Search

Background: Ascorbate and glutathione play central roles in the defense against free radicals and oxidants that are implicated in chronic diseases. Objective: The objective was to determine the ability of vitamin C supplements to modulate the concentration of glutathione in human lymphocytes. Design: The effect of vitamin C supplements was determined in a sequential study with time points before supplementation, after 13 wk of vitamin C supplements (500 or 1000 mg/d), and after 13 wk of matching placebo. The supplementation group was selected on the basis of low plasma ascorbate (< 33 mmol/L) and consisted of 48 healthy men and women, smokers and nonsmokers, aged 25-64 y. Ascorbate and glutathione were measured in purified lymphocytes. Results: At baseline, the mean ([+ or -] SD) concentration of plasma ascorbate was 19.5 [+ or -] 7.2 [micro]mol/L, 22.5 [micro]mol/L below the median of normal distribution. The ascorbate concentration in plasma was linearly associated with that in lymphocytes (r = 0.53, P < 0.001). On supplementation with vitamin C, lymphocyte ascorbate increased by 51% (from 16.7 [+ or -] 4.9 to 25.3 [+ or -] 6.9 nmol/mg protein; P < 0.001) and was accompanied by an increase of lymphocyte glutathione by 18% (from 22.5 [+ or -] 4.5 to 26.6 [+ or -] 6.5 nmol/mg protein; P < 0.001). After placebo, the ascorbate and glutathione concentrations fell to near baseline concentrations (17.1 [+ or -] 5.4 and 23.5 [+ or -] 6.4 nmol/mg protein, respectively). No significant interaction was observed for sex and smoking status. Finally, the changes in lymphocyte ascorbate after supplementation were strongly associated with changes in lymphocyte glutathione (r = 0.71, P < 0.001). The association suggests that every 1-mol change in ascorbate is accompanied by a change of [approximately equal to] 0.5 mol in glutathione. Conclusion: Vitamin C supplements increase glutathione in human lymphocytes.

Background: Endogenous reactive oxygen species appear to contribute to aging and cancer and dietary antioxidants, present in fruit and vegetables, counteract these effects. Objective: The objective was to examine the association between intracellular glutathione, ascorbate (vitamin C), and [Alpha]-tocopherol (vitamin E) in human lymphocytes. Design: The study group consisted of 240 healthy nonsmoking volunteers with an approximately equal number of male and female subjects subdivided into 3 age groups: 18-39, 40-59, and [is greater than or equal to] 60 y). Glutathione, glutathione disulfide, ascorbate, and [Alpha]-tocopherol were measured in lymphocytes by HPLC. Results: The average concentration of antioxidants in lymphocytes was 27 [+ or -] 8 nmol/mg protein for glutathione, 21 [+ or -] 8 nmol/mg protein for ascorbate, and 0.4 [+ or -] 0.2 nmol/mg protein for [Alpha]-tocopherol. There was a strong positive correlation between glutathione and ascorbate (r = 0.62, P [is less than] 0.001). No correlation was observed for glutathione and ascorbate with [Alpha]-tocopherol. The concentration of glutathione in lymphocytes was inversely correlated with age (r = - 0.19, P [is less than] 0.01), as was that of ascorbate (r = - 0.22, P [is less than] 0.01), with 10-20% lower values in elderly than in young and elderly subjects. The concentrations of glutathione in lymphocytes were as much as 25% higher and those of ascorbate were as much as 38% higher during the summer than during the winter. The seasonal variation of ascorbate in lymphocytes was described by a linear function for age and a periodic sine function for season. Conclusion: Glutathione and ascorbate are directly correlated in human lymphocytes. Am J Clin Nutr 2000;71:1194-200. KEY WORDS Vitamin C, vitamin E, glutathione, lymphocytes, ascorbic acid, antioxidants, micronutrients, aging, elderly, cancer, reactive oxygen species, season