Randomised trial of coconut oil, olive oil or butter on blood lipids and other cardiovascular risk factors in healthy men and women

BMJ Open

Mar 2018

DOI: 10.1136/bmjopen-2017-020167

Citations:157

Influential Citations:8

Interventional (Human) Studies

Enhanced Details

Methods

Randomised parallel-group clinical trial conducted in the general community in Cambridgeshire, UK (June–July 2017). Participants were adults aged 50–75 years without cancer, cardiovascular disease or diabetes and not on lipid-lowering medication; 96 randomised, 94 baseline assessments, 91 completed follow-up; two withdrawals; two-thirds women; 98% European Caucasian.

Intervention

Consume 50 g daily for 4 weeks of one of: extra virgin coconut oil, unsalted butter, or extra virgin olive oil; may be substituted for other fats or taken as a supplement within usual diet.

Results

Butter increased LDL-C more than coconut oil and olive oil over 4 weeks (approx +0.38–0.42 mmol/L); coconut oil did not differ from olive oil for LDL-C and slightly lowered LDL-C vs baseline. Coconut oil significantly increased HDL-C compared with butter or olive oil. Butter increased TC/HDL-C ratio and non-HDL-C versus coconut oil. No significant differences between groups for weight, BMI, central adiposity, fasting glucose or blood pressure; coconut oil reduced C-reactive protein vs olive oil. In practical terms, olive oil remains favorable for LDL-C; coconut oil behaves more like olive oil for LDL-C and raises HDL-C more than butter, suggesting effects depend on fatty acid profiles and food matrix; findings do not modify general guidance to reduce saturated fat but highlight nuanced relationships and the need for further study.

Limitations

Short 4-week duration; not blinded to the intervention; pragmatic design with no control of total energy intake; no objective biomarker of fat adherence (no blood fatty acid profiling); highly selected BBC-recruited volunteers which may limit generalisability; results address intermediate lipid markers rather than clinical outcomes.

Abstract

Introduction High dietary saturated fat intake is associated with higher blood concentrations of low-density lipoprotein cholesterol (LDL-C), an established risk factor for coronary heart disease. However, there is increasing interest in whether various dietary oils or fats with different fatty acid profiles such as extra virgin coconut oil may have different metabolic effects but trials have reported inconsistent results. We aimed to compare changes in blood lipid profile, weight, fat distribution and metabolic markers after four weeks consumption of 50 g daily of one of three different dietary fats, extra virgin coconut oil, butter or extra virgin olive oil, in healthy men and women in the general population. Design Randomised clinical trial conducted over June and July 2017. Setting General community in Cambridgeshire, UK. Participants Volunteer adults were recruited by the British Broadcasting Corporation through their websites. Eligibility criteria were men and women aged 50–75 years, with no known history of cancer, cardiovascular disease or diabetes, not on lipid lowering medication, no contraindications to a high-fat diet and willingness to be randomised to consume one of the three dietary fats for 4 weeks. Of 160 individuals initially expressing an interest and assessed for eligibility, 96 were randomised to one of three interventions; 2 individuals subsequently withdrew and 94 men and women attended a baseline assessment. Their mean age was 60 years, 67% were women and 98% were European Caucasian. Of these, 91 men and women attended a follow-up assessment 4 weeks later. Intervention Participants were randomised to extra virgin coconut oil, extra virgin olive oil or unsalted butter and asked to consume 50 g daily of one of these fats for 4 weeks, which they could incorporate into their usual diet or consume as a supplement. Main outcomes and measures The primary outcome was change in serum LDL-C; secondary outcomes were change in total and high-density lipoprotein cholesterol (TC and HDL-C), TC/HDL-C ratio and non-HDL-C; change in weight, body mass index (BMI), waist circumference, per cent body fat, systolic and diastolic blood pressure, fasting plasma glucose and C reactive protein. Results LDL-C concentrations were significantly increased on butter compared with coconut oil (+0.42, 95% CI 0.19 to 0.65 mmol/L, P<0.0001) and with olive oil (+0.38, 95% CI 0.16 to 0.60 mmol/L, P<0.0001), with no differences in change of LDL-C in coconut oil compared with olive oil (−0.04, 95% CI −0.27 to 0.19 mmol/L, P=0.74). Coconut oil significantly increased HDL-C compared with butter (+0.18, 95% CI 0.06 to 0.30 mmol/L) or olive oil (+0.16, 95% CI 0.03 to 0.28 mmol/L). Butter significantly increased TC/HDL-C ratio and non-HDL-C compared with coconut oil but coconut oil did not significantly differ from olive oil for TC/HDL-C and non-HDL-C. There were no significant differences in changes in weight, BMI, central adiposity, fasting blood glucose, systolic or diastolic blood pressure among any of the three intervention groups. Conclusions and relevance Two different dietary fats (butter and coconut oil) which are predominantly saturated fats, appear to have different effects on blood lipids compared with olive oil, a predominantly monounsaturated fat with coconut oil more comparable to olive oil with respect to LDL-C. The effects of different dietary fats on lipid profiles, metabolic markers and health outcomes may vary not just according to the general classification of their main component fatty acids as saturated or unsaturated but possibly according to different profiles in individual fatty acids, processing methods as well as the foods in which they are consumed or dietary patterns. These findings do not alter current dietary recommendations to reduce saturated fat intake in general but highlight the need for further elucidation of the more nuanced relationships between different dietary fats and health. Trial registration number NCT03105947; Results. show less