Effects of coconut oil, olive oil, and butter on plasma fatty acids and metabolic risk factors: a randomised trial.

There is limited evidence on the effects of different dietary sources of fats on detailed blood fatty acids (FAs). We aimed to evaluate the effects of coconut oil, olive oil and butter on circulating FA concentrations, and examine the associations between changes in plasma FAs and changes in metabolic markers. We conducted secondary analyses in the COB (coconut oil, olive oil and butter) Trial that evaluated 96 healthy adults in a 4-week parallel randomised controlled trial of three dietary interventions: 50 g/d of extra-virgin coconut oil (n=30), extra-virgin olive oil (n=33) or unsalted butter (n=33). We measured plasma phospholipid FA concentrations (mol% of total) using gas-chromatography. Using linear regression, we estimated the effects of the interventions on changes in FAs and the associations of changes in selected FAs with changes in metabolic markers. Coconut oil doubled lauric acid (C12:0) and myristic acid (C14:0), butter increased those to a lesser extent, and olive oil reduced those. β (95% confidence interval) for changes in C12:0 comparing coconut oil to butter and olive oil were +0.04 (0.03-0.05) and +0.05 (0.04-0.06) mol%, respectively; for C14:0, +0.24 (0.17-0.32) and +0.37 (0.29-0.45), respectively. Olive oil increased oleic acid (OA) approximately by 1 mol%, while coconut oil and butter had little effect on OA. Butter increased odd-chain SFAs and trans-FAs while olive oil and coconut oil decreased them. Changes in FAs mostly showed no significant associations with changes in metabolic markers. The interventions of equal amounts of different food FA sources altered circulating FA concentrations differently.