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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.