Meeting Energy and Nutrient Needs

Energy expenditures of humans climbing Mount Everest average 2.5 to 3.0 times higher than at sea level.²⁷ It is easy to understand why weight loss from reduced energy intake is a common outcome of exercise in cold or high-altitude environments.²⁸ Athletes performing in these environments should make a conscious effort to eat at frequent intervals. They should focus on carbohydrate foods because these foods take less oxygen to metabolize than do fat or protein foods, help replace glycogen stores, and have a protein-sparing effect. In addition, inadequate carbohydrate consumption will eventually result in low blood sugar, which leads to mental confusion and disorientation. Some reports indicate that mountaineers show a preference for carbohydrates and an aversion to fat.²⁹ However, this finding is not consistent; other studies indicate that athletes at high altitude do not shift their food selections away from high-fat items and toward high-carbohydrate foods.³⁰ The same report indicates that high-altitude environments blunt the sense of taste, which may contribute to inadequate energy intake. This inadequate energy intake leads to a weight loss (including muscle weight) that negatively affects strength, endurance, and the capacity to produce heat. The goal should therefore be to consume an adequate volume of food to provide sufficient calories rather than place undo importance on the distribution of energy substrates. Athletes should have foods available to them that they know they will eat in large quantities and that make them feel good after they are consumed. To make matters even more difficult, the time to cook a meal doubles for each 5,000-feet (1,500 meter) climb in elevation. Prepackaged, high-carbohydrate snacks and foods are a good alternative for most meals, with cooked meals reserved for those times when athletes have available water and time.

The intake of vitamins and minerals is something better considered before exposure to either cold or high altitude. Iron status in particular should be excellent before attempting a high-altitude trek because oxygen-carrying capacity is stretched to its limit in this environment. Taking iron supplements while on the climb is not likely to be of much benefit because it takes a great deal of time (months) to improve a poor iron status. Oxidative stress may be higher in hot and cold environments, so consumption of foods that contain antioxidants or periodic consumption of a multivitamin and multimineral supplement should be considered.³¹ A study of oxidative stress in humans at high altitude found that those receiving an antioxidant mixture had lower breath pentane (a marker of oxidative stress) compared with those receiving single antioxidant supplements. Consuming a variety of antioxidants, such as ascorbic acid, beta-carotene, selenium, and vitamin E (as would be present in a broad-spectrum supplement), is therefore likely a better strategy than focusing on a single antioxidant.³²