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Maresc vitaminele riscul decesului ?

posted Jan 25, 2011, 1:36 AM by Mihai Orleanu   [ updated Jan 25, 2011, 2:04 AM ]

Some antioxidant supplements may increase the risk of death

Many people take vitamin supplements in the belief that this will improve their health and wellbeing. However, some of those supplements may actually prove to be dangerous. An analysis of previous studies suggests that the antioxidant supplements beta carotene, vitamin A and vitamin E may increase the risk of death.

Show Transcript 5 March 2007 Transcript - This transcript was typed from a recording of the program. The ABC cannot guarantee its complete accuracy because of the possibility of mishearing and occasional difficulty in identifying speakers.
Articolul care sta la baza acestui interviu: Surviving Antioxidant Supplements

Norman Swan: Welcome to the program. This morning on the Health Report the importance of fractured bones and how in some circumstances they can be foretelling your future.

How an antioxidant supplement might help people with HIV AIDS and how other antioxidants may be linked to a higher risk of death in the general public and people with certain conditions.

A study published a few days ago in the Journal of the American Medical Association has produced angry responses from the vitamin industry. A group of Danish researchers analysed the available evidence on antioxidant supplements and found that several of them are associated with an increased chance of dying prematurely.

One of the team is Dr Christian Gluud who's head of the Copenhagen Trial Unit at Copenhagen University. The thing to note here is that Dr Gluud's study isn't the first to make such a finding.

Christian Gluud: No there's been several systematic reviews and meta analyses showing that you either do not obtain any benefits from antioxidant supplements or that you may bring on hazzards by taking them. And actually we did one of the first systematic reviews on the topic back in 2004 where we looked at all the antioxidants that we had looked at now, that's beta-carotene, vitamin A, vitamin E, vitamin C and selenium and at that time we focused on all the files that addressed the question can these supplements reduce the risk of cancers in the gastro intestinal tract.

What we found at that time was that there wasn't any benefit on cancer development in the gastro intestinal tract, and the liver, and the pancreas however we saw a trend towards an increased all cause mortality. And when we focused on the trials with good methodology, that is trials with low risk of bias, we saw to our surprise a significant increase in all cause mortality.

Norman Swan: And we should just explain some of the techniques by which you analyse these trials is that you surveyed the medical literature, scientific literature, you find the trials then you cast an eye over them, or more than an eye over them in terms of their quality, how big they were, how well the statistics were, how well people were randomised. All those sorts of technical things and then you either throw out trials that are just rubbish or you can also do what you've just suggested which is that there are some trials that might be more accurate because of the way they were designed. And what you're saying here is when you lumped them all together when you were looking for gastro intestinal cancer there was a little bit of a suggestion of mortality but when you got the better quality trials which were less likely to be in error, they panned out to have a higher mortality rate.

Christian Gluud: Exactly.

Norman Swan: So this time you've looked at what - everything, any use of antioxidants?

Christian Gluud: Yeah, what we were accused of last time was maybe hitting what we call a random error because we hadn't looked at all the trials that were available. So we decided to go forth with looking at all trials that included either healthy participants or people having had a diagnosis of some sort of disease but weren't acutely ill any longer.

Norman Swan: This might would be things like - there was a trial for example of beta carotene in smokers to prevent lung cancer and there have been all sorts of trials with dementia and heart disease and things like that.

Christian Gluud: Yeah, a lot of trials. I think we have included around ten or eleven trials and people having some sort of gastro intestinal disease also that number with people having had cardiovascular disease, and six trials with neurological diseases and coupled with occular diseases and then a number of smaller groups of trials or unspecified diseases. Those were grouped under secondary prevention while the large group of participants came from what we call healthy participants, people walking along the street.

Norman Swan: And that's primary prevention where you're giving them vitamins in the hope that you'll prevent disease in the first place and secondly prevention is you've already got it and you're stopping it from getting worse.

Christian Gluud: Exactly.

