Altitude tolerance in rats in relation to carbohydrates and fats in their diet.

Rats were exposed to simulated altitudes of 3658, 4877 and 7620 m, 5 h/d for 30 d, at ambient temperature of 28 degrees C. Voluntary food intake, growth rate, and survival time were measured under effects of commercial diet (50% CHO, 4% fat and 24% protein), high fat diet (52% fat), and high carbohydrate diet (75% CHO). The results showed that altitude-exposed rats on high CHO diet had improved growth rate, but lowered survival time on their subsequent exposure (at the end of a 1-month period) to severe hypoxia (5% oxygen). The animals on high fat diet had very poor growth rate, as they ate very little amount of it voluntarily, either at sea level or under high-altitude conditions. These rats, however, had tremendously increased resistance to severe hypoxia (survival time greater than 60 min as compared with greater than 12 mins of those on commercial or high CHO diet).