This study will investigate the effects of ketone ester drinks on cognitive performance in hypoxia.

In the setting of altitude-induced hypoxia, cognitive capacity degrades and can compromise both individual and team performance. This degradation is linked to falling brain energy (ATP) levels and an increased reliance on anaerobic energy production from glucose. Ketone bodies are the evolutionary alternative substrate to glucose for brain metabolic requirements; previous studies have shown that the presence of elevated ketone bodies (ketosis) maintains brain ATP levels and reduce cerebral anaerobic glycolysis during hypoxia. Ketosis can be achieved when fasting or following a ketogenic diet; however, these approaches are impractical. Exogenous ketone ester supplementation allows for rapid (< 30 mins) and significant elevation of blood ketone levels without the need to maintain a diet or fast.

HVMN, in collaboration with researchers at IHMC, proposes a study to investigate the effects of consuming an FDA-approved ketone ester 'food' on cognitive performance in the setting of hypoxia. For the proposed 4-arm within-subject study, participants will complete a cognitive performance test battery under the conditions of normoxia and then hypoxia following consumption of a ketone ester drink or a placebo drink (N.B for each study drink cognitive performance in both hypoxia and normoxia will be assessed in ONE visit):

VISIT A:

Arm1: Normoxia + Placebo Arm 2: Hypoxia + Placebo

VISIT B:

Arm 3: Normoxia + Ketone ester Arm 4: Hypoxia + Ketone ester

The investigators hypothesize that ketone ester supplementation will attenuate hypoxia-induced deterioration of operator cognitive performance.

Inclusion Criteria:

* Pass medical examination on enrollment.

Exclusion Criteria:

* Active smoker, substance abuse.

Study drinks will be matched for taste and appearance. Investigator preparing and administering the drink will not carry out the testing.