The effects of coconut oil on the cardiometabolic profile: a systematic review and meta-analysis of randomized clinical trials

Background Despite having a 92% concentration of saturated fatty acid composition, leading to an apparently unfavorable lipid profile, body weight and glycemic effect, coconut oil is consumed worldwide. Thus, we conducted an updated systematic review and meta-analysis of randomized clinical trials (RCTs) to analyze the effect of coconut oil intake on different cardiometabolic outcomes. Methods We searched Medline, Embase, and LILACS for RCTs conducted prior to April 2022. We included RCTs that compared effects of coconut oil intake with other substances on anthropometric and metabolic profiles in adults published in all languages, and excluded non-randomized trials and short follow-up studies. Risk of bias was assessed with the RoB 2 tool and certainty of evidence with GRADE. Where possible, we performed meta-analyses using a random-effects model. Results We included seven studies in the meta-analysis (n = 515; 50% females, follow up from 4 weeks to 2 years). The amount of coconut oil consumed varied and is expressed differently among studies: 12 to 30 ml of coconut oil/day (n = 5), as part of the amount of SFAs or total daily consumed fat (n = 1), a variation of 6 to 54.4 g/day (n = 5), or as part of the total caloric energy intake (15 to 21%) (n = 6). Coconut oil intake did not significantly decrease body weight (MD -0.24 kg, 95% CI -0.83 kg to 0.34 kg), waist circumference (MD -0.64 cm, 95% CI -1.69 cm to 0.41 cm), and % body fat (-0.10%, 95% CI -0.56% to 0.36%), low-density lipoprotein cholesterol (LDL-C) (MD -1.67 mg/dL, 95% CI -6.93 to 3.59 mg/dL), and triglyceride (TG) levels (MD -0.24 mg/dL, 95% CI -5.52 to 5.04 mg/dL). However, coconut oil intake was associated with a small increase in high-density lipoprotein cholesterol (HDL-C) (MD 3.28 mg/dL, 95% CI 0.66 to 5.90 mg/dL). Overall risk of bias was high, and certainty of evidence was very-low. Study limitations include the heterogeneity of intervention methods, in addition to small samples and short follow-ups, which undermine the effects of dietary intervention in metabolic parameters. Conclusions Coconut oil intake revealed no clinically relevant improvement in lipid profile and body composition compared to other oils/fats. Strategies to advise the public on the consumption of other oils, not coconut oil, due to proven cardiometabolic benefits should be implemented. Registration PROSPERO CRD42018081461. Supplementary Information The online version contains supplementary material available at 10.1186/s12944-022-01685-z.

