Effect of acute zinc deprivation on plasma zinc and platelet aggregation in adult males

In view of earlier results obtained with rodents, the present study was designed to investigate the effect of acute zinc deprivation in man on plasma zinc concentration and the response of platelets to aggregating agents. Three adult men consumed a formula diet based largely on soybean protein for 12 to 14 days. During the control period the diet was supplemented with 12 mg zinc per day. Without supplementation the diet supplied approximately 0.5 mg zinc per 3.0 Mcal; it contained 0.7 ppm zinc, and 0.2% phytate. After removal of the zinc supplement plasma zinc dropped rapidly and reached a minimum by the 5th day. There was a wide diurnal variation in plasma zinc concentration in one subject with the overnight fasting value being the highest and decreasing soon after the morning meal. Platelet aggregation in response to ADP and arachidonate was impaired when plasma zinc was 60 µ g/dl or less and was restored to normal within 19 h of oral zinc supplementation. These results demonstrate that plasma zinc can be rapidly decreased by dietary zinc deprivation and that extracellular zinc plays an important role in platelet aggregation.