Plasma total glutathione in humans and its association with demographic and health-related factors

The tripeptide glutathione is proposed to be protective against a number of chronic diseases including cardiovascular disease and cancer. However, there have been few studies of plasma glutathione levels in humans and in those studies the numbers of participants have been very small. In an exploratory analysis the determinants of plasma total glutathione (GSH(t)) were investigated in a group of 100 volunteers aged 18-61 years in Atlanta, Georgia, USA during June and July 1989. Data on demographic and health-related factors were collected by interview and plasma GSH(t) was measured using a recently modified laboratory method. The mean concentration of plasma GSH(t) for all 100 participants was 761 micrograms/l, with a standard deviation of 451 micrograms/l, a range of 86-2889 micrograms/l and a median of 649 micrograms/l. Men had significantly higher levels of plasma GSH(t) than women (924 v. 692 micrograms/l; P = 0.006). Seventh-day Adventists participating in the present study had higher plasma GSH(t) levels than other subgroups defined by race and/or religion. Among Seventh-day Adventists consumption of a vegetarian diet was associated with increased plasma GSH(t) concentration (P = 0.002). Plasma GSH(t) levels also appeared to vary by race, but relationships with race could not be clearly disassociated from relationships with religion. Among white participants plasma GSH(t) concentration decreased with age in women but increased with age in men (P = 0.05). Few other factors were associated with plasma GSH(t) concentration, although use of oral contraceptives (P = 0.10) was somewhat associated with decreased plasma GSH(t) levels. These findings suggest that plasma GSH(t) levels may vary with several demographic and health-related attributes and support the need for further research on this potentially important disease-preventive compound.