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Which oils or fats have the best effect on cholesterol?

Different oils and fats can have very different effects on blood lipids. This network meta-analysis explored exactly how different the effects are.

Study under review: Effects of oils and solid fats on blood lipids: a systematic review and network metaanalysis

Introduction

Improving one’s blood lipid profile is an important factor in reducing[1] the risk of cardiovascular disease (CVD), which is the leading cause[2] of death worldwide. In particular, reductions in LDL-cholesterol[3] (LDL-C) are strongly linked[4] to a reduction in CVD risk. Apolipoprotein B (ApoB), the protein component of atherosclerotic lipoprotein particles (like LDL, but also VLDL and chylomicron remnants), is a more predictive biomarker[5][6] of CVD than LDL-C, but is not currently measured as part of a routine blood lipid panel. Similarly, a low HDL-C level[3] is associated with increased CVD risk, but it is unclear if the relationship is causal because increasing HDL-C with drugs[7] doesn’t reduce risk. There is uncertainty about whether high triglyceride (TG) levels[8] are a useful predictor of CVD risk, as this association is weakened when other factors, such as HDL-C, are adjusted for.

There is evidence that replacing dietary saturated fat (SFA) with unsaturated fat reduces LDL-C and cardiovascular risk[9]. A particularly large LDL-C-reducing effect has been found when SFA is replaced with polyunsaturated fat (PUFA)[10]. However, this is not observed when SFA is replaced with refined carbohydrate[11]. Although olive oil is high in monounsaturated fat (MUFA) rather than PUFA, observational studies report a strong link between olive oil consumption[12] and reduced CVD risk. This may be due to the polyphenols (natural chemicals often associated with health benefits) found in olive oil, which protect LDL particles[13] from oxidative damage and interrupt the pathway in which LDL-C increases CVD risk. Furthermore, MUFA has favorable effects[14] on blood lipid levels, compared to SFA.

Therefore, current public health advice[15] in relation to oils and fats is to choose oils that are high in PUFA (such as sunflower oil, safflower oil, canola oil, corn oil, soybean oil, flaxseed oil, and walnut oil) or MUFA (such as olive oil, rapeseed oil, and peanut oil), and to limit fats high in SFA (such as butter, lard, beef fat, coconut oil, and palm oil).

But it isn’t clear exactly how these oils compare to each other. Previous trials have restricted their comparisons to only a few types[16][17][18] of fats or oils. The meta-analysis under review is the first to simultaneously compare the effects of 13 different oils and solid fats on a blood lipid profile.

Replacing dietary saturated fat with unsaturated fat (particularly PUFA) has been shown to trigger reductions in blood lipid levels, which have been linked to reductions in CVD risk. Previous research has examined the effects of consuming different types of oils and fats on blood lipids, but this is the first study to simultaneously compare the effect of 13 different oils and fats on blood lipid profiles.

Who and what was studied?

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What does this study really tell us?

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The big picture

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Frequently asked questions

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Other Articles in Issue #47 (September 2018)