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Critique 165: Fibre intake may modify the association of alcohol consumption with certain hormone-dependent cancers

The positive association between alcohol intake and certain hormone-dependent cancers (especially breast cancer) noted in many studies has been attributed to an effect of alcohol through an increase in levels of estrogen and other hormones. The present study had extensive dietary data on more than 5,000 men and women in France, among whom comparisons were made between the sex-specific tertile of alcohol intake and the risk of hormone-related cancers (breast, prostate, ovarian, endometrial, and testicular).

The study found that, overall, the risk of some cancers (e.g., breast) but not others (e.g., prostate) were positively related to reported alcohol intake. The key results reported by the authors are that when the risks of cancer were related to alcohol while adjusting for fibre intake, subjects whose fibre intake was below the median value showed higher risks of cancer related to alcohol, but not subjects with higher fibre intake. For example, when the risk of breast cancer in women was related to the tertile of their alcohol intake, the 2nd tertile showed a HR of 1.55 (1.01 – 2.38) and the 3rd tertile (HR 1.70, CI 1.11 – 2.61), when compared with women in the lowest tertile.

For prostate cancer in men, however, the 2nd tertile showed a HR of 1.28 (CI 0.82 – 2.00) and the 3rd tertile a HR of 0.89 (CI 0.55 – 1.45). The interaction terms between alcohol intake and cancer were not significant for all hormone-dependent cancers or for breast cancer. Only the interaction term for prostate cancer reached statistical significance, but here the relationship between tertile of alcohol intake even among subjects with low dietary fibre did not show a clear dose-response relation.

Forum members had concerns about the large number of potential confounders in these analyses (e.g., different effects for different types of fibre, the intake of fibre being just a marker for folate intake or for other dietary or lifestyle factors), that made it difficult for the authors to reach firm conclusions. Unfortunately, the numbers of tumors for each of the sub-groups were often too small to give meaningful results. And there was no data on alcohol drinking pattern (regular moderate versus binge drinking) or type of beverage consumed. Thus, while this study indicates that alcohol intake may relate to certain hormone-dependent cancers, the analyses do not present a clear demonstration as to whether it is fibre intake or some other related factor that may modify the association.

Reference: Chhim A-S, Fassier P, Latino-Martel P, Druesne-Pecollo N, Zelek L, Duverger L, Hercberg S, Galan P, Deschasaux M, Touvier M. Prospective association between alcohol intake and hormone dependent cancer risk: modulation by dietary fibre intake. Amer J Clin Nutr 2015; pre-publication. Doi: 10.3945/ajcn.114.098418.

For the full critique of these papers, and general comments on alcohol and cancer, by members of the International Scientific Forum on Alcohol Research, please click here.
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