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Al Pater posted study  to the CR email list (thanks Al), that was a meta-analysis of studies of the relationship between vitamin intake and stomach (gastric) cancer risk. It found that several vitamins, including Vitamin A, C and E, in modest doses, could indeed reduce the risk of stomach cancer by about 25%. But high doses of those same vitamins resulted in an increased risk of almost the same magnitude. They also observed that modest doses of these vitamins were only beneficial for gastric cancer when they came from food (plants or animals) - vitamin supplements showed no such benefits. The authors speculate that the reason could be differences in bioavailability of vitamins from foods vs. pills: The current study also draws attention to the fact that vitamins from food (plant or animal) contribute more to reductions in GC risk than synthetic vitamin supplements. Some investigators have noted that the bioavailability of vitamins differs depending on whether the vitamin comes from food or is synthetic, which could explain the results. For example, Carr reported differences in bioavailability between synthetic and kiwifruit-derived vitamin C in a randomized crossover pharmacokinetic study [ref]. But it seems at least as plausible to me that the benefits come not just from these specific vitamins (heck, in the case of vitamin E alone there is really a whole family of vitamins rather than just a single vitamin E), but from the many beneficial phytochemicals in foods, for which these three vitamins are merely markers. --Dean ---------  Vitamin intake reduce the risk of gastric cancer: meta-analysis and systematic review of randomized and observational studies. Kong P, Cai Q, Geng Q, Wang J, Lan Y, Zhan Y, Xu D. PLoS One. 2014 Dec 30;9(12):e116060. doi: 10.1371/journal.pone.0116060. eCollection 2014. Review. PMID: 25549091 Free PMC Article http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4280145/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4280145/pdf/pone.0116060.pdf Abstract AIM: The association between vitamin intake and gastric cancer (GC) has been widely debated due to the relatively weak evidence. In this study, a meta-analysis of prospective and well designed observational studies were performed to explore this association. METHODS: MEDLINE, Cochrane Library, and Sciencedirect were searched for studies of vitamin consumption and gastric cancer. This produced 47 relevant studies covering 1,221,392 human subjects. Random effects models were used to estimate summary relative risk (RR). Dose-response, subgroup, sensitivity, meta-regression, and publication bias analyses were conducted. RESULTS: The RR of gastric cancer in the group with the highest vitamin intake was compared to that of the lowest intake group. Total vitamin intake was 0.78 (95% CI, 0.71-0.83). In 9 studies that individuals were given doses at least 4 times above the tolerable upper intake (UL) vitamins, the RR was 1.20 (95% CI, 0.99-1.44). However, in 17 studies that individuals received doses below the UL, the RR was 0.76 (95% CI, 0.68-0.86). Dose-response analysis was conducted on different increments in different types of vitamins (vitamin A: 1.5 mg/day, vitamin C: 100 mg/day, vitamin E: 10 mg/day) intake with a significant reduction in the risk of gastric cancer, respectively, 29% in vitamin A, 26% in vitamin C, and 24% in vitamin E. CONCLUSION: This meta-analysis clearly demonstrated that low doses of vitamins can significantly reduce the risk of GC, especially vitamin A, vitamin C, vitamin E. Table 2. Subgroup analyses of vitamins intake and gastric cancer Risk. Heterogeneity test ------------------------------------ Group NO. of reports RR (95%) Chi^2 P(I^2) ------------------------------------\ Vitamin source plant 15 0.79(0.69,0.89) 36.96 0.002 65 animal 11 0.78(0.68,0.89) 25.93 0.0003 61 drug supplement 16 0.95(0.80,1.13) 33.09 0.58 55