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Macro nutrients balance and heart disease

  1. Aug 29, 2017 #1

    jim mcnamara

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    Staff: Mentor

    From meeting of cardiologists in Spain:
    Study on +135000 people worldwide, researchers interpretation:

    Note that the study included many residents of third world countries where macronutrient (fats and carbohydrates) over consumption is not common.
    For biology types:
    http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(17)32252-3/fulltext?elsca1=tlpr
    For normal humans:
    https://www.medpagetoday.com/meetingcoverage/esc/67566
     
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  3. Aug 29, 2017 #2

    Ygggdrasil

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    A few notes to keep in mind with the interpretation of the results:
    1. The macronutrient consumption data are based on food frequency questionaires, a somewhat unreliable means to measuring food consumption. How accurate do you think you'd be if asked about how much of each type of food you ate over the past few months? For more disucssion of problems with food frequency questionaires and other general issues with studies on nutrition see: http://fivethirtyeight.com/features/you-cant-trust-what-you-read-about-nutrition/

    2. The study is an observational study that can only assess correlation, not causation. People who reported eating more carbohydrates had higher mortality. Was eating more carbohydrates the cause of the higher mortality, or were there other differences between people who ate more carbohydrates and those who ate less? A common problem with these studies is that people who follow dietary guidelines are more likely to follow other guidelines for healthy living, so one could just be picking up a signal from decreased mortality of those who pay attention to their health, in general. Socioeconomic factors are another potential confounding factor in the results. In many of the third world countries studied, a diet higher in animal protein would likely be more expensive than a diet higher in carbohydrates. These confounding variables make inferring causation difficult. Randomized controlled trials would provide a gold standard for assessing whether there is a causal relationship between carbohydrate intake and mortality, though these are notoriously difficult to perform (how do you get a large cohort of people to change their diets for long periods of time?).

    3. Even if the differences in diet are causally related to the changes in mortality and CV events, the exact mechanism is unclear. For example, in a commentary published in the Lancet along side the research paper (I would recommend reading the commentary if you are interested in the subject), the authors note:
    If the results are partly due to consumption of animal products alleviating micronutrient malnutrition, it is unclear whether the results would be as applicable in populations where micronutrient malnutrition is not an issue.

    Overall, the study is a very important piece of evidence in determining the best amount of carbohydrates, proteins and fats to include in one's diet. However, it is not a definitive study, so one needs to consider the entire body of evidence including observational studies (such as this one) done in a number of different populations, randomized clinical trials, and laboratory experiments that get at the mechanisms involved.
     
    Last edited: Aug 29, 2017
  4. Sep 2, 2017 #3

    Ygggdrasil

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    Saw a good piece in The Atlantic about the study:
    https://www.theatlantic.com/health/...ate-intake-of-things-linked-to-health/538428/

    Worth a read if you are interested in the subject.
     
  5. Sep 12, 2017 #4
    I have to say, I wasn't keen on the Atlantic article, this research and other papers are essentially discrediting the last 20 years of dietary advice, and it has very real implications for the way in which poor quality epidemiology is used to support current medical opinion. In many ways public health advice hasn't moved on much from the seven deadly sins. In fact its only in very recent times that a good diet has been defined as the one with the least nutritional value in an attempt to "treat" obesity, the recognition that reducing fats isn't necessarily good for people has shifted the focus to carbohydrates, principally simple sugars. This continues despite the predicted health tsunami of increasing heart disease and shorter life expectancy failing to appear, in fact the incidence of heart disease has been falling, in a way that cannot be explained by better interventions and life expectancy continues to rise though this has slowed.
    I'm not sure why the author thinks that this is the diet of the healthiest populations, the last time I looked this would be the Swiss, depending on what measure you use and this is not a country associated with rampant vegetarianism.
    I suspect that there are a great many biases involved in the industry of public health and the promotion of specific healthy foods which influence many of the findings and there have been a fairly continuous stream of papers, challenging the role of fats in heart disease which have simply been dismissed or attacked. This one is very difficult to dismiss and if you look around any supermarket, just note how many products are labeled low fat and the economic effects of this study, we have yet to see how it will effect the drug companies as statins come under increasing scruitiny.
    I think this is far more important than the author of the Atlantic article suggests and he makes a number of sweeping statements that don't represent what the study actually suggests.
     
  6. Sep 12, 2017 #5
    These are some other studies that question the link between saturated fat and heart disease and/or mortality:

    http://www.nutrition-coalition.org/saturated-fats-do-they-cause-heart-disease/
     
  7. Sep 13, 2017 #6
    This 2017 article is an excellent piece worth reading in full. I'll quote some of hi-lites, in case you have to be a health professional to access to link:

    http://www.medscape.com/viewarticle/882564?src=soc_tw_160817-pm_mscpedt_news_neuro&faf=1#vp_1
     
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