Faecal phytic acid and its relation to other putative markers of risk for colorectal cancer

Abstract

Aims - Phytic acid, a major constituent of cereals, pulses, and seeds has been advocated as an important antioxidant component of dietary fibre that affords possible protection against colorectal cancer. This is supported by experimental studies showing it has antineoplastic activity in animal models of both colon and breast cancer. To date the concentration of faecal phytic acid in human clinical groups has not been evaluated. Therefore the faecal phytic acid content of adenoma patients drawn from a placebo controlled calcium intervention trial was evaluated. Methods - Phytic acid was measured in faecal extracts by an improved ion-pair high performance liquid chromatography method. Results - Phytic acid was detected in the range 0.68-4.00 μmol/g wet faeces and 55-2038 μmol/day. Linear regression analyses showed no association between stool phytic acid and lipid content. Strong correlations were seen, however, between phytic acid and iron content, both on a concentration (r = 0.52; p = 0.00004) and daily excretion (r = 0.76; p = 5.5 x 10-12) basis. Phytic acid was also strongly correlated with the daily excretion of calcium (r = 0.59; p = 1.36 x 10-6) and magnesium (r = 0.42; p = 0.001). Cell proliferation in the sigmoid colon, an intermediate biomarker of colorectal cancer was not significantly associated with faecal phytic acid, minerals or lipid content in this compromised clinical group. Conclusions - This improved method, developed for the determination of phytic acid in faeces should allow further studies on the role of phytic acid in the aetiology of colorectal cancer to be conducted on a population or case control basis.