The Effect of Palm Oil on Health Outcomes: A Protocol for Systematic Reviews and Meta-analyses of Controlled Clinical Trials

Background: It is suggested that palm oil consumption might increase chronic diseases including cardiovascular disease. Previous studies that investigated the effect of palm oil intake on anthropometric measures, blood glucose control, inflammation, and oxidative stress markers have led to inconsistent results. This is while no systematic review and meta-analysis has been performed to summarize the data in this regard. Objectives: The present study describes a protocol for a range of systematic reviews and meta-analyses to examine the effect of palm oil intake on body weight and fat, inflammatory markers, oxidative stress, liver enzymes, blood pressure, and blood glucose control indices. Methods: ISI web of science, EMBASE, MEDLINE, Scopus, and Google Scholar will be searched using medical subject heading (MeSH) and non-MeSH keywords. Controlled clinical trials will be selected based on predefined eligibility criteria. The intra-study risk of bias will be checked by using the Cochrane collaboration tool. Mean difference (MD) (the difference between mean change values in the intervention group/period and control group/period) and its corresponding standard deviation will be calculated to be used as effect size. A random-effects meta-analysis will be performed to pool the results. Subgroup analysis and meta-regression will be conducted to explore the possible sources of heterogeneity. Sensitivity analysis will be conducted by removing the studies one-by-one from the overall analyses. Publication bias will be assessed by inspecting funnel plots and asymmetry tests. Conclusion: The results of systematic reviews and meta-analyses might provide helpful data about the effects of palm oil consumption on different aspects of health among adults. The evidence provided by the results of systematic reviews can be useful for dietitians, clinicians, public health policy-makers, and the public.