Meta-analysis: Antioxidant supplements for primary and secondary prevention of colorectal adenoma

The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshospitalet, Copenhagen, Denmark.
Alimentary Pharmacology & Therapeutics (Impact Factor: 5.73). 07/2006; 24(2):281-91. DOI: 10.1111/j.1365-2036.2006.02970.x
Source: PubMed


Colorectal cancer may be prevented by reducing the development of adenomatous polyps.
To assess the benefits and harms of antioxidant supplements in preventing colorectal adenoma.
Using the Cochrane Collaboration methodology we reviewed all randomized clinical trials comparing antioxidant supplements with placebo or no intervention. We searched electronic databases and the reference lists until October 2005. Outcome measures were development of colorectal adenoma adverse events. We analysed dichotomous outcomes with fixed- and random-effects model meta-analyses and calculated the relative risk with 95% confidence interval.
We identified eight randomized trials (17 620 participants). Neither fixed-effect (relative risk: 0.93, 95% CI: 0.81-1.1) nor random-effect model meta-analyses (0.82, 0.60-1.1) showed statistically significant effects of supplementation with beta-carotene, vitamins A, C, E and selenium alone or in combination. Antioxidant supplements seemed to increase the development of colorectal adenoma in three low-bias risk trials (1.2, 0.99-1.4) and significantly decrease its development in five high-bias risk trials (0.59, 0.47-0.74). The estimates difference is significant (P < 0.0001). There was no significant difference between the intervention groups regarding adverse events, including mortality (0.82, 0.47-1.4).
We found no convincing evidence that antioxidant supplements have significant beneficial effect on primary or secondary prevention of colorectal adenoma.

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Available from: Christian Gluud, Sep 15, 2014
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    • "The results of another meta-analysis indicate that antioxidants do not seem to have a beneficial effect on preventing the recurrence of colorectal adenomas.55 "
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    • "[21], [22] Dietary supplement use and colorectal adenoma risk have been extensively investigated in the general population. No convincing evidence for an association between multivitamin supplement use, [23] folic acid supplement use, [24] and antioxidant supplement use and adenoma occurrence was found, [25], [26] whereas calcium supplement use might contribute to a lower risk of colorectal adenomas. [27] MMR gene mutation carriers might have a higher use of dietary supplements compared to the general Dutch population based on their health status and risk. "
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    ABSTRACT: Individuals with Lynch syndrome have a high lifetime risk of developing colorectal tumors. In this prospective cohort study of individuals with Lynch syndrome, we examined associations between use of dietary supplements and occurrence of colorectal adenomas. Using data of 470 individuals with Lynch syndrome in a prospective cohort study, associations between dietary supplement use and colorectal adenoma risk were evaluated by calculating hazard ratios (HR) and 95% confidence intervals (CI) using cox regression models adjusted for age, sex, and number of colonoscopies during person time. Robust sandwich covariance estimation was used to account for dependency within families. Of the 470 mismatch repair gene mutation carriers, 122 (26.0%) developed a colorectal adenoma during an overall median person time of 39.1 months. 40% of the study population used a dietary supplement. Use of any dietary supplement was not statistically significantly associated with colorectal adenoma risk (HR = 1.18; 95%CI 0.80-1.73). Multivitamin supplement use (HR = 1.15; 95%CI 0.72-1.84), vitamin C supplement use (HR = 1.57; 95%CI 0.93-2.63), calcium supplement use (HR = 0.69; 95%CI 0.25-1.92), and supplements containing fish oil (HR = 1.60; 95%CI 0.79-3.23) were also not associated with occurrence of colorectal adenomas. This prospective cohort study does not show inverse associations between dietary supplement use and occurrence of colorectal adenomas among individuals with Lynch syndrome. Further research is warranted to determine whether or not dietary supplement use is associated to colorectal adenoma and colorectal cancer risk in MMR gene mutation carriers.
    PLoS ONE 06/2013; 8(6):e66819. DOI:10.1371/journal.pone.0066819 · 3.23 Impact Factor
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    • "A high-quality meta-analysis of eight trials found that, compared with no treatment or placebo, there was no benefit of antioxidants (beta-carotene, vitamin A, vitamin C, vitamin E, or selenium) in decreasing the risk of CRC. Vitamin E was, in fact, found to increase the risk of colorectal adenomas [28]. "
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    09/2010; 1(3):513-21. DOI:10.1007/s13167-010-0047-9
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