Folate adenoma risk

B vitamin intake or vitamin blood concentrations have also been related to various cancers. The cancer types that have been best investigated with respeet to folic acid are colon cancer and colorectal cancer. Convincing evidence from observational studies led to the initiation of randomized controlled trials with folic acid in colorectal adenomas. However, similar to cardiovascular disease, there seems to be a discrepancy between the observational epidemiological studies that reported in the majority an inverse association of folate and cancer risk, and the effect of folic acid supplementation in the randomized controlled trials, which reported no effect of folic add on recurrence of colorectal adenoma risk. 

E. Giovannucci et al., Folate, Methionine, and Alcohol Intake and Risk of Colorectal Adenoma, J. Natl. Cancer Inst. 85 (1993) 875-84. 

By viewing the indicated food choices, and using tables of nutrients in foods, the researchers were able to estimate the daily intake of various nutrients, such as folate, vitamin C, calcium, and iron. The results for folate and vitamin C are shown separately for women and men in Table 11.2. The daily intakes for the nutrients were divided into four groups, as indicated. The risk for adenomas is expressed by a special term, called the odds ratio (OR) (see Appendix C). 

The association between folate intake and colorectal cancer in 27 observational epidemiological studies was analysed in a recent meta-analysis (Keimedy et al. 2011). This meta-analysis, which included 18 case-control studies and nine cohort studies, showed that high folate intake was associated with reduced risk of colorectal adenomas. The association was stronger in case-control studies [relative risk (RR) 0.85 95% confidence interval (Cl) 0.74-0.99] than in cohort studies (RR 0.92 95% Cl 0.81-1.05). 

While observational studies had reported inverse associations of dietary intake of folate (or blood levels of folate) with overall risks of cancer, colorectal cancer or breast cancer (Giovannucci et al. 2002 Larsson et al. 2007 Lin et al. 2008 Zhang et al. 2003), one small trial involving 1021 individuals with a prior history of colorectal adenoma suggested a possible adverse effect on both the risk of recurrent colorectal adenoma (Cole et al. 2007) and on prostate cancer... 

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