British Journal of Nutrition

Full Papers

Polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, intakes of folate and related B vitamins and colorectal cancer: a case–control study in a population with relatively low folate intake

Linda Sharpa1a2 c1, Julian Littlea1a3, Nigel T. Brocktona1a4, Seonaidh C. Cottona1a5, Lindsey F. Massona1a5, Neva E. Haitesa1 and Jim Cassidya1a6

a1 Department of Medicine and Therapeutics, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK

a2 National Cancer Registry Ireland, Elm Court, Boreenmanna Road, Cork, Republic of Ireland

a3 Canada Research Chair in Human Genome Epidemiology, Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Canada

a4 Maternal and Child Health Sciences, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK

a5 Department of Public Health, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK

a6 Beatson Oncology Centre, Western Infirmary, Glasgow G11 6NT, UK

Abstract

Folate is key in one-carbon metabolism, disruption of which can interfere with DNA synthesis, repair, and methylation. Efficient one-carbon metabolism requires other B vitamins and the optimal activity of enzymes including 5,10-methylenetetrahydrofolate reductase (MTHFR). We report a population-based case–control study of folate intake, related dietary factors and MTHFR polymorphisms (C677T, A1298C) and colorectal cancer in a population with relatively high colorectal cancer incidence and relatively low folate intake. A total of 264 cases with histologically confirmed incident colorectal cancer and 408 controls participated. There was no clear trend in risk with reported intakes of total, or dietary, folate, riboflavin, vitamin B12 or vitamin B6, nor were there interactions between folate intake and the other B vitamins or alcohol. For C677T, risk decreased with increasing variant alleles (multivariate OR for CT v. CC = 0·77 (95 % CI 0·52, 1·16); OR for TT v. CC = 0·62 (95 % CI 0·31, 1·24)), which, although not statistically significant, was consistent with previous studies. For A1298C, compared with AA subjects, CC subjects had modest, non-significant, reduced risk (multivariate OR = 0·81 (95 % CI 0·45, 1·49)). There were significant interactions between total folate and C677T (P = 0·029) and A1298C (P = 0·025), and total vitamin B6 and both polymorphisms (C677T, P = 0·016; A1298C, P = 0·033), although the patterns observed differed from previous studies. Seen against the setting of low folate intake, the results suggest that the role of folate metabolism in colorectal cancer aetiology may be more complex than previously thought. Investigation of particular folate vitamers (for example, tetrahydrofolate, 5,10-methylenetetrahydrofolate) may help clarify carcinogenesis pathways.

(Received October 16 2006)

(Revised May 21 2007)

(Accepted June 15 2007)

Correspondence:

c1 Corresponding author: Dr Linda Sharp, fax +353 21 4318016, email linda.sharp@ncri.ie

Footnotes

Abbreviations: MTHFR, 5,10-methylenetetrahydrofolate reductase

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