Fecal Biomarkers for Research on Dietary and Lifestyle Risk Factors in Colorectal Cancer Etiology

Stool, consisting of undigested food, endogenous secretions, and microbiota and exfoliated host cellular components, is an ideal biospecimen for non-invasive evaluation of the whole bowel environment regarding colorectal carcinogenesis and its biological effects on epithelial cells. Since the first suggestion, more than four decades ago, of stool volume as a potential risk marker for colorectal cancer, a variety of biomarkers, ranging from molecular to gross physical characteristics, have been measured in stool, fecal water or colorectal lavage. This article provides qualitative reviews of the association of these markers with established or postulated behavioral risk factors for colorectal cancer, i. e. diet, smoking, alcohol use, and physical activity. Published data based on fecal measurement are usually limited regarding both the number of publications and sample size within the studies, and associations have often been inferred frommeasurements of other specimen types, including blood, saliva, tissue and cell cultures. Studies concerning physical activity, smoking and alcohol are particularly sparse. Nevertheless, the studies suggest that dietary habits (high-fat-Western-style versus vegetarian and/or vegan) and red meat, calcium and/ or vitamin D, and dietary fiber intake may modulate several molecular pathways associated with colorectal cancer. Further development of fecal sample collection procedures suitable for a large number of subjects, and use of high-throughput and highdimensional assay techniques, are expected to facilitate epidemiological and prevention research elucidating the effects and biological mechanisms of these lifestyle factors regarding colorectal cancer risk.