The Variations in the Content of Sugar in the Blood

Alimentary glycosuria, as exhibited in the renal excretion of sugar when undue amounts of carbohydrates are ingested by persons who fail to manifest this symptom under ordinary conditions of diet, has long been recognized and investigated. The prominence which the clinical estimation of the sugar-content of the blood has assumed in recent months, and the diagnostic importance which has been attached to the variations in this blood-constant as a possible index of incipient metabolic disorder, have seemed to call for a careful determination of the precise effect which the ingestion of carbohydrate may exert in altering the quantum of blood-sugar under well controlled conditions in otherwise healthy persons. The determination of normal values and physiologic deviations from them is always essential as the rational beginning in the establishment of a new scheme of diagnostic procedure. Such an undertaking has lately been carried out in the medical clinic of the University of Copenhagen by Dr. Jacobsen. Estimations were made after comparatively brief successive intervals in the same persons who had taken various substances in suitable quantities three or four hours after breakfast. It is well known that healthy persons frequently exhibit glycosuria after the ingestion of from 150 to 200 gm. of dextrose under similar conditions — and this is usually taken as an index of alimentary glycosuria. In contrast with some earlier studies the Danish investigator has observed an unmistakable hyperglycemia in every instance after ingestion of 100 gm. of dextrose; in some instances glycosuria likewise appeared simultaneously. In view of this fact, Jacobsen points out that a mild transient glycosuria under such circumstances is no longer to be looked on as a diabetic symptom. 

Comparable quantities of starch administered in the form of bread likewise led to hyperglycemia. The increase in the percentage of sugar was quite as pronounced, in some cases, as that which occurred after the introduction of glucose; but the onset of the hyperglycemia was slower, as might be expected, in view of the slower liberation of sugar by the digestive processes. Fat or protein, in contrast with glucose or starch, were without effect on the level of tbe sugar in the blood ; but when starch was administered along with fat the degree of the alimentary hyperglycemia was relatively mild. The explanation of the inhibitory effect of the fat on the tendency to hyperglycemia is presumably to be sought either in the fact that the presence of the fat mechanically interferes with the ready digestion of starch and consequent liberation and absorption of sugar, or that fat retards the discharge of contents from the stomach and delays absorption in this way. 

Effects of a similar sort were observed also in the blood of diabetics fed as indicated before. There is a tendency, however, for a greater increase in the bloodsugar content to assert itself in the abnormal than in the normal persons after an identical intake of carbohydrate; and the same increment of blood-sugar in diabetics is far more likely to lead to glycosuria. In healthy persons, for example, the content of blood-sugar may be raised to 0.16 or 0.17 per cent., without inducing an elimination of glucose. In diabetics the consequences are exaggerated in every direction. The possession of these newer data will serve to orient us better in the direction of successful diagnosis on the' basis of the information to be obtained for the estimation of the sugar-content of the blood under known or controlled conditions of diet.

1. Jacobsen, A. T. B.: Untersuchungen Uber den Einfluss verschiedener Nahrungsmittel auf den Blutzucker bei normalen, zuckerkranken und graviden Personen, Biochem. Ztschr., 1913, lxvi, 471.