Cocoa Flavanol Intake and Exercise in Hypoxia
Condition: Hypoxia, Altitude
MeSH terms: Altitude Sickness; Hypoxia
Study type: Interventional

Summary: 
      Not uncommonly, sports events take place or finish at high altitude, where physical and
      cognitive (e.g. decision-making, motor control) performance in hypoxia is determining the
      outcome of sports performance. With nutritional supplements growing in popularity in the
      athletic and non-athletic population, research is increasingly focussing on dietary
      constituents which can improve cognitive and exercise performance.

      Flavonoids, a subgroup of polyphenols, are a class of natural compounds found in the human
      diet and include subcategories of flavanols, flavonols, iso-flavones, flavones, and
      anthocyanidins. Intake of flavanols, found in grapes, tea, red wine, apples and especially
      cocoa, causes an nitric oxide (NO)-mediated vasodilatation and can improve peripheral and
      cerebral blood flow (CBF).

      For cocoa flavanol (CF), there is evidence that both long term and acute intake can improve
      cognitive function, with the quantity and bioavailability of the consumed CF highly
      influencing its beneficial effects and with higher doses eliciting greater effects on
      cognition. Increased CBF following acute and chronic (3 months) CF intake has been
      demonstrated in healthy young subjects. Moreover, cognitive performance and mood during
      sustained mental efforts are improved after acute CF intake in healthy subjects and CF intake
      can increase prefrontal oxygenation during cognitive tasks in well-trained athletes.
      Moreover, CF intake is not only associated with an improved blood flow, but it might also
      improve exercise performance following 2 weeks of dark chocolate intake. On top of that, CF
      is known to have anti-oxidant properties and 2 week CF intake has been associated with
      reduced oxidative-stress markers following exercise.

      In hypoxic conditions, arterial pressure of oxygen (PaO2) and arterial saturation of O2
      (SaO2) are decreased, compromising tissue oxygen delivery. Since brain function and brain
      integrity are dependent on continuous oxygen supply, brain desaturation may result in an
      impaired cognitive function in hypoxia. The severity of the impairment is related to the
      extent of high altitude, with at 3000m (=14.3 % oxygen (O2); = 71% of oxygen available at sea
      level) psychomotor impairments being visible. Cerebral oxygenation, which can be measured by
      Near-infrared spectroscopy, is lowered in hypoxia.

      It remains unclear whether CF intake can influence cerebral oxygenation and perfusion in
      hypoxic conditions and whether CF intake could (partially) counteract hypoxia-induced
      cognitive impairments. Therefore, the first aim of this study was to investigate whether
      cognitive function and prefrontal oxygenation during a mental demanding task will be impaired
      by hypoxic conditions (3000m altitude; 14.3% O2) and whether these impairments can be
      partially restored by subchronic CF intake (7 days, 900 mg/day).

      Hypoxia also impairs physical performance. Hypoxia-induced reductions in cerebral oxygenation
      may favour central fatigue, i.e. the failure of the central nervous system to excite the
      motoneurons adequately, hence impairing exercise performance in hypoxic conditions. Since
      hypoxia also impairs oxygen delivery to muscle tissue, the decreased oxygen supply to and
      impaired oxidative energy production in the exercising muscle is a second factor negatively
      affecting exercise performance.

      Besides the aforementioned effects of altitude on O2 delivery, hypoxia also results in
      increased oxidative stress. Oxidative stress refers to the imbalance between prooxidant and
      antioxidant levels in favor of prooxidants in cells and tissues and can result from
      diminished antioxidant levels or increased production of reactive oxygen species. The latter
      can be induced by both exhaustive exercise and high altitude. Since oxidative stress can be
      counteracted by CF, we also aim to investigate how markers of oxidative stress can be
      affected by CF intake by exercise in hypoxia. Therefore, the second aim of this study was to
      investigate possible beneficial effects of CF intake on changes in cerebral and muscle
      vasoreactivity and oxidative stress during exercise in hypoxia and its implications on
      exercise performance.
    


Intervention name(s): cocoa flavanol; placebo
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): 7 days intake of cocoa flavanol supplement (naturex); 7 days of placebo intake
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Other