Nutrition at Altitude

Key Points

1. To optimise the physiological and performance benefits of altitude training, nutrition must be addressed due to: increased energy requirements required for training, increased sweating and urination leading to increased water losses and secondary effects such as altitude induced suppression of appetite.

2. Monitor hydration status by recording pre and post training session weight. Rehydration to the pre training session weight will help athletes stay on top of their individual fluid needs.

3. A high carbohydrate diet (7-10g/kg body weight/day) is recommended for athletes exercising intensively, which should be further increased when exposed to simulated altitude (12-13g/kg body weight/day). This diet alone should contain sufficient amounts of all anti-oxidants required. Antioxidant supplementation should only be considered when natural foods such as fruit and vegetables are not available.

4. Increased red blood cell formation requires an increased availability of iron – therefore iron supplementation (up to 100mg/day) is recommended.

5. Vitamin D supplementation (up to 1mg/day – equivalent to 1000mcg/day or 4000 IU/day) is also recommended.

Altitude Training: Nutritional Advice

The importance of nutrition to competitive performance is well known and practised by athletes, across all sports. However, due to the specific effects that chronic exposure to a low oxygen environment has upon your physiology and metabolism, this blog post is focused upon the most important aspects of a nutrition strategy for altitude training, including both proper hydration and optimal energy balance.¹ Key nutritional areas addressed: changes in body composition, hydration, dietary carbohydrate intake recommendations, iron storage, vitamin D and anti-oxidants.

Body composition during altitude training

During the initial stages of altitude exposure, respiratory rate and urinary water loss increases, leading to a slight reduction in total body mass.¹ Allowing chronic exposure, leads to true physiological changes, most prominently loss of body mass, protein stores² and fat content.^{3, 4} This is a consequence of an increase in basal metabolic rate,⁵ a relative increase in training loads⁶ and suppressed appetite leading to a decreased calorie intake unless consciously addressed.

Hydration during altitude training

The maintenance of proper fluid balance during training and competition is a key factor that determines sport performance. Traditionally this has been extremely challenging for athletes training at altitude in both hot and humid environments.¹ With the development of simulated altitude, this has allowed athletes to train in their home environments, overcoming the difficulties that these particular climates present.

Within the first few days at altitude, there is a tendency toward dehydration due to increased respiratory water loss by enhanced ventilation⁷, and increased urinary water loss secondary to downregulation of the renin-angiotensin-aldosterone hormone mechanism.⁸ This may increase urinary water loss up to 500ml per day.⁹ Monitoring weight before and after training sessions allows an accurate replenishment of fluid loss (urine osmolality can be used alongside this as a gold standard of monitoring hydration status). This is important not only to avoid dehydration, but also being careful not to overhydrate, as this may hinder the adaptive processes to altitude and decrease performance. Athletes and coaches must also take into consideration the fact that diuretic drinks like coffee, tea and certain energy drinks with caffeine, can increase the diuretic effect but on the other hand can help increase the intensity of exercise and reduce the perception of fatigue.¹

Dietary carbohydrate intake recommendations

Athletes training or competing at high altitude dramatically increase the rate of energy expenditure compared to normoxia.¹⁰ It is well known that the higher the exercise intensity, the greater the amount of carbohydrates used as fuel for working muscles. Adequate carbohydrate consumption before exercise increases glycogen stores in the muscle and liver, minimising low blood sugars and central fatigue.¹¹ Sufficient carbohydrate consumption after training or competition provides quick glycogen resynthesis, reduced muscle soreness and enhanced muscle recovery.¹²

The carbohydrate intake recommendation for endurance trained athletes ranges from 7-10g/kg of body mass per day,¹³ which should increase to 12-13kg/day when utilising altitude training.¹⁴

It is critical for athletes to consume different kinds of carbohydrates. During and immediately after exercise, carbohydrate products with a high glycaemic index should be preferred. They can include glucose or disaccharides derived from both liquid and solid foods, like sport drinks and fruit bars.¹⁵ On the other hand, during main meals, athletes should consume rather complex low glycaemic carbohydrates, derived from solid foods like cereals and grains, breads, vegetables, fruits and legumes.¹⁵

Iron Storage

Iron status in particular should be at a high level before attempting altitude training. In addition to the previously mentioned role of iron in the production of red blood cells, it plays an important role in the antioxidant defence not only as an antioxidant microelement but also because appropriate supply of oxygen to the working muscles depends indirectly on the level of iron.¹⁶

