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Responses of Biomarkers of Folate and Riboflavin Status to Folate and Riboflavin Supplementation in Healthy and Colorectal Polyp Patients (The FAB2 Study)

¹ Human Nutrition Unit, University of Sheffield, Sheffield, United Kingdom; ² Human Nutrition Research Centre, Newcastle University, Newcastle, United Kingdom; ³ North Tyneside General Hospital, Rake Lane, North Shields, United Kingdom; and ⁴ School of Agriculture, Food Science and Veterinary Medicine, University College, Dublin, Ireland

Requests for reprints: Hilary J. Powers, Human Nutrition Unit, Section of Oncology, University of Sheffield, School of Medicine, Beech Hill Road, Sheffield S10 2RX. Phone: 44-4226-1346. E-mail: h.j.powers{at}sheffield.ac.uk

Epidemiologic data suggest that increasing folate intake may protect against colorectal cancer. Riboflavin may interact with folate to modulate the effect. A double-blind randomized placebo-controlled intervention study (the FAB2 Study) was carried out in healthy controls and patients with colorectal polyps (adenomatous and hyperplastic) to examine effects of folic acid and riboflavin supplements on biomarkers of nutrient status and on putative biomarkers of colorectal cancer risk (DNA methylation and DNA damage; to be reported elsewhere). Ninety-eight healthy controls and 106 patients with colorectal polyps were stratified for the thermolabile variant of methylene tetrahydrofolate reductase, MTHFR C677T, and were randomized to receive 400 µg of folic acid, 1,200 µg of folic acid, or 400 µg of folic acid plus 5 mg of riboflavin or placebo for 6 to 8 weeks. Blood samples and colon biopsy samples were collected for the measurement of biomarkers of folate and riboflavin status. Supplementation with folic acid elicited a significant increase in mucosal 5-methyl tetrahydrofolate, and a marked increase in RBC and plasma, with a dose-response. Measures of riboflavin status improved in response to riboflavin supplementation. Riboflavin supplement enhanced the response to low-dose folate in people carrying at least one T allele and having polyps. The magnitude of the response in mucosal folate was positively related to the increase in plasma 5-methyl tetrahydrofolate but was not different between the healthy group and polyp patients. Colorectal mucosal folate concentration responds to folic acid supplementation to an extent comparable to that seen in plasma, but with a suggestion of an upper limit. (Cancer Epidemiol Biomarkers Prev 2007;16(10):2128–35)