THE EFFECT OF VITAMIN C INTAKE ON GLYCOHEMOGLOBIN MEASUREMENTS

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THE EFFECT OF VITAMIN C INTAKE ON GLYCOHEMOGLOBIN MEASUREMENTS

Several studies have shown that vitamin C affects on hemoglobin glycation of proteins. However, the effects on hemoglobin glycation may be interpreted differently depending on the method used to measure glycohemoglobin. Six non-diabetic subjects received daily Vitamin C supplementation (500mg Bid) for three months. Fasting blood glucose, plasma vitamin C, HbA1c by ion-exchange HPLC, HbA1c by immunoassay, and total GHB by Affinity HPLC were measured at baseline, and monthly there after for 5 months. Results showed that fasting blood glucose did not change significantly throughout the study. Plasma vitamin C levels increased by 40% (P < 0. 01) by month 1, remained constant during the period of vitamin C intake, then returned to baseline level 2 months after stopping vitamin C supplementation. GHB measured by Affinity HPLC and HbA1c by immunoassay decreased significantly by month 2, remained lower at month 3 and returned to baseline within 2 month of discontinuing vitamin C. HbA1c measured by ion-exchange HPLC, however,was significantly increased within one month of taking vitamin C and remained increased during the period of vitamin C intake. Within 1 month after cessation of vitamin C,ion-exchange HbA1c values. dropped back to baseline levels.We conclude that vitamin C intake causes inhibition of hemoglobin glycation but that the methodology used for GHB measurement may effect interpretation of results. Vitamin C intake interferes directly with measurement of HbA1c by an ion-exchange method falsely increasing results relative to the true amount of GHB, which decreases. However,it should be kept in mind that because of the inhibition of glycation,the actual relationship between GHB and aver age glucose may be altered slightly by Vitamin C intake regardless of the method used.