Dietary Control of Cortisol Production by Sodium Intake Regulation

Proper cortisol function is necessary for the healthy mammalian response to stressful situations, from occupational pressure to severe trauma. Recently, a number of studies have examined the effects of intravenous cortisol supplementation in patients, resulting in increased survival rates. Intravenous sodium has been shown to increase serum cortisol, and dietary sodium has shown some increase in animal models, but this is the first human diet study examining the effects of dietary sodium on human cortisol levels. Thirty-seven human subjects, ages 18-20, participated in a month-long, double-blind study. Subjects kept diet journals for the duration of the study. Twenty-five journals were returned at the end of the study. Salivary cortisol and blood pressure were measured semiweekly, and subjects reported time since waking, hours of sleep, and perceived stress. Sodium intake alone was significantly different between diet groups. The difference of 961 mg Na/day (3138 mg/day vs. 2177 mg/day) was paired with a trend to higher salivary cortisol (0.545 ug/dL vs 0.490 ug/dL) over the course of the experiment, but was not significant (p = 0.13). The difference was significant over the first 2.5 weeks (0.613 ug/dL and 0.494 ug/dL, p = 0.033). The last 1.5 weeks showed a trend in the other direction (0.387 ug/dL and 0.480 ug/dL, p = 0.090). The data show that for periods of less than three weeks, changes in dietary sodium levels are significantly linked to corresponding changes in cortisol production. Future research may reveal novel treatments using short-term dietary control of cortisol.