Palm Oil and Blood Lipid-related Markers of Cardiovascular Disease: A Systematic Review and Meta-analysis of Dietary Intervention Trials
Elena Fattore, Cristina Bosetti, Furio Brighenti, Carlo Agostoni, and Giovanni Fattore

Palm oil (PO) may be a potentially unhealthy fat because of its high saturated fatty acid content. 
In order to assess the effect of substituting PO for other primary dietary fats on blood lipid-related markers of coronary heart disease (CHD) and cardiovascular disease (CVD), we performed a systematic review and meta-analysis of dietary intervention trials. Studies were eligible if they included original data comparing PO-rich diets with other fat-rich diets and analyzed at least one of the following CHD/CVD biomarkers:  total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), TC/HDL-C and LDL-C/HDL-C ratios, triacylglycerols (TAGs), apolipoprotein (Apo) AI and B, very low-density lipoprotein cholesterol, and lipoprotein (a). 
Fifty-one studies were included in the meta-analysis, with intervention times ranging from 2 to 16 weeks and different fat substitutions ranging from 4 to 43%. When comparing PO diets with diets rich in stearic acid, monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs), significant higher TC, LDL-C, Apo B, HDL-C, and Apo AI were found, whereas most of the same biomarkers were significantly lower when compared with diets rich in myristic/lauric acid. Comparing PO-rich diets versus diets rich in trans fatty acids, significant higher concentrations of HDL-C and Apo AI and significant lower concentrations of Apo B, TAGs, and TC/HDL ratio were observed. Stratified and meta-regression analyses showed that the higher concentrations of TC and LDL-C, when PO was substituted for MUFAs and PUFAs, were not significant in young people and in subjects with diets with a lower percentage of energy from fat. 
In conclusion this study showed that both favorable and unfavorable changes in CHD/CVD risk markers occurred when PO was substituted for the primary dietary fats, whereas only favorable changes occurred when PO was substituted for trans fatty acids. Additional studies are needed to provide guidance for policy-making.