Norman Swan: What did you find? First of all you've got about 70 trials didn't you with about 230,000 people

Christian Gluud: Yes, it's one of the more intensely researched topics in the world and there has been an enormous interest in this topic during the last 17 to 20 years and all the trials have been reasonably published and I must stress from the very beginning we have only been able to address what was in the published literature. But we have written direct mails to all the authors and asked them for further information and in the 68 trials that we were able to include we saw where we looked at all the antioxidant supplements together no significant harm but also no significant benefit. And then when we redid the subdivision of the trials into a group of trials with low risk of bias that is the highest methodological standard that you are able to find in the world, we see in that group that some of the supplements do harm. We see an increased mortality from beta carotene that's around 7%, from vitamin A that's around 16% increased mortality, and from vitamin E that's around 4% increased mortality. And all those figures are due to the huge number of participants - significant.

Norman Swan: So vitamin A was the top of the league?

Christian Gluud: Vitamin A seemed to cause the greatest harm.

Norman Swan: Now beta carotene was shown to increase lung cancer in smokers, if you eliminate that particular trial from the beta carotene story does it still increase mortality?

Christian Gluud: We haven't done specifically that sub-group analysis but that trial is involved. But as far as I remember this trial is not that big that it will change our results because when you reach the number of participants that you have here, you have very, very stable estimates and to take out one or two trials does not really rock the boat.

Norman Swan: And vitamin C and selenium got a clean bill of health?

Christian Gluud: No, I wouldn't say that. It is too early to say that. If you look at vitamin C the verdict is still hanging and I know that there are several trials in the world going on right now and I think we've got to see what they come up with before we have a final estimate on benefits and harm.

Norman Swan: And selenium?

Christian Gluud: Selenium - there we saw if you included all the trials, also the trials that may contain bias, there we saw a significant benefit from it. But it was very close to not being significant and if we excluded the trials that are likely biased we don't see any significant effect any more. But yet again the trials that are conducted with selenium at the moment I think they should continue because we also need more evidence there.

Norman Swan: And is it all causes of death or do some causes dominate?

Christian Gluud: We haven't seen a new way of dying. It's not that these anti oxidant supplements give you a new cause of death so to speak. The most likely is that we see an acceleration of atherosclerotic vascular diseases and an acceleration of cancer and that could be the mechanism.

Norman Swan: So your working hypothesis is that you're sitting in your motor vehicle of fate, heading for your fate, and antioxidants just put the foot on the gas a bit more than would otherwise be?

Christian Gluud: Yep.

Norman Swan: What's the take away message then - throw out the pills?

Christian Gluud: I would go back to the store where I bought them and ask them to destroy them because you shouldn't pollute the oceans with it, you do have to take care they are not non-toxic. That's one take home message but I think we should try and get something positive out of this and one of the positive things I think we could get out of it is first of all to request that anything being sold to consumers should be well tested before we start the marketing campaigns. And that also goes for vitamins, I think we've been up too early with marketing that it was good to take these things and that creates the furore that we face right now because people say oh, it can't be, we have heard for 10/20 years that it works well. It doesn't seem to work well according to our research.

Secondly I think it's mandatory that all governments now really get out of their chairs and do require that we get a registration of trials so that we are able to find it. It has taken us years to reach this conclusion and it's been very, very difficult to identify all the trials and to find out which publications of trials were actually on the same group of patients. These 68 trials were published in no less than 385 different publications.

Norman Swan: So some academics are getting their maximum mileage out of them.

Christian Gluud: There are some marketing people also within the academic circle for sure.

Norman Swan: And when you're talking about clinical trial registration here you're talking about this move towards trials having to be registered when they're started so you can actually track them much more accurately?

Christian Gluud: Exactly.

Norman Swan: I've already had my first email from a large manufacturer in Australia of vitamin supplements, what sort of criticism have you had in Europe?

Christian Gluud: Yesterday I had a number of calls from the United States and there the message I got was the very same that the manufacturers weren't happy and I do understand that they are annoyed by our results. The only thing I can say to people criticising this - please come up with better evidence. If they can mount a systematic review following the same strict way of doing it as we have tried to, I'll be happy to see other results of course. But I fear they will have difficulties doing that.

Norman Swan: Dr Christian Gluud who's Head of the Copenhagen Trial Unit at Copenhagen University in Denmark. And you're listening to the Health Report here on ABC Radio National.


Bjelakovic G et al. Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary Prevention, Systematic Review and Meta-analysis. JAMA, February 28, 2007;297;842-857


Dr Christian Gluud
Head of the Copenhagen Trial Unit Copenhagen University Copenhagen Denmark


Norman Swan


Brigitte Seega

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