The Biochemical, Physiological, and Metabolic Evaluation of Human Subjects in a Life Support Systems Evaluator and on a Liquid Food Diet

A 6-week study with 4 students as volunteer subjects was conducted to evaluate their water, caloric, and protein requirements under simulated stresses of aerospace. The subjects spent 28 days in the Life Support Systems Evaluator; 2 subjects wore the MA-10 space suit, unpressurized, for 8 hrs a day. They ate a 1-cycle, 4 meal per day, fresh food diet and a 1-cycle, 4 meal per day, liquid food diet. The only variety in the fresh food diet was the meat and fruit served at each meal. This diet was highly acceptable and did not show monotony even after 21 days. Flavors were the only variety in the liquid food diet: Cherry, vanilla, chocolate, and strawberry. This diet was unacceptable and monotonous, and less acceptable with time. The fresh food diet contained 81 g of protein, 164 g of fat, 166 g of carbohydrate, and 2329 k cal of energy. The liquid food diet contained 70 g of protein, 167 g of fat, 204 g of carbohydrate, and 2444 k cal of energy. The daily requirement of water was about 3300 ml on the fresh food diet and about 2500 ml on the liquid food diet. The liquid food diet was used less efficiently than the fresh food diet. Consequently, the subjects were in negative balance for calcium, potassium, and phosphorus although the concentrations of these elements in the diet were many times that found in the fresh food diet. The caloric value of the diet could support only a 65 kg man without weight loss. All the clinical data including heart rate, blood pressure, and oral temperature were in the normal range and no significant differences were observed due to confinement in the Life Support Systems Evaluator or due to wearing the unpressurized MA-10 space suit. (Author)