High Altitude Eating
If you’re participating in high altitude activities, there’s a real risk of malnutrition — living and exercising at altitude can lead to loss of body weight and muscle. This effect is more marked the higher you go, and the longer you spend in the reduced-oxygen environment. For example, there have been reports of weight losses of 3 per cent in eight days at 4,300m and up to 15 per cent after three months at 5,300 to 8,000m. Also, there are short-term problems of acclimatization to tackle. You need to know how to adjust your diet to minimize these problems. The key requirements are an increased calorie and fluid intake, and eating foods with a high carbohydrate content.
Don’t neglect fluids
Extra fluid intake continues to be crucially important. The higher the altitude the lower the humidity and the quicker sweat evaporates from the skin. This can lead you to think that you’re sweating less than usual — whatever you do, don’ t drink less than usual! Although your body will adapt to an extent after a while at altitude (eg, there’ s a decrease in the water vapour content of air breathed out), there will still be a net increase in fluid requirements. It’s also a good idea to cut down on caffeine and alcohol, as both are diuretics, encouraging loss of fluid.
Heavier reliance on carbs
Wherever you are, as an active athlete, you boost your capacity for endurance by eating a high-carb diet. But this becomes even more critical if you soar to high altitude. During both short and long-term altitude exposure, there is a decrease in the use of fat as an energy source, together with an increased reliance on carbohydrate. It’s thought that this shift makes it easier for oxygen to dissolve into the blood. Thus, there’ s a need for an even higher carbohydrate intake than usual. At altitudes over 5,OOO metres, experts have recommended that carbohydrate foods should be increased to as much as 70 per cent of total energy intake. A number of researchers have found that people spontaneously increase their carbohydrate consumption when at high elevations.
Muscle maintenance
Mountain climbers have been observed to lose 15 per cent of their thigh muscle cross sectional area after spending two months at altitudes greater than 5,500m. However, the same effects have not been seen at intermediate altitudes (2–3,000 metres).
Acute low oxygen depresses the rate at which muscle protein is made, and may increase the rate of protein breakdown. It’s thought that for altitudes lower than 5,000 metres, making sure that you’re getting enough calories will protect your muscles from actually decreasing in mass. When the body is strapped for calories it turns to breaking down muscle to provide extra energy.
Key points
1. Load up on carbohydrate foods before you leave, and continue to prioritize them when you’re at higher altitude.
2. Drier air means you’re at more risk of dehydration at high altitude. Drink more!
3. Your body will need more calories than normal. Add on extra carbohydrate foods and snacks.
4. Eat smaller, more frequent meals.
5. You’ll burn more carbohydrate than usual. Eat more starchy and sweet foods.
6. Vitamin E and branch-chain amino acid supplements may be helpful.
