Category: Clinical

Month: 16 Sep 2017

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Systematic review of antioxidant vitamin and mineral use in preventing AMD suggests no benefit when analysed in >76,000 people

A systematic review and meta-analysis to determine whether or not taking antioxidant vitamin or mineral supplements, or both, prevent the development of AMD has found no evidence of benefit to their use. The study, conducted by researchers from the London School of Hygiene & Tropical Medicine and the City University of London, published their findings in the Cochrane Database of Systematic Reviews (2017, Jul 30:7). In a second study to assess the effects of antioxidant vitamin or mineral supplementation on the progression of AMD in people with the disease, the authors concluded that antioxidant and mineral supplementation may provide some delay in progression of the disorder in a single study but commented that the findings may not be generalizable to other populations.

 

In the study to assess preventive use of antioxidant vitamin or mineral supplements, the authors analysed five randomised controlled trials comprising data from 76,576 participants. The trials analysed had been conducted in the USA, Australia and Finland and had investigated the use of vitamin C, vitamin E, beta carotene and mutlivitamin supplements. The average treatment and follow-up duration of the studies ranged from 4 to 10 years. Evidence gathered from the analysis showed that vitamin E supplements did not prevent the development of any AMD, risk ratio (RR) 0.97, 95% confidence interval (CI) 0.90 to 1.06; but instead may slightly increase the risk of late AMD, risk ratio 1.22, 95% CI 0.89 to 1.67, compared with placebo. Interestingly, two studies reported a similar number of adverse events in both the vitamin E and placebo groups, while a separate trial reported an excess number of haemorrhagic strokes in the vitamin E group compared with placebo – 39 versus 23 events, indicating a hazard ratio of 1.74, 95% CI 1.04 to 2.91. In comparisons of beta carotene with placebo, the average treatment and follow up durations were between 6 and 12 years showing that data for 22,083 participants indicated no evidence of protection against AMD, risk ratio 1.00, 95% CI 0.88 to 1.14. In one study, beta-carotene appeared to be associated with an increased risk of lung cancer in people that smoked. Finally, in a male only study of vitamin C versus placebo among 14,236 participants, where AMD was assessed by self reporting followed by nedical record review, there was again no evidence for any benefit from vitamin C use. The average treatment and duration of the study was 8 years for vitamin C and 11 years for multivitamin. In addition, as in other studies, there appeared to be a slight increased risk of any AMD (risk ratio 1.21, 95% CI 1.02 to 1.43) and late AMD (risk ratio 1.22, 95% CI 0.88 to 1.69) in the multivitamin group.

 

In concluding their study, the authors stated that, “taking vitamin E or beta-carotene supplements will not prevent or delay the onset of AMD. The same probably applies to vitamin C and the multivitamin (Centrum Silver) investigated in the one trial reported to date. There is no evidence with respect to other antioxidant supplements, such as lutein and zeaxanthin. Although generally regarded as safe, vitamin supplements may have harmful effects, and clear evidence of benefit is needed before they can be recommended.”

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