COLONIC MUCOSAL CONCENTRATIONS OF FOLATE CORRELATE WELL WITH BLOOD MEASUREMENTS OF FOLATE STATUS IN PERSONS WITH COLORECTAL POLYPS

Background: Estimates of habitual dietary folate intake are known to b e imprecisely correlated with systemic measures of folate status. Furt hermore, measurements of blood folate concentrations may not accuratel y reflect the concentration of folate in tissues of interest. This iss ue is important for assessing folate status in the colorectal mucosa b ecause low dietary intake or blood concentrations of folate are associ ated with an increased risk of colorectal neoplasia. Objective: We exa mined whether conventional measures of folate in blood and a more sens itive, inverse indicator of systemic folate status, serum homocysteine , accurately reflected folate concentrations in human colonic mucosa o btained by endoscopic biopsy. Design: In 30 persons with colorectal po lyps, blood samples were taken and biopsies of normal rectosigmoid muc osa performed at the time of colonoscopic polypectomy. Serum, red bloo d cell, and colonic mucosal folate and serum homocysteine concentratio ns were measured. Results: Serum and red blood cell folate and serum h omocysteine concentrations accurately reflected colonic mucosal folate concentrations; among these, serum homocysteine correlated best with mucosal concentrations. Folate concentrations in the normal rectosigmo id mucosa were significantly lower in persons with adenomatous polyps than in those with hyperplastic polyps (P = 0.04). Conventional measur es of systemic folate status were not significantly lower in those wit h adenomas, although serum homocysteine was mildly elevated (P = 0.04) . Conclusions: Our data underscore the ability of systemic measures of folate status, particularly serum homocysteine, to reflect folate con centrations in the colonic mucosa. Nevertheless, future studies that e xamine the ability of folate to modulate colorectal carcinogenesis may benefit from direct measurement of folate in the colon.