Coffee is one of the most widely consumed beverages. It contains many biologically active compounds including caffeine and a number of antioxidants. In addition to the stimulant effects of caffeine, coffee elevates the levels of the hormone cortisol. Cortisol plays a key role in the stress response and is a critical modulator of metabolism.
A single cup of coffee can significantly elevate cortisol levels. Elevations result from caffeine’s effects at the level of the hypothalamus, a critical brain structure in regulating hormone levels. Caffeine increases stimulating hormones, which act on the pituitary and adrenal glands to ultimately increase cortisol release. Coffee also regulates the degradation of cortisol at the tissues including liver, muscle and fat.
Cortisol affects many body systems including bone, the circulatory system, immune responses, and metabolism. In particular, elevated cortisol levels contribute to increases in weight gain by mobilizing fatty acids to abdominal fat depots.
Additionally, cortisol increases blood pressure and thus the work of the heart. Repeated elevations in blood pressure can contribute to hypertension and cardiovascular disease. Excess cortisol also leads to immune suppression and increases the susceptibility to infection and cancer.
Coffee, Cortisol and Diabetes
While the causative agents and exact mechanisms of action remain to be elucidated, a series of studies demonstrated that coffee improves clinical measures for diabetes including glucose tolerance and insulin sensitivity.
Coffee produces these benefits despite a negative impact on obesity, a risk factor for the development of Type 2 diabetes. Coffee’s effect on local cortisol metabolism, particularly in metabolically active tissues, appears to play a role in this benefit.
Further studies will be needed, however, to satisfy the apparent discrepancy between the effects of caffeine, which impairs glucose tolerance, and the protective effects of coffee on the development of Type 2 diabetes.
Coffee, Cortisol and Heart Disease
Both caffeine and the elevations in cortisol elicited by coffee can increase blood pressure, contributing to hypertension. However, moderate coffee consumption has recently been shown to reduce the risk of heart disease.
While promising, these preliminary studies do not yet provide enough information to make recommendations on potential protective effects of coffee on cardiovascular disease. As with the benefit observed in markers of diabetes, additional studies will be needed to determine the mechanisms of protection despite increases in blood pressure.
The wide ranging effects of caffeine and other biologically active compounds in coffee on cortisol and other body systems suggests a careful approach to its use. Normal dietary doses do not appear to pose any significant risk, however, and emerging evidence suggests benefit of moderate coffee consumption on the prevention of heart disease and Type 2 diabetes.