Study under review: Effects of oils and solid fats on blood lipids: a systematic review and network metaanalysis
Improving one’s blood lipid profile is an important factor in reducing the risk of cardiovascular disease (CVD), which is the leading cause of death worldwide. In particular, reductions in LDL-cholesterol (LDL-C) are strongly linked 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 of CVD than LDL-C, but is not currently measured as part of a routine blood lipid panel. Similarly, a low HDL-C level is associated with increased CVD risk, but it is unclear if the relationship is causal because increasing HDL-C with drugs doesn’t reduce risk. There is uncertainty about whether high triglyceride (TG) levels 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. A particularly large LDL-C-reducing effect has been found when SFA is replaced with polyunsaturated fat (PUFA). However, this is not observed when SFA is replaced with refined carbohydrate. Although olive oil is high in monounsaturated fat (MUFA) rather than PUFA, observational studies report a strong link between olive oil consumption 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 from oxidative damage and interrupt the pathway in which LDL-C increases CVD risk. Furthermore, MUFA has favorable effects on blood lipid levels, compared to SFA.
Therefore, current public health advice 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 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.
Other Articles in Issue #47 (September 2018)
Betaine: Can it improve body composition and performance in women?
This is the first study to look at betaine's effects on body composition and performance in women who have just started lifting.
Smackdown: Whole grains versus fruits and vegetables effects on inflammation and the gut microbiome
Overweight and obesity can be accompanied by subclinical inflammation, which may be tied in part to the gut microbiome. This study aimed to find out how increasing fruit and veggie or whole grain intake affects these.
NERD Mini: What’s healthy about chocolate?
We summarize which health claims about chocolate have some evidence to back them up according to a recent umbrella review on the matter.
Cheese reloaded: enter the matrix
Context matters when it comes to macronutrients’ impact on lipid levels.
Gut bugs as bone drugs
What effect can probiotic supplementation have on bone density? This study aimed to find out
Fighting fat with fat: omega-3s vs. NAFLD
Diet and exercise are some of the main ways to fight non-alcoholic fatty liver disease. This meta-analysis examined whether n-3 supplementation could be added to the list.
NERD Mini: The sports supplements with the highest amount of evidence according to the ISSN
We summarize which supplements have the best evidence base for muscle building and performance enhancement according to the ISSN’s recently updated sports nutrition review.