Increasing dietary carbohydrate as part of a healthy whole food diet intervention dampens eight week changes in salivary cortisol and cortisol responsiveness

Authors: SOLTANI, HODA - University Of California, Davis; Keim, Nancy; Laugero, Kevin

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2019
Publication Date: 10/24/2019
Citation: Soltani, H., Keim, N.L., Laugero, K.D. 2019. Increasing dietary carbohydrate as part of a healthy whole food diet intervention dampens eight week changes in salivary cortisol and cortisol responsiveness. Nutrients. 11(11). https://doi.org/10.3390/nu11112563.
DOI: https://doi.org/10.3390/nu11112563

Interpretive Summary: Very little is known about how whole food diets, such as those based on the Dietary Guidelines for Americans (DGA), influence chronic psychological stress and its related physiological response. To better understand the effects of whole diets on the stress hormone, cortisol, we examined in a randomized control trial effects of a DGA based diet on circulating cortisol. A randomized, double-blind, controlled 8-wk intervention was conducted in overweight and obese women randomly assigned to one of two diet groups, a diet based on the 2010 DGA or a diet more typical of the American (TAD). While 8-wk change in both markers of stress did not differ between the DGA and TAD groups, there were strong inverse associations between 8-wk change in stress and improvements in certain dietary components of diet quality (lower sodium and higher vegetable consumption). That is, improvements in vegetable and sodium consumption were related to lower stress. Our findings suggest that carbohydrate consumption as part of a healthy whole food diet may help minimize over-exposure to cortisol and its effects to increase hunger for comfort foods. This study provides further evidence for the health benefits of a whole food diet based on the Dietary Guidelines for Americans. We further extend a growing body of support for the suppressive effects of dietary carbohydrate on circulating cortisol and stress-associated cortisol reactions. Our findings provide new information that might help to inform on key food groups that facilitate improved adherence to healthy changes in diet, which are often fleeting.

Technical Abstract: Very little is known about how whole food diets, such as those based on the Dietary Guidelines for Americans (DGA), influence psychological stress and stress system responsiveness. To better understand the effects of whole diets on stress system responsiveness, we examined in a randomized control trial effects of a DGA based diet on cortisol responsiveness. A randomized, double-blind, controlled 8-wk intervention was conducted in overweight and obese women randomly assigned to one of two diet groups, a diet based on the 2010 DGA or a diet based on a Typical American Diet (TAD). During a test week that occurred once at baseline and again after 8 weeks of the intervention, we assessed salivary cortisol collected at 14 selected times across the day, including upon awakening, bedtime, and during a test visit administered standardized social stress task (Trier Social Stress Test, TSST). There were no statistical differences between the diet groups in salivary cortisol at baseline or after 8 wks. However, when considering differences in dietary carbohydrate, but not fat or protein, from the pre-intervention (habitual) to the intervention period, there was a significant (P = 0.0001) interaction between diet group, intervention week, saliva sample, and level of intervention based change in carbohydrate consumption. This interaction was reflected primarily by an 8-wk reduction in salivary cortisol during a period just prior to (log -0.35 ± 0.12 nmol/L) and 30 (log -0.49 ± 0.12 nmol/L), 60 (log -0.50 ± 0.13 nmol/L), 90 (log -0.51 ± 0.13 nmol/L), and 120 (log -0.4476 ± 0.1231 nmol/L) min. after the TSST in the DGA Group with the highest increase (90th percentile) in carbohydrate consumption. In support of this finding, we also found significant (P < 0.05) and inverse linear associations between dietary carbohydrate and log salivary cortisol, with the strongest negative association (ß: -0.004 ± 0.0015, P = 0.009) occurring at 30 min. post-TSST, but only in the DGA group and at wk 9 of the intervention. Together, increasing dietary carbohydrate as part of a DGA based diet may reduce circulating cortisol and dampen psychological stress-related cortisol responsiveness.