BLOOD SUGAR LEVELS AND CARBOHYDRATE ADMINISTRATION IN HUMAN SUBJECTS DURING PROLONGED EXPOSURES TO MODERATELY LOW ALTITUDES

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Abstract
No significant change from the ground level condition occurred in the blood sugar level of 6 resting individuals fed a standard breakfast and then exposed to simulated altitudes of 8,000 and 10,000 ft. for 10 hr. periods without supplementary O2 and without food. Ingestion of glucose (70-150 gs.) at the midpoint of the exposure period induced secondary hypoglycemic reactions in the majority of subjects appr. 50% of the times tested. The hypoglycemic episodes usually began 3-5 hrs. after ingestion of the sugar sol., occurred with equal frequency and severity at altitude and ground level, and were characterized by sensations of nervousness, paresthesia, hunger, weakness, and, in the severe cases, by manifestations of pallor, sweating, and tremulousness, as well. Carbohydrate tolerance as measured by the time required for the blood sugar level to attain the pre-ingestion value was not appreciably altered at the altitudes studied. A comparison of sugar values obtained directly during the seizures, however, revealed the hypoglycemic component ("dip" below the base line) of the tolerance curve to be shortened at altitude, suggesting, thus, that the homeostatic mechanism controlling the blood sugar level may be affected at moderately low altitudes. The author deems the occurrence of adverse hypoglycemic reactions at altitude sufficiently hazardous to negate any gain in "ceiling" which may possibly result from high carbohydrate admin, under these conditions.