A new study published in the BMJ (funded by WHO) is a meta-analysis of previous published results. These kinds of studies are an attempt to review existing data and scrutinise them for any bias and assess the integrity of the conclusions. The results can then be pooled together to draw conclusions, if possible, from a broader set of data.

I have quoted the objectives and conclusions of the study below. Feel free to have a look at the original study and think about it for yourself.

Objective To systematically review associations between intake of saturated fat and trans unsaturated fat and all cause mortality, cardiovascular disease (CVD) and associated mortality, coronary heart disease (CHD) and associated mortality, ischemic stroke, and type 2 diabetes.

Conclusions Saturated fats are not associated with all cause mortality, CVD, CHD, ischemic stroke, or type 2 diabetes, but the evidence is heterogeneous with methodological limitations. Trans fats are associated with all cause mortality, total CHD, and CHD mortality, probably because of higher levels of intake of industrial trans fats than ruminant trans fats. Dietary guidelines must carefully consider the health effects of recommendations for alternative macronutrients to replace trans fats and saturated fats.

A summary of the work is also provided after the article:

What is already known on this topic

  • Contrary to prevailing dietary advice, authors of a recent systematic review and meta-analyses claim that there is no excess cardiovascular risk associated with intake of saturated fat, and the US has recently taken policy action to remove partially hydrogenated vegetable oils from its food supply

  • Population health guidelines require a careful review and assessment of the evidence of harms of these nutrients, with a focus on replacement nutrients

What this study adds

  • This study reviewed prospective observational studies and assessed the certainty of the associations with GRADE methods

  • There was no association between saturated fats and health outcomes in studies where saturated fat generally replaced refined carbohydrates, but there was a positive association between total trans fatty acids and health outcomes

  • Dietary guidelines for saturated and trans fatty acids must carefully consider the effect of replacement nutrients

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