Body weight and prior depletion affect plasma ascorbate levels attained onidentical vitamin C intake: A controlled-diet study

Purpose: To evaluate the role of factors that may affect the lever of plasm a ascorbic acid (AA), including age, body weight, physical activity, minor illness and the impact of prior depletion and repletion. Methods: After one month of stabilization on 60 me vitamin C/day, subjects underwent two complete depletion-repletion cycles (one cycle=one month of v itamin C depletion with nine mg/day, followed by one month of repletion wit h 117 mg per day). Subjects (68 men, ages 30 to 59 years) did not smoke or drink alcohol during the study. All food was provided by the study. Results: There was extreme individual variability in the plasma AA level ac hieved on an identical repletion dose: after four weeks at 117 mg/day of vi tamin C AA ranged from 26.5 mu mol/L to 85.8 mu mol/L. Body weight was inve rsely associated with plasma AA attained (p<0.0001). Regression analysis in dicated that, compared to a 130-lb man, a 200-lb man reached 10 mu mol/L ro wer AA after the first repletion and 18 mu mol/L lower AA after the second repletion. One-third of the subjects did not reach a plasma plateau after t he first repletion. Prier depletion and apparent repletion also had a major impact, and only 10% of subjects reached the same plasma AA on the second repletion as on the first repletion. Conclusions: Plasma AA attained on a given dose depends on body weight (or dose per kg of body weight) and an whether or not any prior depletions had been repleted adequately. The results have implications for nutrition recom mendations and research design.