Diurnal patterns of salivary cytokines differentially correlate with greater fluctuations in cortisol and diet composition: A pilot study

Abstract

Chronic stress and elevated cortisol are associated with adverse metabolic profiles and lifestyle patterns, systemic low-grade inflammation, and increased chronic disease risk; however, it is less clear how the degree of cortisol fluctuations impacts these parameters. Adult men and women (18-70y) were recruited to participate in a 5-day observational study, in which they underwent a baseline health and body composition assessment, completed 5-day diet, exercise, and stress records, and provided saliva samples in the morning, afternoon, and evening to measure fluctuations in cortisol, interleukin-1β (IL-1β), and IL-6. Degree of cortisol variability over the 5-day period (highest cortisol measure - lowest cortisol measure) was used to classify subjects into high (n = 9) and low (n = 9) cortisol fluctuation groups. Participants with greater fluctuations in salivary cortisol had higher salivary cortisol concentrations on average, which was attributed to higher maximal and morning cortisol. A greater proportion of individuals with higher cortisol flux worked in first responder/emergency professions, and exhibited minimal dietary pattern differences compared to those with low cortisol flux. While body fat percentage and mass positively correlated with minimum salivary cortisol measures, body composition and blood pressure did not differ between low vs. high salivary cortisol flux groups. Interestingly, we observed diurnal patterns of salivary IL-1β concentrations, with higher IL-1β in the morning, and greater afternoon IL-1β in the high cortisol flux group compared to the low cortisol flux group. Independent of cortisol flux, waking satiety and intake patterns of dietary nutrients and food groups/type differentially correlated with salivary cytokine concentrations in a time of day-dependent manner. Our findings suggest that greater fluctuations in cortisol are associated with distinct diurnal salivary cortisol and IL-1β concentrations but minimal lifestyle and dietary factors, whereas dietary patterns are strongly and differentially associated with salivary cytokine profiles.

Keywords

• Salivary cortisol
• Cortisol fluctuations
• Lifestyle factors
• Dietary patterns
• Salivary cytokines
• Metabolic profiles