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

Authors

  • G. BJELAKOVIC,

    1. The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshospitalet, Copenhagen, Denmark
    2. Department of Internal Medicine – Gastroenterology and Hepatology, Department of Anatomy, Medical Faculty, University of Nis, Nis, Serbia and Montenegro
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  • A. NAGORNI,

    1. Department of Internal Medicine – Gastroenterology and Hepatology, Department of Anatomy, Medical Faculty, University of Nis, Nis, Serbia and Montenegro
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  • D. NIKOLOVA,

    1. The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshospitalet, Copenhagen, Denmark
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  • R. G. SIMONETTI,

    1. The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshospitalet, Copenhagen, Denmark
    2. Divisione di Medicina, Ospedale V. Cervello, Palermo, Italy
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  • M. BJELAKOVIC,

    1. Department of Internal Medicine – Gastroenterology and Hepatology, Department of Anatomy, Medical Faculty, University of Nis, Nis, Serbia and Montenegro
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  • C. GLUUD

    1. The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshospitalet, Copenhagen, Denmark
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Dr G. Bjelakovic, Department of Internal Medicine – Gastroenterology and Hepatology, Medical Faculty, University of Nis, Bulevar Dr Zorana Djindjica 81, 18000 Nis, Serbia and Montenegro.
E-mail: goranb@junis.ni.ac.yu

Abstract

Summary

Background

Colorectal cancer may be prevented by reducing the development of adenomatous polyps.

Aim

To assess the benefits and harms of antioxidant supplements in preventing colorectal adenoma.

Methods

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.

Results

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 β-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).

Conclusion

We found no convincing evidence that antioxidant supplements have significant beneficial effect on primary or secondary prevention of colorectal adenoma.

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