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

Robinson, Susan A., O'Brien, Myles W., Grandy, Scott A., Heinze-Milne, Stefan, Kimmerly, Derek S.
Nutrition research 2019 v.67 pp. 17-26
animal research, antioxidants, bioavailability, blood flow, blood volume, coconut oil, exercise, heart rate, hyperemia, nitric oxide, oxygen, research support, toxicity, ultrasonography, young adults
Virgin coconut oil (VCO) is high in antioxidants, which reduce 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 supports these findings, but direct assessments of FMD after short-term VCO use in humans are unknown. We tested the hypotheses that a 4-week VCO supplement (30 mL·d−1) would improve popliteal artery (PA) FMD and the hyperemic response to aerobic exercise. Thirty-four young adults were divided into VCO (n = 19, 9 women, 22 ± 2 years, 24 ± 3 kg·m−2) and control (CON: n = 15, 7 women, 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, Mississauga, Ontario, Canada). 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 postexercise 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 postexercise total PA blood volume response in either group (VCO: 495 ± 355 to 598 ± 384 mL; CON: 562 ± 362 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.