SCFAs have been shown to decrease
colonic pH and inhibit carcinogenesis (73). Colorectal adenomas are the precursors of most colorectal cancers. The effect of diet in relation to colorectal adenomas and adenoma recurrence was explored in several studies. Diets high in wheat bran (74), fruit and vegetables (49,75), citrus fruits (19), cruciferous vegetables (76), dark-green vegetables and onions garlic (77) and tomatoes (23) may confer protection against colorectal adenomas Inhibitors,research,lifescience,medical and subsequently colorectal carcinoma. Some prospective studies did not show this association (74,75). Early meta-analyses of case-control studies have generally shown a protective association between fibre and colorectal cancer (78,79). In one study, high fibre diet was associated with decreased survival (80). Cohort studies yielded mixed results often showing none or a weak inverse association between dietary fiber and risk of colorectal cancer (19,28,37,38). Data from the European Prospective Investigation Inhibitors,research,lifescience,medical into Cancer and Nutrition (EPIC) cohort, the Prostate, Lung, Colorectal, and Ovarian (PLCO) Inhibitors,research,lifescience,medical Cancer Screening Trial and the Swedish mammography cohort study showed reduced risk of colorectal cancer and colorectal adenomas among people who consumed the highest amounts of fibre particularly from grains fruits and vegetable (81-85). However, in a meta-analysis of
prospective studies, Park et al. suggested Inhibitors,research,lifescience,medical that high dietary fiber intake was actually not associated with a reduced risk of colorectal cancer (86). In a VX-689 clinical trial recent meta-analysis of prospective cohort and nested case-control studies of dietary fibre the authors suggest a 10% reduction in risk of colorectal Inhibitors,research,lifescience,medical cancer for each 10 g/day intake of
total dietary fibre and cereal fibre (87). Whole grain was also associated inversely (87). Other studies, did not suggest a protective association with specific subtypes of fibre such as fruit, vegetable or cereal (27,88,89). One can conclude that the evidence for fibre is unclear in terms of benefit in reducing colonic adenoma pathway and colorectal cancer formation. There are discrepancices between case-control and prospective cohort studies for reasons such as recall bias, selection bias and sample size. The general health benefits of below fibre which may pertain to a variety of cancers as well as the other benefits to the colon such as diverticulosis and constipation suggests that a high fibre diet including wheat bran, cereal, whole grain, citrus fruits, cruciferous vegetables, dark-green vegetables, onions, garlic and tomatoes may be recommended. Folic acid/folate (vitamin B9) These are water-soluble vitamins found in fruits, dark green vegetables and dried beans. Humans are not able to synthesize this vitamin, which has to come from dietary sources.