Cocoa-rich Bioflavanol Supplementation Effects During Cold Exposure

The primary purpose is to test whether cocoa-rich bioflavanols can improve blood flow to the hand and fingers and improve hand function/dexterity during cold exposure. Secondary purpose is to understand whether bioflavanol supplementation can change the gut microbiome.

Loss of manual dexterity significantly impacts Warfighter effectiveness and lethality on the cold-weather battlefield. Identifying countermeasures that improve hand and finger temperatures, hand and finger blood flow, manual dexterity, and thermal comfort may lead to better Warfighter performance. A primary purpose of this study is to test the efficacy of a commercial off-the-shelf cocoa-rich bioflavanol product on hand/finger blood flow and temperature, manual dexterity, and thermal comfort during whole-body cold exposure. Another primary purpose is to determine the effect of bioflavanols on the finger cold-induced vasodilation (CIVD) response to cold-water immersion. Secondary purposes are to determine if: a) cocoa-rich flavanols stimulate the growth of beneficial gut bacteria and b) impact attention and effort perception during dexterity task completion in the cold. Two experimental studies (n = 20 in each study, 10 women and 10 men, 18-49 yr) will be conducted. Experiment #1 consists of immersing the middle finger in cold water (4°C) for 30 minutes; experiment #2 consists of whole-body cold exposure (8°C air, 90-min exposure, wearing cold-weather clothing but bare-handed). In both experiments, outcomes will be measured after both acute flavanol or placebo ingestion and chronic ingestion of flavanol/placebo (8 days of supplementation). Daily flavanol ingestion will be 900 mg/day. Volunteers will serve as their own controls in this crossover, double-blind research design. The washout period between flavanol and placebo treatments will be at least 2 weeks (longer for women who will be tested only during the follicular phase). Measurements during these tests include skin temperature, skin blood flow, fine and gross motor dexterity, thermal comfort, and effort perception. Fecal samples, in both experiments, will be collected before and after 8 days of cocoa-rich bioflavanol supplementation to examine if bioflavanol supplementation increases the number of beneficial bacteria in the gut microbiome. Information from this study will inform combat nutrition developers about the efficacy of cocoa-rich bioflavanols and possible inclusion into cold-weather field rations.