Role of sugars in human neutrophilic phagocytosis.

This study was designed to test a) whether carbohydrates other than glucose decreased the phagocytic capacity of neutrophils in normal human subjects, b) the duration of this effect, and c) the effect of fasting on neutrophihic phagocytosis. Venous blood was drawn from the arm after an overnight fast and at 0.5, 1, 2, 3, or 5 hr postprandial and this was incubated with a suspension of Staphylococcus epidermidis. The phagocytic index (mean number of bacteria viewed within each neutrophil) was determined by microscopic examination of slides prepared with Wright’s stain. Oral lOOi portions of carbohydrate from glucose, fructose, sucrose, honey, or orange juice all significantly decreased the capacity of neutrophils to engulf bacteria as measured by the slide technique. Starch ingestion did not have this effect. The decrease in phagocytic index was rapid following the ingestion of simple carbohydrates. The greatest effects occurred between 1 and 2 hr postprandial, but the values were still significantly below the fasting control values 5 hr after feeding (P < 0.00 1). The decreased phagocytic index was not significantly associated with the number of neutrophils. These data suggest that the function and not the number of phagocytes was altered by ingestion of sugars. This implicates glucose and other simple carbohydrates in the control of phagocytosis and shows that the effects last for at least 5 hr. On the other hand, a fast of 36 or 60 hr significantly increased (P < 0.001) the phagocytic index. Am. J. Clin. Nutr. 26: 1180-1184, 1973. A major defense mechanism of higher animals is neutrophilic phagocytosis (1, 2). Phagocytosis is an energy requiring mechanism that is inhibited by an inadequate supply of glucose (3). On the other hand, there is evidence to suggest that an excess of glucose may also decrease phagocytic activity. Patients with diabetes mellitus are characterized by elevated blood glucose levels and lowered resistance to infection. Diabetics have also been found to have impaired neutrophilic phagocytosis as compared with normal subjects (4-7). Kijak et al. (8) found that the greater the blood glucose level the lower the phagocytic capacity in diabetic patients. Moreover, oral administration of increasing amounts of glucose progressively lowered the phagocytic capacity of neutrophils in normal subjects (8) or patients (9) when measured at 45 mm postprandial. Thus, both the ingestion of glucose and the level of glucose in the blood seem to be implicated in the control of neutrophilic phagocytosis. There seems to be no further information relating carbohydrates with neutrophilic phagocytosis or with the duration of decreased phagocytosis following glucose ingestion. The purpose of these studies was to a) test whether ingestion of carbohydrates other than glucose decreases neutrophilic phagocytosis, b) determine how long neutrophilic phagocytosis remains lowered after oral administration of carbohydrate, and c) test whether fasting (the absence of oral glucose sources) affects neutrophilic phagocytosis.