Introduction:
Palm oil is among the most commonly consumed cooking oils worldwide and, in contrast to most other vegetable oils, contains a high amount of saturated fatty acids. It has been suggested that palm oil has unique characteristics resulting in less detrimental effects on blood lipids than expected from its fat content. We therefore evaluated the effect of palm oil consumption on blood lipid concentrations as compared with vegetable oils high in natural unsaturated fatty acids, partially hydrogenated vegetable oils (rich in
trans
-fat), or animal fats.
Methods:
We searched PubMed, the Cochrane Library, Scopus, ProQuest, and Web of Science databases up to 31 October 2012 for trials of at least 2 weeks that compared the effects of palm oil consumption with at least one of the aforementioned comparison oils. Data on effects on total, LDL and HDL cholesterols and triglycerides were pooled using random effects meta-analysis.
Results:
A total of 25 studies were identified comparing palm oil with natural highly unsaturated vegetable oils. Palm oil significantly increased total cholesterol by 0.32 mmol/L (95% CI: 0.19, 0.44; I
2
=85.9%), increased LDL cholesterol by 0.20 mmol/L (95% CI: 0.09, 0.32; I
2
=82.9%), and increased HDL cholesterol by 0.02 mmol/L (95% CI: 0.01, 0.04; I
2
=56%) as compared with control oils. The considerable amount of heterogeneity in study results were partly explained by the type of control oil used, funding source, geographical location, and level of intake of test oil. Statistical tests suggested that this meta-analysis might be subject to publication bias.
Eight studies were identified comparing palm oil with partially hydrogenated vegetable oils. When compared to
trans
-fat rich oils, palm oil significantly increased HDL cholesterol by 0.07 mmol/L (95% CI: 0.05, 0.09; I
2
=19.2%). However, palm oil did not significantly change total cholesterol (0.15 mmol/L, 95% CI: -0.04, 0.33), LDL cholesterol (0.11 mmol/L, 95% CI: -0.04, 0.27), or triglycerides (-0.02 mmol/L, 95% CI: -0.12, 0.07). Geographical location, method of preparation of test oils, and level of intake of
trans
-fat in control intervention were contributors to the heterogeneity in the study results.
The pooled results from the 2 studies on comparison between palm oil and animal fats did not show a significant difference between the two dietary groups for total cholesterol (0.00 mmol/L, 95% CI: -0.08, 0.08), LDL cholesterol (-0.01 mmol/L, 95% CI: -0.08, 0.07), HDL cholesterol (0.00 mmol/L, 95% CI: -0.03, 0.04), or triglycerides (0.02 mmol/L, 95% CI: -0.15, 0.17).
Conclusions:
Palm oil consumption results in higher LDL cholesterol levels than other natural unsaturated vegetable oils. However, palm oil may be preferable to
trans
-fat rich oils based on its effect on HDL cholesterol. More studies are needed to evaluate the effects of palm oil consumption on incidence of coronary heart diseases.
Palm Oil Use in North Africa and West Asia