title: 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.
abstract: 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.
authors.affiliation: Chester Centre for Stress Research, and Department of Sport and Exercise Science, University College Chester, Parkgate Road, Chester CH1 4BJ, England, UK.
authors.forename: R J S
authors.initials: RJ
authors.lastname: Costa
authors.forename: G E
authors.initials: GE
authors.lastname: Jones
authors.forename: K L
authors.initials: KL
authors.lastname: Lamb
authors.forename: R
authors.initials: R
authors.lastname: Coleman
authors.forename: J H H
authors.initials: JH
authors.lastname: Williams
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D002149:Energy Intake / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D007070:Immunoglobulin A / Q000032:analysis*; D008297:Male; D010807:Physical Endurance / Q000502:physiology; D012463:Saliva / Q000737:chemistry* / Q000276:immunology*; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007070:Immunoglobulin A; D006854:Hydrocortisone