1. GingerCoffee
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    GingerCoffee Web Surfer Girl Contributor

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    Vitamin C, the immune system and how to interpret 'conflicting' research

    Discussion in 'The Lounge' started by GingerCoffee, Jul 14, 2013.

    I've moved this from the Blue Planet thread since it was off topic:
    Do you see what you did there? Minimal and no are not the same word. I said minimally relevant. I did not say no results at all. The Linus Pauling myth is large doses of vitamin C shorten your cold. The evidence does not support that assertion. There is a minimal bit of evidence that a daily supplement might prevent some colds.


    Your link makes a dozen claims about vitamin C, much too broad a subject to address in one thread, so let's keep this to claims that large doses of vitamin C prevent viral respiratory infections or shorten their length.

    It's interesting you would link to an Institute with the name Linus Pauling. The guy was a chemist, that's what his Nobel Prize was in. Yet he's seen as a founder of the food supplement movement. People are always looking for the magic bullet. In reality we are in an arms race with the world of pathogenic microorganisms. We develop immunity, they develop a means to overcome our immunity. Any magic bullet one develops, including vitamin C if it did work, would soon be defeated by the drug resistance mechanisms of pathogens. People don't want to believe that, but genetic science easily demonstrates it. We don't have magical immune systems if only they were fine tuned. The immune system is a very good thing, it just isn't magical.

    You've cited one of several educational institutions who see their mission as proving discredited claims about food supplements, (among other things). It's not a bad thing, necessarily. It's an oft heard claim that Big Pharma controls all the research dollars and there's no profit in the billion dollar supplement industry. Only billions in profit? Hopefully it's obvious to you that profit is not the issue. Making false claims is, which is also a motive to not do the research since the research actually shows There are a few Naturopathic and Holistic health care institutions that at least recognize the importance of scientific evidence based medicine. In this neighborhood it's the Bastyr Institute.

    I applaud the mission of trying to move supplements into the scientific evidence based medicine arena. But, be it Big Pharma's influence on research, which does have serious problems that need consideration, or Naturopathic's confirmation bias which has a different set of problems, the key is to understand the significance of the research conclusions, not just find the ones that support what we already believe.


    Here's a summary:

    1) Look for research showing disease outcomes, not just support of hypothesized mechanisms of action.
    2) If a deficiency causes disease, it doesn't mean an excess enhances health.
    3) Small studies are for the most part pilot studies, they do not support conclusions, they merely say, this should be looked at.
    4) The news media incompetently reports on medical research, find the original source of a study before believing the reporter's interpretation.
    5) Studies have to be repeatable.
    6) Animal studies do not always predict effects on humans.
    7) There is a positive result bias in published medical research. (See Ben Goldacre's excellent work on this problem.)
    8) Not every study is well done. One has to consider the methodology.
    9) In addition to the positive bias in what medical research gets published, there are cultural biases to be careful of. In particular, cultures where failure and face saving are issues. This can be financial, ethnic and/or professional cultural influences.
    10) Marketing claims without FDA approval of the claim means the claim is unsupported by the evidence, it doesn't mean Big Pharma controls the FDA. People selling those supplements are making just as high of profits as Big Pharma is.
    11) Most important of all, none of this means you cannot trust scientific medical research, there are incredible successes that prove its value. It just means one needs to interpret research cautiously and intelligently. And claims are meaningless without scientific medical evidence supporting the claims.​

    So back to the vitamin C and immune system enhancement claims.

    Here's what your link says:
    Notice they assert vitamin C has an effect even though they note it doesn't, or may not. So which is it, research results are mixed or the results clearly show an effect?

    Then there is the crux of the matter, whether vitamin C affects the immune system is not what we care about. We care whether that translates into an effect on a cold:
    There's some pretty clear confirmation bias here. To say that in 60 years we still don't have enough controlled clinical trials of vitamin C and viral respiratory infections should be a red flag. Especially since they follow their own claim with a citation to those very controlled clinical trials.

    That's their summary. Best to look at the actual source: Cochrane Review- vitamin C for preventing and treating the common cold.

    So what about all those studies I didn't bold showing a reduction in the number of colds people caught?
    Well, you'd need to see what the 'modest effect' meant, and decide if it was worth taking a vitamin C supplement every day. The author of the CR didn't think the research supported daily supplements.

    Here is the CR author's actual summary of what the meta-analysis of the research showed:
    The CRs note further RCTs are warranted in just about every review summary. Scientific evidence based medicine in general lacks sufficient randomized controlled clinical trials.

    I am not opposed to taking vitamins, I take vitamin D in the winter when we have less sun around here. Before I chose to take vitamin C before physical stress, I would want to look at the studies of vitamin C supplements when one experienced extreme physical stress. Just be careful expanding that conclusion where it doesn't go, into non-extreme stress situations.


    Of course if you are the Linus Pauling Institute, taking your name from the vitamin C claims, if you don't get results that support your preconceived belief, you emphasize the fact the Cochrane Review noted inadequate clinical trials:
    Fine. If they want to keep investing in this research, more power to them.

    But it's at least time to accept that reaching for the vitamin C when one comes down with a cold isn't going to do any good. The research shows it will not shorten your illness. Taking a supplement before extreme physical stress might be evidence supported. A daily dose to prevent colds is a lot of effort for a little benefit. I'd bet that a little extra effort washing one's hands would be effort much better spent.
     
  2. maskedhero
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    maskedhero Active Member

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    I read a fascinating book on colds recently, which basically said wash your hands, and you'll still deal with it.

    http://www.npr.org/templates/story/story.php?storyId=129829134

    It went through all of the myths, and pounded each one down (except the placebo of chicken soup, apparently).

    Vitamin C wasn't as much bunk as the stuff people snort, which can lead to loss of smell.
     

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