Overcoming altitude with antioxidants - by Lauren Bernicchi

The 1968 Mexico Olympics sparked awareness of how altitude training can influence athletic performance. Since then, athletes often use altitude training to improve their competitive performance, both at altitude and sea-level.

Elite athletes typically train at moderate altitudes between 1600-2400m, while mountaineers and military groups are more likely to train at higher altitudes. 

So how does it work? Altitude training at hypoxic (low oxygen) levels is an environmental stressor that can cause particular physiological changes and positively influence an athlete’s exercise capacity and endurance. Athletes undergo a hyperventilation response, which delivers more oxygen to tissues by increasing the rate and depth of breathing. The classic short-term physiological responses to altitude are increased haemoglobin concentrations and dilation of blood vessels (to increase the oxygen delivered to tissues). It is this raised haemoglobin that could potentially give an athlete that extra oomph needed for victory. Although these changes seem great for athletic performance, hypoxic conditions of moderate altitude can also challenge an athlete’s body and potentially reduce muscular function (1).

Training at altitude is also linked with increased production of free radical oxygen species (ROS), and when antioxidant levels are too low, this can lead to oxidative stress. Oxidative stress initiates the positive adaptive response to hypoxia and up-regulates an athlete’s antioxidant defences. Although this is necessary for an athlete’s response to stress, overproduction of ROS can cause damage to lipids, proteins and DNA, which can harm cell and immune function, compromising the body’s ability to detoxify or repair itself.

It is unclear, however, whether altitude-induced oxidative stress affects athletes apart from potentially causing acute mountain sickness at high altitude. Some studies show that oxidative stress is linked to inflammation and illness, yet other studies have disputed this. Although it makes sense to assume there is an increased likelihood of illness at moderate altitude, there is limited evidence to prove this. A particular review found that there is no evidence that altitude training threatens immunity, while other recent evidence suggests that it may even enhance an athlete’s health status (2). 

More and more people are beginning to understand the link between stress and inflammation, which as we know, is linked to all areas of health. Too much of anything isn’t good for anyone, so why risk an athlete’s health and performance when it comes to too much oxidative stress? Find the balance between ROS and antioxidants.

fruitvegSo, are antioxidant supplements necessary? Antioxidants from foods or supplements can neutralise ROS. Because of this, it is logical to think that antioxidant supplementation might work as an intervention to neutralise any altitude-induced oxidative stress in athletes. Recently, however, studies have found either no effect or mixed results. Another thought is that by dampening ROS, antioxidant supplementation may reduce adaptive responses to altitude training and be counterproductive for athletes. Thus, for supplementing with antioxidants, more may not always be better. Currently, there is insufficient evidence for using high-dose single antioxidant supplementation to reduce or remove altitude-induced oxidative stress, but there is promising evidence for the use of food-based antioxidants. The safest proven method to combat oxidative stress and its potential dangers is to incorporate large amounts of antioxidant-rich foods into the daily diet of altitude-training athletes; i.e. a diet filled with ample fruits and vegetables. This should include vitamin C to increase the bioavailability of an athlete’s iron.

beetrootBesides this consideration, specific foods can help reduce the effects of hypoxia and provide antioxidant support. Have you heard of nitrates? Dietary nitrate supplementation (NO3) is emerging as a potential dietary aid for individuals training in hypoxia (3). Nitric oxide (NO) is a regulator of altitude-induced physiological and adaptive processes. Nitrates can increase the release of NO into vascular smooth muscle cells and cause muscle relaxation and vasodilation. This makes the delivery of oxygen to tissues faster and easier, and can increase the uptake of oxygen by the active muscles. Nitrates are present in many food sources, including beetroot, garlic, leafy greens, pomegranates, and dark chocolate. Recent studies show that NO3, commonly consumed in beetroot juice or powder, can reduce the oxygen cost of submaximal exercise, and improve muscle efficiency and exercise performance (4). However, recent hypoxia-based studies on elite endurance athletes show inconsistencies, with only some athletes benefiting from nitrate supplementation.

Altitude training has proven to be an effective way to improve an athlete’s performance at altitude or sea-level. While I believe the evidence for antioxidant and nitrate supplementation is promising, it is not yet robust enough to fully support it. Until the evidence says otherwise, the best way for an athlete to improve their performance and combat altitude-induced oxidative stress is to consume a diet full of colourful and varied vegetables and fruits, and nitrate food sources.

References:

  1. Michalczyk et al (2016). Dietary recommendations for cyclists during altitude training. Nutrients. 8(6):377.
  2. Stellingwerff T et al (2019). Nutrition and altitude: strategies to enhance adaptation, improve performance and maintain health: A narrative review. Sports Medicine.
  3. Cumpstey A et al (2017). Effects of dietary nitrate on respiratory physiology at high altitude – Results from the Xtreme Alps study. Nitric Oxide. 71:57-68.
  4. Shannon O et al (2017). “Beet-ing” the mountain: A review of the physiological and performance effects of dietary nitrate supplementation at simulated and terrestrial altitude. Sports Medicine. 47(11):2155-2169.