Short-term supplement of virgin coconut oil improves endothelial-dependent dilation but not exercise-mediated hyperemia in young adults

Abstract Virgin coconut oil (VCO) is high in antioxidants, which reduces reactive oxygen species-induced conversion of vascular endothelial-derived nitric oxide (NO) to toxic peroxynitrite. As such, flow-mediated dilation (FMD, a surrogate marker of NO bioavailability) and exercise-mediated hyperemia may be enhanced following VCO treatment. Animal research support these findings but direct assessments of FMD after short-term VCO use in humans is unknown. We tested the hypotheses that a 4-week VCO supplement (30 ml·day −1 ) would improve popliteal artery (PA) FMD and the hyperemic response to aerobic exercise. Thirty-four young adults were divided into VCO (n = 19, 9F, 22 ± 2 years, 24 ± 3 kg·m −2 ), and control (CON: n = 15, 7F, 24 ± 2 years, 24 ± 3 kg·m- 2 ) groups. PA-FMD and blood flow were assessed via high-resolution duplex ultrasonography (Vivid i, GE Healthcare). PA blood flow was measured at rest and for 5-minutes following a 10-minute bout of moderate-intensity (60% heart rate reserve) cycling exercise. Total PA blood volume was calculated as the integral of the 5-minute post-exercise PA blood flow response. After 4 weeks, PA-FMD increased ( P  = .04) following VCO supplementation (4.9 ± 0.9% to 5.5 ± 1.2%) with no change ( P  > .9) in the CON group (5.7 ± 2.1% to 5.8 ± 1.9%). There were no differences (both, P  > .28) in the post-exercise total PA blood volume response in either group (VCO: 495 ± 355 ml to 598 ± 384 ml; CON: 562 ± 362 ml to 488 ± 229 ml). Short-term VCO supplementation does not alter aerobic exercise-mediated blood flow responses in young adults. However, the augmented popliteal FMD response observed in the VCO supplement group indicates that short-term VCO supplementation improves vascular endothelial function in young, healthy adults.