Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women

Abstract

Caffeine elevates cortisol secretion, and caffeine is often consumed in conjunction with exercise or mental stress. The interactions of caffeine and stress on cortisol secretion have not been explored adequately in women. We measured cortisol levels at eight times on days when healthy men and women consumed caffeine (250 mg × 3) and underwent either mental stress or dynamic exercise protocols, followed by a midday meal, in a double blind, placebo-controlled, crossover design. Men and women had similar cortisol levels at the predrug baselines, but they responded differently to mental stress and exercise. The cortisol response to mental stress was smaller in women than in men (p=.003). Caffeine acted in concert with mental stress to further increase cortisol levels (p=.011), the effect was similar in men and women. Exercise alone did not increase cortisol, but caffeine taken before exercise elevated cortisol in both men and women (ps<.05). After a postexercise meal, the women had a larger cortisol response than the men, and this effect was greater after caffeine (p<.01). Cortisol release in response to stress and caffeine therefore appears to be a function of the type of stressor and the sex of the subject. However, repeated caffeine doses increased cortisol levels across the test day without regard to the sex of the subject or type of stressor employed (p<.00001). Caffeine may elevate cortisol by stimulating the central nervous system in men but may interact with peripheral metabolic mechanisms in women.

Salivary VIP concentrations are elevated in humans after acute stress

“…"Caffeine acts as an important modulator of cardiovascular and central nervous system activity" (Lovallo et al, 2006). Our results of drinking a cup of coffee on salivary cortisol are somewhat consistent with literature which reports no effect of caffeine on salivary cortisol levels in the absence of stress (Lovallo et al, 2006).…”

“…Therefore these studies suggest that caffeine does not elevate cortisol levels in the absence of stress. (Lovallo et al,2006;Shepard et al, 2000) Another study by Slivka et al (2008) investigators found no effect of 1 week of 1x200mg doses of caffeine supplementation on serum cortisol and serum DHEA levels (Mackenzie et al, 2007).…”

“…In a U.S. polled population, 96% of adults have reported consuming caffeine at some time in their lives and 83% have reported to consume 186 mg of caffeine per day (Lovallo et al, 2006). According to Lovallo et al (2006), caffeine acts as an important modulator of cardiovascular and central nervous system activity.…”

“…According to Lovallo et al (2006), caffeine acts as an important modulator of cardiovascular and central nervous system activity. In addition, certain amounts of caffeine have been reported to elevate blood pressure for several hours after intake and this effect can occur both at rest and during exercise or mental stress (Lovallo et al, 2006). An interesting finding from Lovallo et al (2006) showed that 250mg of caffeine did not actually elevate cortisol levels in the absence of stress.…”

“…In addition, certain amounts of caffeine have been reported to elevate blood pressure for several hours after intake and this effect can occur both at rest and during exercise or mental stress (Lovallo et al, 2006). An interesting finding from Lovallo et al (2006) showed that 250mg of caffeine did not actually elevate cortisol levels in the absence of stress. Lovallo's group observed an increase in salivary cortisol levels when caffeine was administered in conjunction with mental stress or exercise.…”