The "butter is good" study has some serious flaws

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  1. newliminted

    I only need to taste butter to know that it is good.

  2. awjt

    My thoughts, as well. All metas have a set of inclusion/exclusion criteria. If two studies were left out of an analysis of more than 70, then there must have been a reason. Same for the third one that was "misinterpreted."

    This after-the-fact gyrating is shoddy reporting.

    And this stupid article never answered the real question: if the three studies were re-included in the meta-analysis, did that significantly change the results? Come on. Help us out here. I want to know if I should fry that steak or pour myself a bowl of Lucky Charms.

    OK, update: I will find the original paper, read it and report back. Apparently, there is another big clinical trial that came out so recently that it wasn't in the meta-analysis. So that makes 4 more trials. I will try to formulate an opinion.

    cueing Jeopardy music...........

    We can do this from the abstract (I don't feel like paying 20 bucks for the article!):

    Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk: A Systematic Review and Meta-analysis

    Rajiv Chowdhury, MD, PhD, et al.

    Background: Guidelines advocate changes in fatty acid consumption to promote cardiovascular health.

    Purpose: To summarize evidence about associations between fatty acids and coronary disease.

    Data Sources: MEDLINE, Science Citation Index, and Cochrane Central Register of Controlled Trials through July 2013.

    Study Selection: Prospective, observational studies and randomized, controlled trials.

    Data Extraction: Investigators extracted data about study characteristics and assessed study biases.

    Data Synthesis: There were 32 observational studies (512 420 participants) of fatty acids from dietary intake; 17 observational studies (25 721 participants) of fatty acid biomarkers; and 27 randomized, controlled trials (105 085 participants) of fatty acid supplementation. In observational studies, relative risks for coronary disease were 1.03 (95% CI, 0.98 to 1.07) for saturated, 1.00 (CI, 0.91 to 1.10) for monounsaturated, 0.87 (CI, 0.78 to 0.97) for long-chain ω-3 polyunsaturated, 0.98 (CI, 0.90 to 1.06) for ω-6 polyunsaturated, and 1.16 (CI, 1.06 to 1.27) for trans fatty acids when the top and bottom thirds of baseline dietary fatty acid intake were compared. Corresponding estimates for circulating fatty acids were 1.06 (CI, 0.86 to 1.30), 1.06 (CI, 0.97 to 1.17), 0.84 (CI, 0.63 to 1.11), 0.94 (CI, 0.84 to 1.06), and 1.05 (CI, 0.76 to 1.44), respectively. There was heterogeneity of the associations among individual circulating fatty acids and coronary disease. In randomized, controlled trials, relative risks for coronary disease were 0.97 (CI, 0.69 to 1.36) for α-linolenic, 0.94 (CI, 0.86 to 1.03) for long-chain ω-3 polyunsaturated, and 0.86 (CI, 0.69 to 1.07) for ω-6 polyunsaturated fatty acid supplementations.

    Limitation: Potential biases from preferential publication and selective reporting.

    Conclusion: Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.

    ----------------------------> a few words.......

    My opinion is that the media rage was uncalled for. Just look at the RR's and confidence intervals. They had nearly 3/4 of a million study participants! That's a huge HUGE meta. These relative risks that hover around 1 mean there is no appreciable difference in measurable outcomes between the different kinds of diets. With a sample size that large, the math is accurate, and what it's telling you is that the observed differences are due to chance.

    Now, include a few more studies... or slide a few over from one column to another... most likely these will not change the results much. Or if they do, the RR's are still going to hover around 1.

    Do we want new dietary guidelines based on a 1% difference by including a few more trials? No. We don't.

    But all of this is informative. It tells us that there is a lot more going on with Coronary disease than just diet, as measured by fatty acids here in this meta. This meta clearly indicates there are other confounders at play, such as exercise, comorbidities like diabetes, personal physiology and genetics, smoking status, family history, environmental exposures, possibly specific foods, drugs or other substances like salt or pesticides, etc. When a huge meta-analysis is as inconclusive as this one about the stuff it measured, that is telling you to look elsewhere to find the cause.

    Just because a meta has results that hover around no difference does not mean that there is no new information. It means that the story is deeper, and needs to be told a different way. It means that all these dietary trials that cost millions are just researchers barking up the wrong tree.

    The takeaways:
    •The howls of criticism of this meta are overblown and overrated.
    •The meta may have been "flawed," but including a few more trials or rearranging the columns wouldn't change things much.
    •More large clinical trials about fatty acids and dietary fat intake are wasteful.
    •Coronary disease is a much more complicated system than just dietary fat intake.
    •Current dietary guidelines about fat intake are based on opinion not fact.
    •We don't really know what those guidelines should be, yet.
    •We should look hard at all the possible confounders and design new trials to measure them and give this thing a fuller picture.

  3. chenille

    Therefore the Lord himself shall give you a sign; behold, a Virgin shall conceive, and bear a son, and call his name Immanuel. Butter and honey shall he eat, that he may refuse to know the evil, and choose the good.
    - Isaiah 7:14-15 (King James Version)

  4. rocketpj

    Without butter there can be no omelette, without omelette there is no breakfast. Without breakfast I am going back to bed until this is resolved.

  5. sockdoll

    I want to believe.

    I can't believe it's not.

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