Dietary intake of vitamins A, C, and E and the risk of colorectal adenoma
To comprehensively summarize the association between dietary intake of vitamins A, C, and E and the risk of colorectal adenoma (CRA), the precursor of colorectal cancer, relevant studies were identified in MEDLINE and EMBASE up to 31 October 2012. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were pooled with a random-effects model. Between-study heterogeneity was assessed using Cochran's Q and I statistics. A total of 13 studies with 3832 CRA cases were included in this meta-analysis. On the basis of the highest versus lowest analysis, dietary intake of vitamin C reduced the risk of CRA by 22% (SRRs 0.78, 95% CIs: 0.62-0.98). Subgroup analyses showed that this relation was not modified by BMI, smoking status, and dietary energy intake. Further, dietary intake of β-carotene was also inversely associated with the risk of CRA. However, dietary intake of vitamins A and E was not associated with the risk of CRA in overall and subgroup analyses (vitamin A: SRRs 0.87, 95% CIs: 0.67-1.14; vitamin E: SRRs 0.87, 95% CIs: 0.69-1.10). Our results indicate that dietary intake of vitamin C and β-carotene, but not vitamins A and E, could reduce the risk of CRA. However, these associations seem to be limited. Further investigation using large samples and a rigorous methodology is warranted.
[Show abstract] [Hide abstract] ABSTRACT: Carotenoid intake from natural sources has been hypothesized to reduce the risk of colorectal cancer (CRC). The aim of this study was to systematically review the epidemiological evidence for the association between carotenoid intake from natural sources and CRC development. We carried out a systematic review and meta-analysis of epidemiological studies to investigate whether the intake of specific carotenoids from natural sources, as well as combined carotenoids, is associated with the risk of CRC overall and by anatomic subsite. A comprehensive literature search of MEDLINE and Scopus databases was performed. Twenty-two articles were identified from the literature search, of which 16 were case-control studies and 6 were cohort studies. In the random-effects meta-analysis of case-control and cohort studies, we found no association between the intake of individual and total carotenoids and the risk of CRC overall and by anatomic subsite. Overall, our findings do not support a significant association between intake of specific carotenoids from dietary sources, as well as combined carotenoids, and the risk of CRC overall and by anatomic subsite. Copyright0Comments 0Citations
- "Studies carried out to assess the association between carotenoid intake from natural sources and CRC reported inconsistent findings (Slattery et al., 2000; Malila et al., 2002; Terry et al., 2002; Chiu et al., 2003; McCullough et al., 2003; Satia-Abouta et al., 2003; Murtaugh et al., 2004; Nkondjock and Ghadirian, 2004; Paiva et al., 2004; Ravasco et al., 2005; Kune and Watson, 2006; Levy et al., 2006; Shin et al., 2006; Wakai et al., 2007; Chaiter et al., 2009; Park et al., 2009; Roswall et al., 2010; Williams et al., 2010; Banque et al., 2012; Wang et al., 2012; Leenders et al., 2014; Lu et al., 2015). A recently published meta-analysis of observational studies (12 case–control studies and one nested case–control study) reported dietary intake of β-carotene to be associated inversely with the risk for development of colorectal adenomas (CRAs) (Xu et al., 2013). As CRAs are recognized to be a precursor lesion for CRC, it could be the case that β-carotene could prevent CRC occurrence by preventing the development of CRAs. "
[Show abstract] [Hide abstract] ABSTRACT: Whether dietary β-carotene and vitamin A intake protect against lung cancer risk is not clear. Therefore, we performed this meta-analysis to investigate the association between them. The related articles were searched using the databases PubMed and the Web of Knowledge up to May 2015. We used the random-effect model to estimate the relative risk (RR) and their 95% CI. Small-study effect was assessed using Egger's test. In total, 19 studies comprising 10,261 lung cancer cases met the inclusion criteria. The pooled RR and their 95% CI was 0.855 (0.739-0.989) for higher category of dietary vitamin A intake and lung cancer risk, especially among Asian populations and in the cohort studies. Evidence from 18 studies suggested that higher category of dietary β-carotene intake could reduce lung cancer risk (0.768 (0.675-0.874)).The associations were also significant in American and Asian populations. In conclusions, higher category of dietary β-carotene and vitamin A intakes could reduce the risk of lung cancer. However, the dose-response analysis was not performed due to the limited data in each individual study. Due to this limitation, further studies with detailed dose, cases and person-years for β-carotene and vitamin A of each category are wanted to assess this dose-response association.0Comments 0Citations
- "In addition to their anti-tumor effects it is possible that some carotenoids might exert procarcinogenic effects. Vitamin A and β-carotene had been reported associated with some cancers39404142. A recent study had reported that highest category of dietary vegetables and fruits intake could reduce lung cancer risk . "
[Show abstract] [Hide abstract] ABSTRACT: We attempted to systematically determine the association between dietary intake of vitamin C and risk of prostate cancer. PubMed and Embase were searched to obtain eligible studies published before February 2015. Cohort or case-control studies that reported the relative risk (RR)/odds ratio (OR) estimates with 95% confidence intervals (CIs) for the association between vitamin C intake and prostate cancer risk were included. Eighteen studies regarding dietary vitamin C intake were finally obtained, with a total of 103,658 subjects. The pooled RR of prostate cancer for the highest versus the lowest categories of dietary vitamin C intake was 0.89 (95%CI: 0.83-0.94; p = 0.000) with evidence of a moderate heterogeneity (I(2) = 39.4%, p = 0.045). Meta-regression analysis suggested that study design accounted for a major proportion of the heterogeneity. Stratifying the overall study according to study design yielded pooled RRs of 0.92 (95%CI: 0.86-0.99, p = 0.027) among cohort studies and 0.80 (95%CI: 0.71-0.89, p = 0.000) among case-control studies, with no heterogeneity in either subgroup. In the dose-response analysis, an inverse linear relationship between dietary vitamin C intake and prostate cancer risk was established, with a 150 mg/day dietary vitamin C intake conferred RRs of 0.91 (95%CI: 0.84-0.98, p = 0.018) in the overall studies, 0.95 (95%CI: 0.90-0.99, p = 0.039) in cohort studies, and 0.79 (95%CI: 0.69-0.91, p = 0.001) in case-control studies. In conclusion, intake of vitamin C from food was inversely associated with prostate cancer risk in this meta-analysis.0Comments 1Citation
- "Numerous epidemiological studies have explored the use of vitamin C in preventing the initiation of different cancers. Data from the previous meta-analyses have suggested that vitamin C intake is associated with reduced morbidity from breast cancer , and reduced risks of colorectal adenoma , lung cancer , and endometrial cancer . Many studies examining the association of vitamin C intake with prostate cancer risk have yielded inconsistent results. "