Increased salivary cortisol reliably induced by a protein-rich midday meal

Psychosom Med. Mar-Apr 1999;61(2):214-24. doi: 10.1097/00006842-199903000-00014.


Objective: This study was conducted to determine whether an increase in salivary free cortisol would be reliably elicited by a midday meal, thus providing a convenient physiological challenge to the hypothalamic-pituitary-adrenal (HPA) axis, and whether this cortisol release depended on the protein content of the meal.

Method: In healthy men, free cortisol was measured in saliva samples taken before and after two identical protein-rich midday meals (39% energy as protein) and compared with a day on which no meal was eaten. Next, in healthy women in a nonclinical setting, salivary cortisol was measured before and after a protein-rich meal (32% energy as protein) on one day and a low-protein meal (5% energy as protein) on another day. Measures of mood, appetite, and psychological well-being were also taken.

Results: An acute meal-dependent increase in salivary cortisol occurred, which was reliable over 2 test days. This increase in cortisol depended on the proportion of protein in the meal, increasing after the high-protein but not the low-protein meal. The extent of this increase in cortisol correlated significantly with poor psychological well-being in women. Some postmeal improvement of mood (positive affect) was associated with the high- but not the low-protein meal.

Conclusions: The cortisol response to meals may have implications for the effects of meal composition on mood, cognitive function, and food choice. The measurement of free cortisol in saliva provides a psychologically stress-free and reliable technique to assess the cortisol response to a standard protein-rich meal, ie, a physiological challenge to the HPA axis in men and women that could be investigated in naturalistic settings outside the laboratory.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Diet*
  • Dietary Proteins / analysis*
  • Energy Intake
  • Feeding Behavior
  • Female
  • Humans
  • Hydrocortisone / analysis*
  • Hypothalamo-Hypophyseal System / metabolism
  • Male
  • Middle Aged
  • Nutritional Physiological Phenomena
  • Pituitary-Adrenal System / metabolism
  • Saliva / chemistry*
  • Stress, Psychological / psychology
  • Surveys and Questionnaires
  • Time Factors


  • Dietary Proteins
  • Hydrocortisone