Prepared by Professor R Curtis Ellison Epidemiologist, Institute on Lifestyle & Health Boston University Introduction
During 2009, more than 200 new publications/policy statements have been reviewed. Comments on some of what are considered to be important topics covered by scientific papers during the past yea are summarized below.
Effects of alcohol consumption on risk of cancer
In a study based on about one million women, Allen et al reported on a total of 68,775 cases of cancer, including 28,380 breast cancers, 5,203 lung cancers, and 4,169 colon cancers. Little difference in effect was noted between consumption of wine and consumption of other beverages containing alcohol. The key findings of the study support a positive relation between increasing alcohol consumption and upper aerodigestive cancers (mouth, pharynx, esophagus, etc.), but only if the drinker is also a smoker. Lesser increases in risk with alcohol consumption were noted for cancers of the rectum and breast. Increasing alcohol intake was associated with lower risks of thyroid cancer, renal cell cancer, and non-Hodgkins lymphoma. These findings generally support what has been shown in previous epidemiologic studies. It was not possible from the data presented to determine a lower threshold of effect of alcohol on the different cancers, or to judge the net effects on health (taking into consideration not just cancer but effects of alcohol intake on cardiovascular disease, dementia, total mortality, etc.).
An interesting editorial by El Serag and Lagergren was published that described three new papers that raise questions about the formerly held general view that alcohol increases the risk of GERD (gastroesophageal reflux disease) and its serious outcomes, Barrett's esophagus (BE) and adenocarcinoma of the esophagus (EAC). All three studies suggested a decrease in risk of disease for consumers of wine. The authors are appropriately cautious in their conclusions: "Although these interesting findings are suggestive of a protective effect of modest intake of wine with regard to the risk of developing BE or EAC, there are several biases, some of which are practically impossible to control, that make it important to maintain a healthy skepticism of these findings. Possibly, more definitive data will become available from cohort studies and experimental data."
A well-done analysis of an observational study published by Duffy et al was based on the very large number of women in the WHI (Women's Health Initiative). Unlike findings in many previous observational studies, the findings from this analysis provide no support for the theory that adequate folate intake negates an increase in breast cancer risk among women consuming alcohol. The authors point out that the recruitment of women into this study occurred after there had been an increase in the folate intake of the US population from the fortification of cereals and grains, and this could have resulted in fewer women with inadequate folate intake. Further, their follow-up time (5.5 years) may not have been adequate for any protective effect of folate to be seen. In this study, alcohol intake was associated with a slight increase in breast cancer risk, but intake of folate (from diet and/or supplements) had no effect on the association. Thus, unlike several other large studies, this study does not support a protective effect against breast cancer from high folate intake among women drinking alcohol. While this study showed no reduction in risk of breast cancer from folate, a new clinical trial among patients with coronary disease (Mager A, et al. Impact of homocysteinelowering vitamin therapy on long-term outcome of patients with coronary artery disease. Am J Cardiol 2009;104:745-749) showed that 400 ug/day of folic acid markedly lowered mortality among subjects with elevated levels of homocysteine. Hence, perhaps we should not give up on folate yet.
A paper by Knight et al compared alcohol intake between 708 women who developed a second, contralateral, breast cancer after an initial breast cancer and 1,399 with an initial breast cancer but no subsequent contralateral tumor. They reported that women who stated that they had ever been a regular drinker had a 30% higher risk of the second tumor. The odds ratio for alcohol consumption between the first and second breast cancers was slightly less (OR = 1.2 , 95% CI of 0.9, 1.5). Only 10% of women changed their drinking habits after the initial cancer. No data are given regarding the association of alcohol intake with the original tumor. Despite some analytic problems, this study tends to support the conclusions of the authors: regular drinking is associated with a slight increase in the risk of a second breast cancer in the contralateral breast among women who have had an initial breast cancer. Smoking was not associated with a second breast cancer.