Table 5.

Examples of some dietary components that decrease risk of CRC.

Fiber	(i) A high-fiber diet has a protective effect from CRC as it decreases transit time through the gastrointestinal tract, dilutes colonic contents, and enhances bacterial fermentation. This can increase the production of short-chain fatty acids that interfere with numerous regulators of the cell cycle, proliferation, and apoptosis such as β-catenin, p53, and caspase 3 genes [35, 36] (ii) Corn, beans, avocado, brown rice, lentils, pear, artichoke, carrots, oatmeal, broccoli, and apples are examples of diet rich in fiber [37]
Fish oil	(i) Fish oil rich in omega-3 fatty acids may inhibit the promotion and progression of cancer through suppression of arachidonic acid-derived eicosanoid biosynthesis, which results in altered immune response to cancer and modulation of inflammation, cell proliferation, apoptosis, metastasis, and angiogenesis [38] (ii) It also influences transcription factor activity, gene expression, and signal transduction, which leads to changes in metabolism, cell growth, and differentiation [38–40]
Olive oil	(i) Olive oil reduces deoxycholic acid in the human colon and rectum (ii) Deoxycholic acid was found to reduce diamine oxidase, a main enzyme for the metabolism of ingested histamine and control of mucosal proliferation in the ileal and the colonic mucosa [41]
Folate	(i) Folate acts as donors of methyl groups in the biosynthesis of nucleotide precursors used for DNA synthesis and methylation of DNA, RNA, and protein and participates in the maintenance of genomic stability [42, 43] (ii) Spinach, broccoli, strawberries, raspberries, beans, peas, lettuce, lentils, and celery are examples of diet rich in folate [37]
Calcium	(i) Calcium can suppress epithelial cell proliferation in the colon by binding to bile acids and ionized fatty acids [44] (ii) Calcium can act directly by reducing proliferation, stimulating differentiation, and inducing apoptosis via upregulation of p21 and Bcl-2 in the colonic mucosa [44–47]