The effects of a high carbohydrate diet on cortisol and salivary immunoglobulin A (s-IgA) during a period of increase exercise workload amongst Olympic and Ironman triathletes

Int J Sports Med. 2005 Dec;26(10):880-5. doi: 10.1055/s-2005-837467.


The present study observed the effects of a 6-day high carbohydrate (H-CHO) diet on salivary cortisol and IgA during a period of increased exercise workload. Thirty-two competitively trained male triathletes were randomly allocated into a self-selected (SS), or an H-CHO (12 g CHO kgbm (-1) . day (-1)) dietary group. In addition to their training regimes, all subjects performed a 1-hour running exercise bout at 70 % V.O (2max) . d (-1), for six days. Saliva samples were taken pre, immediately post, and morning post-exercise bout on days 1, 4, and 6. The concentrations of s-IgA and cortisol were determined by ELISA assays. There was a significant (p < 0.001) interaction between Group x Time for cortisol, with a marked increase in concentrations occurring in the SS dietary group pre to post exercise, and pre to morning post-exercise (p < 0.01). Conversely, a significant (p = 0.009) Group x Time interaction reflected higher post exercise s-IgA concentrations (p < 0.005) than pre exercise in the H-CHO diet group. Blood glucose concentration decreased pre to post exercise in the SS diet group (p < 0.01), whilst remaining stable in the H-CHO group. It is concluded that the consumption of a high CHO diet throughout a 6-day period of overtraining had a favourable effect on markers of immune activity and thereby reduced the susceptibility of these endurance athletes to upper respiratory tract infection URTI.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Blood Glucose / analysis
  • Dietary Carbohydrates / administration & dosage*
  • Energy Intake / physiology
  • Enzyme-Linked Immunosorbent Assay
  • Exercise / physiology*
  • Humans
  • Hydrocortisone / analysis*
  • Immunoglobulin A / analysis*
  • Male
  • Physical Endurance / physiology
  • Saliva / chemistry*
  • Saliva / immunology*
  • Time Factors


  • Blood Glucose
  • Dietary Carbohydrates
  • Immunoglobulin A
  • Hydrocortisone