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Findings about alcohol use in young women should be taken in context

September 9, 2013

By Andy Koopmans

Dr. Christopher Li

Dr. Christopher Li is an epidemiologist and breast cancer researcher in the Public Health Sciences Division at Fred Hutch.

A recent study published in the Journal of the National Cancer Institute provides evidence that alcohol consumption prior to first pregnancy is associated with an increased risk of breast cancer and proliferative benign breast disease, which is a group of noncancerous conditions that may increase the risk of developing breast cancer.

The study, conducted by Drs. Ying Liu and Graham Colditz and colleagues at Washington University School of Medicine, found that 4 percent of breast cancer cases and 11 percent of proliferative benign breast disease cases could be attributed to drinking before first pregnancy, with the relative risk being more pronounced in women whose time between first menstruation and first pregnancy was 10 years or longer.

However, Dr. Christopher Li, an epidemiologist and breast cancer researcher in the Public Health Sciences Division at Fred Hutchinson Cancer Research Center, said that while alcohol consumption is known to be the most consistently observed dietary factor related to breast cancer, the increase in risk observed in this study was quite modest.

“The increase cited in this study is among women who drank 10 grams of alcohol per day, which is equivalent to about one drink per day. The observed 11 percent increased risk of breast cancer among women who consumed this amount prior to their first pregnancy is essentially the same as the risk of breast cancer that has been observed across multiple studies comparing women who drink alcohol compared to non-drinkers. Compared to the relationship between smoking and lung cancer, for example, where current smokers have a greater than 200 percent increased risk of lung cancer, alcohol is a relatively weak risk factor for breast cancer and the proportion of breast cancers attributable to alcohol is quite small. And this is only for women consuming one drink per day. The risk is even lower for those who consume less than that.” he said.

The researchers studied participant data from the Nurses’ Health Study II, tracking registered nurses between the ages of 25 and 42 from several states who answered questions about a variety of diseases and health-related topics including alcohol use, smoking, hormone use, pregnancy history and menopausal status. The study tracked breast cancer incidence among 91,000 women with no cancer history and who had given birth and who were tracked for 20 years. The incidence of proliferative benign breast disease was also tracked among a subset of more than 60,000 women who were followed for 10 years. Li said that the Liu-Colditz study is consistent with what is known about the biological mechanism linking alcohol use and breast cancer: Alcohol consumption has been shown through feeding studies to increase estrogen, which in turn is a factor that is associated with an increased risk of breast cancer. However, he said that the study did not distinguish the type of alcohol consumption, noting that consumption of antioxidant-rich red wine, for example, has been shown to have health benefits that might mitigate breast cancer risk at the level of consumption cited.

“Unfortunately there aren’t a lot of things young women can do to lower their risk for breast cancer since most of the things that increase risk are not easily modifiable, such as family history or pregnancy history,” he said.  “Alcohol is one of the potentially modifiable risk factors for breast cancer, but even if large numbers of women were to stop consuming alcohol the potential impact of this on reducing breast cancer incidence rates would likely be quite small.”

2 Comments leave one →
  1. September 9, 2013 9:55 am

    Great post. I found this study a very…peculiar one. Not only, as you have identified here, is it that the percentage risk increase is not particularly significant but the reason behind alcohol consumption and cancer risk had already been established as a link with hormone levels. I found it even stranger when you look at the mechanism of gathering information; am I correct in thinking participants were asked to keep tabs (no pun intended) on their alcohol consumption? I see the relevance of the study but the way that the media has portrayed it is as if it’s a definitive link. I suppose I shouldn’t be too surprised by that though.

    • September 13, 2013 9:05 am

      Thanks for your comment. According to the study, the women in the cohort were asked in 1989 about their alcohol consumption in four age periods: ages 15-17, 18-22, 23-30 and 31-40. They were asked about the total number of drinks of alcohol (including beer, wine and liquor together) consumed at different ages. Alcohol consumption for the previous year was asked separately for beer, for wine, and for liquor in nine categories ranging from “none or <1 month" to "40+/week." Current drinking was updated in 1991, 1995, 1999 and 2003.

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