. Detailed reasons for the exclusion of studies in the full text assessment of eligibility stage 4 Table S2. Summary of randomized clinical trials investigating the effect of coconut oil intake on anthropometric profile 5 Table S3. Summary of randomized clinical trials investigating the effect of coconut oil intake on glycemic profile 10 Table S4. Summary of randomized clinical trials investigating the effect of coconut oil on arterial blood pressure 14 Table S5. Summary of randomized clinical trials investigating the effect of coconut oil on the inflammatory profile 15 Table S6. Summary of randomized clinical trials investigating the effect of coconut oil on changes in the lipid profile 17 Table S7. Grading Figure S1. Forest plot of randomized controlled clinical trials investigating the effects in body weight (kg) of coconut oil intake versus PUFA and MUFA rich oils 33 Figure S2. Forest plot of randomized controlled clinical trials investigating the effect in body weight (kg) of coconut oil versus olive oil 33 Figure S3. Forest plot of randomized controlled clinical trials investigating investigating the effect in body weight (kg) of coconut oil versus soybean oil 34 Figure S4. Forest plot of randomized controlled clinical trials investigating the effect in body weight (kg) of coconut oil versus other oils in studies carried out in women 34 Figure S5. Forest plot of the randomized controlled clinical trials investigating the effect of coconut oil versus other oils in body weight (kg) of studies conducted in Brazil 34 Figure S6. Forest plot of randomized controlled clinical trials investigating the effect of coconut oil versus other oils/fats in body weight (kg) of studies carried out in patients with overweight/obesity 35 Figure S7. Forest plot of randomized controlled clinical trials investigating the effect on body weight (kg) of coconut oil versus other oils/fats without the long term study of Vijayakumar et al. 35 Figure S8. Forest plot of randomized controlled clinical trials investigating the effect in body weight (kg) of coconut oil versus other oils/fats in studies including co-intervention 36 Figure S9. Forest plot of randomized controlled clinical trials investigating the effects in waist circumference (cm) of coconut oil intake versus PUFA and MUFA rich oils 36 Figure S10. Forest plot of randomized controlled clinical trials investigating the effect in waist circumference (cm) of coconut oil versus olive oil 37 Figure S11. Forest plot of randomized controlled clinical trials investigating the effect in waist circumference (cm) of coconut oil versus soybean oil 37 Figure S12. Forest plot of randomized controlled clinical trials investigating the effect in waist circumference (cm) of coconut oil versus other oils when analyzing studies carried out in women 37 Figure S13. Forest plot of randomized controlled clinical trials investigating the effect in waist circumference (cm) of coconut oil versus other oils when analyzing studies conducted in Brazil 38 Figure S14. Forest plot of randomized controlled clinical trials investigating the effect in waist circumference (cm) of coconut oil versus other oils or/fat in patients with overweight/obesity 38 Figure S15 -Forest plot of randomized controlled clinical trials investigating the effect in waist circumference (cm) of coconut oil versus other oils/fats in studies including co-intervention 39 Figure S16. Forest plot of the randomized controlled clinical trials investigating the effects in % body fat of coconut oil intake in comparison to other oils/fat 39 Figure S17. Forest plot of randomized controlled clinical trials investigating the effect in % body fat of coconut oil intake vs PUFA and MUFA rich oils 40 Figure S18. Forest plot of randomized controlled clinical trials investigating the effects in LDL-C (mg/dL) of coconut oil intake vs PUFA and MUFA rich oils 40 Figure S19. Forest plot of randomized controlled clinical trials investigating the effect in LDL-C (mg/dL) of coconut oil versus olive oil 40 Figure S20. Forest plot of randomized controlled clinical trials investigating the effect in LDL-C (mg/dL) of coconut oil versus soybean oil 41 Figure S21. Forest plot of randomized controlled clinical trials investigating the effect in LDL-C (mg/dL) of coconut oil versus other oils when analyzing studies carried out in women 41 Figure S22. Forest plot of randomized controlled clinical trials investigating the effect in LDL-C (mg/dL) of coconut oil versus other oils when analyzing studies conducted in Brazil in LDL-C 41 Figure S23. Forest plot of randomized controlled clinical trials investigating the effect in LDL-C (mg/dL). of coconut oil versus other oils or/fat in patients with overweight/obesity 42 Figure S24. Forest plot of randomized controlled clinical trials investigating the effect in LDL-C (mg/dL) of coconut oil versus other oils or fat without a long term study (Vijayakumar et al) 42 Figure S25. Forest plot of randomized controlled clinical trials investigating the effect in LDL-C (mg/dL) of coconut oil versus other oils or fat with co-intervention 43 Figure S26. Forest plot of randomized controlled clinical trials investigating the effects in HDL-C (mg/dL) of coconut oil intake vs PUFA and MUFA rich oils 43 Figure S27. Forest plot of randomized controlled clinical trials investigating the effect in HDL-C (mg/dL) of coconut oil versus olive oil 43 Figure S28. Forest plot of randomized controlled clinical trials investigating the effect in HDL-C (mg/dL) of coconut oil versus soybean oil 44 Figure S29. Forest plot of randomized controlled clinical trials investigating the effect in HDL-C (mg/dL) of coconut oil versus other oils when analyzing studies carried out in women 44 Figure S30. Forest plot of randomized controlled clinical trials investigating the effect in HDL-C (mg/dL) of coconut oil versus other oils when analyzing studies conducted in Brazil 44 Figure S31. Forest plot of randomized controlled clinical trials investigating the effect in HDL-C (mg/dL) of coconut oil versus other oils or fat in patients with overweight/obesity 45 Figure S32. Forest plot of randomized controlled clinical trials investigating the effect in HDL-C (mg/dL) of coconut oil versus other oils or fat without a long term study (Vijayakumar et al) 45 Figure S33. Forest plot of randomized controlled clinical trials investigating the effect in HDL-C (mg/dL) of coconut oil versus other oils or fat with co-intervention 46 Figure S34. Forest plot of randomized controlled clinical trials investigating the effects in TG (mg/dL) of coconut oil intake vs PUFA and MUFA rich oils 46 Figure S35. Forest plot of randomized controlled clinical trials investigating the effect in TG (mg/dL) of coconut oil versus olive oil 47 Figure S36. Forest plot of randomized controlled clinical trials investigating the effect in TG (mg/dL) of coconut oil versus soybean oil 47 Figure S37. Forest plot of randomized controlled clinical trials investigating the effect in TG (mg/dL) of coconut oil versus other oils when analyzing studies carried out in women 47 Figure S38. Forest plot of randomized controlled clinical trials investigating the effect in TG (mg/dL) of coconut oil versus other oils when analyzing studies conducted in Brazil 48 Figure S39. Forest plot of randomized controlled clinical trials investigating the effect in TG (mg/dL) of coconut oil versus other oils or fat in patients with overweight/obesity 48 Figure S40. Forest plot of randomized controlled clinical trials investigating the effect in TG (mg/dL) of coconut oil versus other oils or fat without a long term study (Vijayakumar et al) 48 Figure S41. Forest plot of randomized controlled clinical trials investigating the effect in TG (mg/dL) of coconut oil versus other oils or fat with co-intervention 49 Figure S42: RoB 2.0 risk of bias in RCTs assessing the effects of coconut oil in the lipid profile 50 Figure S43: RoB 2.0 risk of bias in RCTs assessing the effects of coconut oil in the anthropometric profile 51 Figure S44: RoB 2.0 risk of bias in RCTs assessing the effects of coconut oil in the glycemic profile 52 Figure S45: RoB 2.0 risk of bias in RCTs assessing the effects of coconut oil in blood pressure 53 Figure S46

