Research appearing in Biological Trace Element Research (1990;24:83-89) looked at zinc supplementation and cortsol production. In the past, high levels of zinc in the blood and low levels of zinc in the blood have both shown to have an effect on  adrenal secretion. The subjects of the study were 27 healthy patients, between the ages of 20 and 27. The men and women were randomly divided into two groups with 13 receiving zinc and 14 receiving a placebo. Fasting cortisol was taken at 7:00 AM and either zinc (25 mg, 37.5 mg or 50 mg) or a placebo were given at 8:00 AM. Blood samples wee taken over the next four hours. Researchers found that zinc had an acute inhibitory effect on cortisol secretion during that time.