As a result of acclimatisation to altitude due to an increase in erythropoiesis, a decline in iron storage in the blood is observed.¹⁷ In studies, a significant reduction in the concentration of ferritin in the blood at altitudes above 2000m was observed.^{17, 18} Low levels of ferritin and iron in the blood can impair the increase in haemoglobin concentration in athletes exposed to hypoxia. In many studies investigating athletes during altitude training, supplementation with up to 100mg of iron a day was used to prevent potential anaemia from occurring (consumption of Spatone liquid iron sachets can be particularly useful to facilitate this – apple flavoured sachets can help reduce the distinctive taste of iron).

The best natural sources of iron are red meats like beef, offal and seafood. Vegetarian athletes should consume higher amounts of soya beans, beans, and green vegetables like parsley, broccoli and sprouts to provide appropriate amounts of iron. Unfortunately, the iron of those products is poorly absorbed due to significant contents of fibre. Grains, seeds and nuts are a very good source of other minerals mentioned above.

Vitamin D

The identification of the vitamin D receptor in the heart and blood vessels raised a possibility of potential cardiovascular effects of vitamin D,^{19, 20} and thereby most likely on aerobic exercise, which is known to induce cardiovascular changes associated with marked increases of aerobic power and endurance performance.²¹

Findings confirming the high prevalence of vitamin D deficiency in the general population, as well as in athletes,²² and a significant decrease of serum vitamin D level in alpinists after their return from mountaineering expeditions (14 days, 3200–3616m above sea level)²³ suggests that vitamin D supplementation should be considered in athletes who stay at high altitude.

It is recommended to supplement athletes training at altitude with up to 1mg/day (equivalent to 1000mcg/day or 4000 IU/day) of vitamin D, especially in the winter months of the year.

Antioxidants

A well balanced diet full of natural antioxidants can minimize the level of oxidative stress produced during high volume and high intensity training.²⁴ While training at altitude, athletes should consume high amounts of different kinds of fruit like blueberry, acai berry, goy berry, red grapes, raspberry, orange, papaya, blackcurrant, cherry, kiwi, strawberry, red grapes, mango, melon, grapefruit and lemon.^{25, 26} Those fruits are rich in naturally occurring vitamin C, carotenes, polyphenols and many other phytochemicals.^{27, 28}

A cyclist’s diet should also contain large amounts of vegetables, especially tomatoes, carrots, spinach, beetroot, broccoli, parsley, avocado, which are naturally full of antioxidants, such as vitamin A, vitamin C, carotenes and glutathione.^{27, 29, 30}

References

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20. Merke J, Hofmann W, Goldschmidt D. Demonstration of 1,25(OH) 2 vitamin D3 receptors and actions in vascular smooth muscle cells in vitro. Calcified Tissue International. 1987; 41: 112–114.

21. Hellsten Y, Nyberg M. Cardiovascular adaptations to exercise training. Comprehensive Physiology. 2015; 6: 1–32.

22. Williams S, Heuberger R. Outcomes of vitamin D supplementation in adults who are deficient on critically III: A review of the literature. American Journal of Therapeutics. 2015; 23(6): e1890-e1902.

23. Kasprzak ZS, ́liwocka E, Henning K et al. Vitamin D, Iron metabolism, and diet in alpinists during a 2-week high-altitude climb. High Altitude Medicine and Biology. 2015; 16: 230–235.

24. Palazzetti S, Rousseau AS, Richard MJ et al. Antioxidant supplementation preserves antioxidant response in physical training and low antioxidant intake. British Journal of Nutrition. 2004; 91: 91–100.

25. McAnulty LS, Nieman DC, Dumke CL et al. Effects of blueberry ingestion on natural killer cell counts, oxidative stress, and inflammation prior to and after 2.5 h of running. Applied Physiology, Nutrition and Metabolism. 2011; 36: 976–984.

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28. Baur JA, Sinclair DA. Therapeutic potential of resveratrol: The invivo Nature Reviews Drug Discovery. 2006; 5: 493–506.

30. Nieman DC, Williams AS, Shanely RA et al. Quercetin’s influence on exercise performance and muscle mitochondrial biogenesis. Medicine and Science in Sports and Exercise. 2010; 42: 338–345.
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