Full search strategy and search terms in LILACS:
(tw:(óleo de coco)) AND (tw:(ensaio clínico)) 3 weeks n = 9 healthy men 35% of the calories of the day were derived from LIP and of these, 50% were from coconut oil, which was incorporated into muffins or biscuits. Each muffin or cookie provided 13.7 g of LIP of the oil test.

Supplementary Tables
35% of the calories of the day were derived from LIP and of these, 50% were from palm oil or hydrogenated soybean oil which was incorporated into muffins or biscuits. Each muffin or cookie provided 13.7 g of LIP of the oil test.   3 weeks n = 9 healthy men 35% of the calories of the day were derived from LIP and of these, 50% were from coconut oil, which was incorporated into muffins or biscuits. Each muffin or cookie provided 13.7g of LIP for the oil test.
35% of the calories of the day were derived from LIP and of these, 50% were from palm oil or hydrogenated soybean oil which was incorporated into muffins or biscuits. Each muffin or cookie provided 13.7g of LIP for the oil test.     c. Imprecision due to wide confidence interval: in the worst scenario, it may increase 3.59 mg/dL; in the best scenario, it may decrease 6.93 mg/dL.
A crossover study (n=9) [11] demonstrated that consumption of coconut oil increases blood glucose levels more than palm oil, but less than hydrogenated soybean oil.

