Re: Vitamins and mortality
- From: "trigonometry1972@xxxxxxxxx |" <trigonometry1972@xxxxxxxxx>
- Date: Tue, 6 May 2008 01:12:41 -0700 (PDT)
On May 5, 9:41 pm, "Peter Moran" <pmo...@xxxxxxxxxxxxxxxx> wrote:
A recent Cochrane review of all relevant prospective randomised controlled
trials showed no beneficial effect on death rates from antioxidant
vitamins, and possible increased mortality from Vitamin A, Beta carotene and
Vitamin E supplementation.
These are unremarkable findings. They confirm a trend in nearly all the
quality studies published in recent years. The apparent benefits of a high
vitamin intake seem to be more strongly associated with a good diet than
with supplementation.
Yet this report has been met by a frenzy of denial and accusations of
unscientific behaviour by many "nutritionists" and alternative supporters.
The main accusation of these amateur scientists against the renowned
Cochrane collaboration is that the authors excluded studies in which no
subjects died. This shows a complete misunderstanding of the nature of
the data being looked at. There are at least 26 other Cochrane reviews
examining the influence of antioxidant and vitamin supplementation on
diseases ranging from cataracts to gastrointestinal tumors. This specific
study was designed to ask whether antioxidant supplements have any effect on
*overall mortality*. So, of course it was reasonable to exclude studies in
which no subjects died, in either the intervention or the control arms of
the trials. Such studies could not contribute data relevant to the
question.
Quote from the abstract-
"Background
Animal and physiological research as well as observational studies suggest
that antioxidant supplements may improve survival.
Objectives
To assess the effect of antioxidant supplements on mortality in primary or
secondary prevention randomized clinical trials."
And a summary of the study from the Cochrane site ---
No evidence to support antioxidant supplements to prevent mortality in
healthy people or patients with various diseases. Previous research on
animal and physiological models suggest that antioxidant supplements have
beneficial effects that may prolong life. Some observational studies also
suggest that antioxidant supplements may prolong life, whereas other
observational studies demonstrate neutral or harmful effects. Randomised
trials have largely been neutral. We need evidence from randomised trials to
decide if antioxidant supplements should be used for prevention.
The present systematic review includes 67 randomised clinical trials. In
total, 232,550 participants were randomised to antioxidant supplements
(beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus
placebo or no intervention. Twenty-one trials included 164,439 healthy
participants. Forty-six trials included 68111 participants with various
diseases (including gastrointestinal, cardiovascular, neurological, ocular,
dermatological, rheumatoid, renal, endocrinological, or unspecified
diseases).
Overall, the antioxidant supplements did not seem to reduce mortality. A
total of 17880 of 136,023 participants (13.1%) randomised to antioxidant
supplements and 10136 of 96527 participants (10.5%) randomised to placebo or
no intervention died. In the analyses of the trials with low risk of bias,
beta-carotene, vitamin A, and vitamin E significantly increased mortality.
There were no significant differences between the effects of antioxidant
supplements in healthy participants (primary prevention trials) or
participants with various diseases (secondary prevention trials). Randomised
trials with adequate bias control found no significant effect of vitamin C..
In some of our analyses, selenium seems to reduce mortality.
The current evidence does not support the use of antioxidant supplements in
the general population or in patients with certain diseases. The combined
evidence suggests that additional research on antioxidant supplements is
needed. The evidence on vitamin C and selenium was not conclusive. Future
trials could focus on vitamin C and selenium and should assess both
potential beneficial and harmful effects. Conduct of additional primary and
secondary prevention trials on vitamin A, beta-carotene, and vitamin E seems
questionable, at least in the dosage range examined.
The present review does not assess antioxidant supplements for treatment of
specific diseases (tertiary prevention), antioxidant supplements for
patients with demonstrated specific needs of antioxidants, or the effects of
antioxidants contained in fruits or vegetables. Further research and
systematic reviews on these types of interventions are therefore warranted..
PM
There is a need for better studies and better reporting.
The "vitamin E" the studies use is often the racemic form
or the isolated rrr-alpha form that isn't what I take.
Plus I take my high gamma E with a whopping dose
of both K1 and K2. I take vitamin C but I also have
a high intake of numerous bioflavonoids. They
talk about antioxidants and they fail to include
r alpha lipoic acid which is like discussing the solar
system and forgetting a major planet.
Nor should all trans beta-carotene and vitamin A
be conflated though while related they aren't the same
thing.
This meta analysis is just a over-glorified editoral from Poland.
.
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