Dietary Bioflavanol Supplementation Does Not Improve Cold-Induced Vasodilation in Healthy Adults
FASEB J. 2022 May;36 Suppl 1. doi: 10.1096/fasebj.2022.36.S1.R3395.
ABSTRACT
BACKGROUND: Cold-induced vasodilation (CIVD) is a cyclical rise in blood flow to glabrous skin that occurs during cold exposure of the extremities. Nitric oxide (NO) is a proposed mediator of the CIVD response through active vasodilation and/or withdrawal of sympathetic vascular smooth muscle tone. Dietary flavanols augment bioavailable NO by upregulating NO synthase, the main source of NO in the vasculature, and by enhancing removal of reactive oxygen species that are known to breakdown NO. Although acute dietary flavanol intake has been shown to augment skin blood flow, at least in part through increased NO, no studies have examined the impact of flavanol intake on skin perfusion during cold exposure. Improving skin blood flow to the extremities may enhance manual dexterity and reduce the risk of peripheral cold injury, benefits pertinent to warfighters or other populations that spend time in cold environments.
PURPOSE: To examine the effect of high-dose flavanol supplementation on CIVD. We hypothesized that acute and 8-day flavanol supplementation would augment CIVD during single-digit cold water immersion.
METHODS: Eleven healthy adults (24±6 yrs; 10M/1F) ingested cocoa-based flavanols (FLV; 900 mg/d) or caffeine and theobromine-matched placebo (PLA) for 8 days in a double-blind, randomized, crossover design. On Days 1 and 8, CIVD was assessed 2 hours after treatment ingestion. Subjects immersed their middle finger in warm water (42°C) for 15 minutes before cold water immersion (4°C) for 30 min, during which nail bed and finger pad skin temperature were measured continuously.
RESULTS: Flavanol ingestion had no effect (all P > 0.05) on CIVD event frequency (Day 1, FLV: 3±2 vs. PLA: 3±2; Day 8, FLV: 3±2 vs. PLA: 3±1) or amplitude (Day 1, FLV: 4.3±1.7 vs. PLA: 4.9±2.6 °C; Day 8, FLV: 3.9±1.9 vs. PLA: 3.9±2.0 °C) in the finger pad following acute or 8-day supplementation. Furthermore, average (Day 1, FLV: 9.2±1.5 vs. PLA: 9.2±1.8 °C; Day 8, FLV: 8.3±1.7 vs. PLA: 8.9±1.9 °C), maximum (Day 1, FLV: 11.9±3.0 vs. PLA: 11.2±2.3 °C; Day 8, FLV: 10.1±1.9 vs. PLA: 10.6±2.3 °C), and minimum (Day 1, FLV: 6.2±1.3 vs. PLA: 6.0±1.5 °C; Day 8, FLV: 5.8±1.8 vs. PLA: 6.2±1.7 °C) finger pad temperatures during cold water immersion were not different (all P > 0.05) between treatments on Day 1 or Day 8 of supplementation. Similarly, no differences (all P > 0.05) in CIVD parameters were observed in the nail bed following acute or 8-day supplementation.
CONCLUSION: Dietary ingestion of cocoa-based flavanols does not improve the CIVD response to single-digit cold water immersion.
PMID:35560310 | DOI:10.1096/fasebj.2022.36.S1.R3395