HbA1c
Two studies analyzed this outcome (n=273, 32% female, 29 to 68 years) [4,14]. An 8-week study found significantly lower values of HbA1c when comparing coconut oil to PUFAs [4]. A investigating the effects of coconut oil intake vs PUFA and MUFA rich oils on fasting blood glucose (mg/dL).

Systolic Blood Pressure
Two studies [5,15] analyzed this outcome (n=126, 63% female, 20 to 66 years, follow-up of 4 to 8 weeks). When comparing the effect of coconut oil intake with placebo, higher levels of systolic blood pressure are observed [15]. However, when the effect of the intake of coconut oil is compared with olive oil or butter, lower levels of systolic blood pressure are observed [5]. We were not able to meta-analyze these data, since one study was a crossover trial and there was not enough data. Results are shown in table S3.

Diastolic Blood Pressure
Two studies [5,15] analyzed this outcome (n=126, 63% female, 20 to 66 years, follow-up of 4 to 8 weeks). When the effect of the intake of coconut oil is compared with placebo, olive oil and butter, higher levels of diastolic blood pressure are observed [5,15]. We were not able to meta-analyze these data, since one study was a crossover trial and there was not enough data. Results are shown in table S3.
Two studies [2,5] were included in the meta-analysis. Overall, the effect of coconut oil intake on US-CRP in comparison to other oils/fats did not differ (-0.04 mg/dL; 95% CI -0.91 to 0.82  Selection process 8 Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process.

Pg. 6
Data collection process 9 Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process.
Pg. 6 Data items 10a List and define all outcomes for which data were sought. Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect.
Pg. 6, 7 10b List and define all other variables for which data were sought (e.g. participant and intervention characteristics, funding sources). Describe any assumptions made about any missing or unclear information.
Pg. 6, 7 Study risk of bias assessment 11 Specify the methods used to assess risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.

Pg. 7
Effect measures 12 Specify for each outcome the effect measure(s) (e.g. risk ratio, mean difference) used in the synthesis or presentation of results. Pg. 8

Synthesis methods
13a Describe the processes used to decide which studies were eligible for each synthesis (e.g. tabulating the study intervention characteristics and comparing against the planned groups for each synthesis (item #5)).
Pg. 7 13b Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions.
Pg. 8 13c Describe any methods used to tabulate or visually display results of individual studies and syntheses. Pg. 8

Item # Checklist item
Location where item is reported 13d Describe any methods used to synthesize results and provide a rationale for the choice(s). If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.
Pg. 8 13e Describe any methods used to explore possible causes of heterogeneity among study results (e.g. subgroup analysis, meta-regression). Pg. 9 13f Describe any sensitivity analyses conducted to assess robustness of the synthesized results. Pg. 9 Reporting bias assessment 14 Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases). Pg. 7 Certainty assessment 15 Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome. Pg. 7, 8

Study selection
16a Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.
Pg. 9 and fig.  1 16b Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded. Figure 1 and Table S1 Study characteristics 17 Cite each included study and present its characteristics. Pg. 9, 10 and 19 For all outcomes, present, for each study: (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e.g. confidence/credible interval), ideally using structured tables or plots.

Figures 2 and 3
Results of syntheses 20a For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies. Pg. 10-15 20b Present results of all statistical syntheses conducted. If meta-analysis was done, present for each the summary estimate and its precision (e.g. confidence/credible interval) and measures of statistical heterogeneity. If comparing groups, describe the direction of the effect.

Figures 2 and 3
20c Present results of all investigations of possible causes of heterogeneity among study results. Pg. 9 20d Present results of all sensitivity analyses conducted to assess the robustness of the synthesized results. Pg. 9-15 Reporting biases 21 Present assessments of risk of bias due to missing results (arising from reporting biases) for each synthesis assessed. Pg. 15  Availability of data, code and other materials 27 Report which of the following are publicly available and where they can be found: template data collection forms; data extracted from included studies; data used for all analyses; analytic code; any other materials used in the review. NA