmark, University of Copenhagen, Danish Cancer Society Research Centre (DCRC) in Copenhagen, Aarhus University, and Aalborg University Hospital. The researchers did not disclose if they any received funding for the study.
Alcohol intake has previously been linked with decreased risk of coronary heart disease and increased risk of breast cancer though at the time little was known about the mechanism of action for these associations. These trends were often explained by scientists in the form of hypothesis as no established scientific research had properly described the causalty mechanism for the phenomenon.
Increase in the risk of breast cancer is often explained by two major hypotheses. First, circulating estrogen levels can be altered by increased alcohol consumption which can lead to cancer. Secondly, alcohol can be converted into a compound named acetaldehyde by alcohol dehydrogenase (ADH). Furthermore, the incidence of acetaldehyde, a genotoxic chemical, has been linked with increased risk of breast cancer through a variety of mechanisms, most popular being the damaging of DNA.
Decreased risk of coronary heart disease is often explained by alcohol-affected levels of high density lipoprotein cholesterol, inhibited platelet activation, and reduced levels of fibrinogen.
Previously carriers of the A allele of ADH1B (rs1229984), associated with non-drinking and lower alcohol consumption, have shown lower odds of developing coronary heart disease.
Epidemiologists at the Mediterranean Neurological Institute (INM) in Italy only this week published a study in Nutrition, Metabolism & Cardiovascular Disease (NMCD), in which analysis of more than one 150 studies came to the same conclusion and suggested that men drinking up to 1.4 pints of beer and women consuming half that amount, can have a beneficial effect on health of their heart.
In the US, the Centers for Disease Control and Prevention (CDC) recommends no more than two drinks per day for men and one drink per day for women. A standard drink consists of 8 ounces of malt liquor, 12 ounces of beer, 5 ounces of wine, and 1.5 ounces of distilled liquor. The guidelines do not suggest that non-drinkers should take up drinking in any way. Additionally, the National Institutes of Health (NIH) England also recommends the same amount of drinks for adults.
However, Dame Sally, Chief Medical Officer for NIH, was unimpressed with these results and spoke to the House of Commons, suggesting that the findings were not robust enough.
Professor Tim Key, Deputy Director, Cancer Epidemiology Unit at the University of Oxford, agreed with her assessment. According to Professor Key, “Risk of heart disease can be reduced substantially by other lifestyle changes, as well as by drugs such as statins shown to be effective in primary prevention.”
In January, prior to addressing the house, Dame Sally issued new alcohol consumption guidelines which suggested safety levels of alcohol at 14 units per week, meaning less than two drinks of wine a day.
She urged women to consider the consequences before consuming wine at more than the recommended limits as 11% of diagnosed women in England have breast cancer directly associated with alcohol consumption.