XIDATIVE STRESS IS IMPLIcated in most human diseases. 1,2 Antioxidants may decrease the oxidative damage and its alleged harmful effects. [3][4][5][6] Many people are taking antioxidant supplements, believing to improve their health and prevent diseases. [7][8][9][10] Whether antioxidant supplements are beneficial or harmful is uncertain. [11][12][13][14][15] Many primary or secondary prevention trials of antioxidant supplements have been conducted to prevent several diseases.We found that antioxidant supplements, with the potential exception of selenium, were without significant effects on gastrointestinal cancers and increased all-cause mortality. 14,15 We did not examine the effect of antioxidant supplements on all-cause mortality in all randomized prevention trials. 16 Our aim with the present systematic review was to analyze the effects of antioxidant supplements (beta carotene, vitamins A and E, vitamin C [ascorbic acid], and selenium) on all-cause mortality of adults included in primary and secondary prevention trials. METHODSThe present review follows the Cochrane Collaboration method 17 and is based on the principles of our peer-reviewed protocol and review on antioxidant supplements for gastrointestinal cancer prevention. 14,15,18,19 We included all primary and secondary prevention trials in adults randomized to receive beta caro-

Vitamin D3 seemed to decrease mortality in elderly people living independently or in institutional care. Vitamin D2, alfacalcidol and calcitriol had no statistically significant beneficial effects on mortality. Vitamin D3 combined with calcium increased nephrolithiasis. Both alfacalcidol and calcitriol increased hypercalcaemia. Because of risks of attrition bias originating from substantial dropout of participants and of outcome reporting bias due to a number of trials not reporting on mortality, as well as a number of other weaknesses in our evidence, further placebo-controlled randomised trials seem warranted.

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