Re: Mortality in randomized trials of antioxidant supplements
- From: bigvince <Vince.Miraglia@xxxxxxxxx>
- Date: 15 May 2007 18:41:23 -0700
On May 15, 7:17 pm, William Wagner <not-to-here-william...@xxxxxxxxx>
wrote:
"CONCLUSIONS: Treatment with beta carotene, vitamin A, and vitamin E may
increase mortality. The potential roles of vitamin C and selenium on
mortality need further study."
................................
JAMA. 2007 Feb 28;297(8):842-57.
Links
Mortality in randomized trials of antioxidant supplements for primary
and secondary prevention: systematic review and meta-analysis.
€ Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C.
The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Center for
Clinical Intervention Research, Copenhagen University Hospital,
Rigshospitalet, Copenhagen, Denmark. gor...@xxxxxxxxxxxxxx
CONTEXT: Antioxidant supplements are used for prevention of several
diseases. OBJECTIVE: To assess the effect of antioxidant supplements on
mortality in randomized primary and secondary prevention trials. DATA
SOURCES AND TRIAL SELECTION: We searched electronic databases and
bibliographies published by October 2005. All randomized trials
involving adults comparing beta carotene, vitamin A, vitamin C (ascorbic
acid), vitamin E, and selenium either singly or combined vs placebo or
vs no intervention were included in our analysis. Randomization,
blinding, and follow-up were considered markers of bias in the included
trials. The effect of antioxidant supplements on all-cause mortality was
analyzed with random-effects meta-analyses and reported as relative risk
(RR) with 95% confidence intervals (CIs). Meta-regression was used to
assess the effect of covariates across the trials. DATA EXTRACTION: We
included 68 randomized trials with 232 606 participants (385
publications). DATA SYNTHESIS: When all low- and high-bias risk trials
of antioxidant supplements were pooled together there was no significant
effect on mortality (RR, 1.02; 95% CI, 0.98-1.06). Multivariate
meta-regression analyses showed that low-bias risk trials (RR, 1.16; 95%
CI, 1.05-1.29) and selenium (RR, 0.998; 95% CI, 0.997-0.9995) were
significantly associated with mortality. In 47 low-bias trials with 180
938 participants, the antioxidant supplements significantly increased
mortality (RR, 1.05; 95% CI, 1.02-1.08). In low-bias risk trials, after
exclusion of selenium trials, beta carotene (RR, 1.07; 95% CI,
1.02-1.11), vitamin A (RR, 1.16; 95% CI, 1.10-1.24), and vitamin E (RR,
1.04; 95% CI, 1.01-1.07), singly or combined, significantly increased
mortality. Vitamin C and selenium had no significant effect on mortality.
CONCLUSIONS: Treatment with beta carotene, vitamin A, and vitamin E may
increase mortality. The potential roles of vitamin C and selenium on
mortality need further study.
PMID: 17327526 [PubMed - indexed for MEDLINE]
--
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This article is posted under fair use rules in accordance with
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The Gold standard for meta-analysis is the Cocrane analysis the rules
are set in advance and are followed ' Other meta-analysis set there
own rules this is not a cocrane This meta-analysis has some serious
flaws. The authors claim to be examining the effect of these vitamins
on all cause mortality but they did not include several hundred
studies why because there were no deaths. So after they 'selected '
there studies they had 68 .From Medpage today "Some Antioxidant
Supplements Linked to Lethality " FEB. 27 2007 ' COPENHAGEN, Feb.
27 -- The antioxidant supplements beta carotene and vitamins A and E
have a dark side, carrying an increased risk of all-cause mortality,
according to a meta-analysis of 68 randomized trials. ' but as you
look at the data you find that's not exactly true because from the
same article
"When supplement risks from all low- and high-quality trials were
pooled, there was no significant effect on mortality (RR, 1.02; 95%
CI, 0.98-1.06), the researchers reported. " No effect on mortality .
Obviously this was not the right answer so they divided the group
into High Bias and Low bias studies how ? Now they get the answer
they want. I encourage anyone interested in this to read the full
JAMA article the medscape link is here
http://www.medpagetoday.com/PrimaryCare/AlternativeMedicine/tb/5152
Fuller examination of the methods here is at Highlight Health March 19
2007 "Study Showing Antioxidant Vitamins Increase Mortality Flawed"
March 19, 2007 link
http://www.highlighthealth.com/health-news/study-showing-antioxidant-vitamins-increase-mortality-flawed/
Thanks Vince
.
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