Dietary requirements of subjects exposed to hyperbaric He-O2 conditions: effects of supplementation with major nutrient groups.

A 4-week growth study was conducted to determine whether changes in the type of diet could adequately compensate for the increased demands made upon the body by the stresses associated with exposure to hyperbaric He-O2 conditions. A normal rat diet (Hegsted-Chang) was used as a standard diet. This diet was also modified by increasing the fat content 25%, mineral mixture 25%, casein 50%, or all vitamins (including cod liver oil) 50%, or by decreasing the casein portion 10% from the standard levels. The corn starch portion was adjusted appropriately to maintain isocaloric properties of the various test diets. Male Sprague-Dawley rats served as the experimental subjects and were exposed to 1 ATA room air, 11 ATA He-O2, or 21 ATA He-O2 environmental conditions. The rats fed fat-supplemented diets grew as well under 11 ATA He-O2--but not under 21 ATA He-O2 conditions--as those fed the standard diet and exposed to 1 ATA room-air conditions. The rats fed protein-supplemented diets grew as well under both hyperbaric conditions as the control rats. Although the rat growth under the hyperbaric conditions equaled that under control conditions, it was less efficient because more food was required to produce each 1 g of gain. Significant differences were also observed in the apparent digestibilities of the various diets and in the protein, fat, and mineral contents of the carcasses.