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Badly Flawed Study of Fish Oils Leaps to Wildly Unsupported Conclusions about Cancer 7/16/13 via ANH

Discussion in 'Other Health News and Research' started by ggingues, Jul 18, 2013.

  1. ggingues

    ggingues $10 gift code at iHerb GAS343 of $40

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    The study’s authors showed similar biases in previous papers—yet the media keep stoking the flames without doing any serious analysis.

    A new study from the Fred Hutchinson Cancer Research Center, led by Theodore Brasky, PhD, et al., has supposedly found a link between high concentrations of EPA, DPA and DHA in the bloodstream—the three anti-inflammatory and metabolically related fatty acids derived from fatty fish and fish-oil supplements—and an increased risk of prostate cancer: a 44% increased risk of “low-grade” prostate cancer, and a 71% increased risk of “high grade” (that is, aggressive) cancer, according to their report.

    Brasky and his colleagues looked at two groups: their own cohort of 834 men diagnosed with prostate cancer, of which 156 had high-grade cancer; and, for comparison, the data and blood samples from 1,393 men of the same age range randomly chosen from the 35,500 participants in the prostate cancer SELECT trial. In looking at the analysis of the men’s blood samples, Brasky et al. found that men who had the highest amount of long-chain omega-3 polyunsaturated fatty acids (LCω-3PUFA) in their system had an increased risk of prostate cancer, compared to men with the lowest amount of LCω-3PUFA. At the same time, they found that omega-6 fatty acids were associated with lower risks of total prostate cancer.

    Brasky and his colleagues had published a paper in 2011 indicating that DHA was positively associated with high-grade prostate cancer, but that trans-fatty acids (like those found in margarine and frying oils that contribute to heart disease) were associated with a decreased risk of aggressive prostate cancer. This new analysis seems to confirm their previous findings.

    It’s like living in topsy-turvy land.

    Brasky’s conclusions run contrary to almost every previous study on the subject. There are several prospective studies showing numerous benefits of omega-3 fatty acids in relation to cancer. In one, researchers investigated the effect of dietary fish intake among 6,272 Swedish men who were followed for thirty years. Men who ate no fish had a two- to three-fold increase in the risk of developing prostate cancer compared with those who consumed large amounts of fish in their diet. Similar studies have suggested lower prostate cancer risk associated with omega-3 fatty acids from fish in Japanese and Brazilian men.

    An important Harvard study examined the link between dietary fish consumption and the risk of metastatic prostate cancer. The study involved 47,882 men over twelve years, and found that eating fish more than three times a week reduced the risk of prostate cancer but had an even greater impact on the risk of metastatic prostate cancer. For each additional 500 mg of marine fat consumed, the risk of metastatic disease decreased by 24%!

    Let’s look at some of the problems with the study, both with the way the study was set up and with the conclusions reached by the researchers:
    · The group Brasky used for comparison in his study were participants in SELECT (theSELenium and vitamin E Cancer prevention Trial) conducted from 2001 to 2008. The $114 million study was trying to determine whether vitamin E (in the form of incomplete and synthetic alpha-tocopherol, one of eight forms of vitamin E that in nature work together) and selenium can prevent prostate cancer. This study was called to a halt when an early look at the data showed no benefit for the treatment. In this clinical trial there were slightly more prostate cancers in men taking alpha-tocopherol vitamin E alone, and slightly more diabetes in men taking only selenium. But neither finding was statistically significant, meaning these findings were likely due to chance.
    cont'd
    http://www.anh-usa.org/flawed-study-fish-oil-cancer/
     
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  2. alex3619

    alex3619 Senior Member

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    Alpha tocopherol is not good. Why would anyone use them as a comparison group?

    Their suggestion that trans fats may have some benefit is not entirely without merit though. Trans fats are a poison, and cancer cells are vulnerable to poison. This would however mean that trans fats are being used as uncontrolled dietary chemo ... not something I would recommend for good health.

    In all cases though I want to know what the final verdict is: what were the survival rates? In big studies like this its important to highlight that, and in really big studies its very bad science to not take this into account.

    Omega-6 fats push inflammation and immune effects. Its not inconceivable that they might be beneficial if you have cancer, but that will come at a price to other aspects of health if you eat too much omega-6. So what does this do to mortality?

    Again, even with cancer: what were the survival rates? The article rightly points out that this needs to be established.

    Also, what were the causative issues? Were these people questioned about their consumption of fish or fish oil? These things might be important in how the study is interpreted. People who are having problems that might lead to cancer might be more likely to look after their health and consume more fish oil, for example. Was this ruled out? From the article it wasn't.

    What does this mean for people with inflammatory disorders? A control group containing MS or rheumatoid arthritis would be needed. In addition, many with ME have low HDL cholesterol. How does that modify the picture?

    I am not happy about the reporting of this study though, and very not happy that it is not free access. There are hints that important aspects of the paper are not being discussed. I think we need to know a lot more about this study before making reaching a final conclusion. Such issues might change the discussion. For example, I would really want to know the specifics of how the patient cohort was selected.

    One issue for example is that this study needs to be interpreted on its own merits. The authors in the abstract conclusion talk about potential risk. They are apparently not claiming that their study is definitive. Their conclusions might therefore have high scientific validity, which is quite separate from the issue of whether their interpretations are right or wrong.
     
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  3. MeSci

    MeSci ME/CFS since 1995; activity level 6

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    I had a quick read of this analysis and a lot of good points were raised.

    When I heard of/read the study in question (possibly via Physician's First Watch) it occurred to me that high plasma levels of a substance/nutrient do not necessarily indicate a high intake. It could instead indicate that the cells are unable to take up the nutrient efficiently. That could be the reason for an increased risk of some illnesses.

    ANH also comment on this, stating that red blood cell (RBC) levels would be a better indicator. In the UK, blood levels of nutrients are usually measured from plasma/serum, and anyone who wants RBC levels done has to get it done privately.
    :rolleyes:
     
  4. alex3619

    alex3619 Senior Member

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    There is no barrier to cellular absorption of omega-3 fats once its in the blood stream that I am aware of. I am not sure about selenium. If there is a problem it might be in the proper synthesis of phospholipids though. If so then the composition of the omega-3 phospholipids found might have been different from the norm. Otherwise I can see no reason to think omega-3's can't be absorbed into tissues from the blood. Now it is definitely the case that some polyunsaturated fats are not properly converted into hormones in some people. Anyone who is salicylate sensitive will have this problem. There is also an issue that oxidative stress (which we have oodles of) will damage the omega-3 fats.

    In most people a high level of omega-3 fats in their blood will mean a very different ratio of series-2 to series-3 eicosanoids being synthesized, and an improvement in nutrient transfer into cells. There also appears to be intracellular factors involved in the regulation of gene expression, but I have never looked into that and my information is now 13 years out of date on this.
     
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  5. MeSci

    MeSci ME/CFS since 1995; activity level 6

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    Good point - I had forgotten that lipophilic substances can easily cross cell membranes. Yes, maybe it is an issue with conversion, so that they are not being broken down/converted/used where they are needed.
     
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