May 2018 Issue

Ask the Expert: The Cortisol Connection
By Toby Amidor, MS, RD, CDN
Today's Dietitian
Vol. 20, No. 5, P. 9

Q: Many of my clients have been asking about the relationship between certain foods and the body's cortisol levels. Does food intake have any influence on the level of cortisol in the body, or vice versa?

A: Research findings on this issue are mixed and conflicting. There appears to be an association between higher cortisol levels and less healthful food choices (ie, choosing less healthful foods possibly due to increased cortisol); however, there's less evidence that food choices affect cortisol levels.

What Is Cortisol?
When the brain detects a threat, it triggers the release of a series of hormones including adrenaline, corticotropin-releasing hormone (CRH), and cortisol. In the short term, adrenaline, the "flight or fight" hormone, prepares the body to handle the threat at hand, while CRH suppresses hunger. However, if the stress continues long term, the body releases cortisol. Studies link changes in food selection to higher cortisol levels in individuals under stress.

A 2006 study investigated the effects of stress on food choice.1 Researchers found that stress decreased the selection of healthful, lower-fat meals and increased the consumption of less healthful, high-fat foods. However, from this study it's unclear whether these food choices were related to cortisol levels.

A 2010 study examined the effects of pharmaceutical-induced cortisol response on food intake.2 Subjects were infused with CRH, which elicits the release of cortisol, and subsequent snack food intake was documented and analyzed. The subjects ate more following CRH administration compared with placebo. It appears that cortisol may have an effect on appetite and cravings, and, if so, cortisol may indirectly influence appetite by modulating other hormones and stress responsive factors known to stimulate appetite.3 However, many clients inquire whether appetite may impact cortisol levels.

Do Specific Foods Influence Cortisol?
A 2011 study published in PLoS ONE examined the effects of meal consumption with different macronutrient contents on physiological and psychological responses.4 This randomized crossover study investigated the effects of high-protein vs high-carbohydrate consumption, with one-half of the participants in each group introduced to stress by means of a psychological computer test. Researchers found that cortisol levels didn't differ between the two groups, regardless of stress levels. As such, the researchers concluded that the type of diet doesn't result in different physiological or psychological responses. A 2007 study published in the Annals of Nutrition & Metabolism looked at hormonal response to fast food meals compared with healthful, balanced meals.5 In this three-way crossover design study, a standard breakfast was provided to all subjects, and then one of three choices was provided—a fast food meal, an organic beef meal, and a turkey meal with orange juice. The data revealed no difference in hormonal response to the meals. A 2010 study published in Physiology & Behavior looked at the effects of macronutrient intake on cortisol levels.6 Results showed that cortisol response to carbohydrate consumption was significantly higher when compared with controls, but the decrease in cortisol seen after protein or fat consumption was no different than that of the control group.

Other recent studies have shown that cortisol has no major influence on long-term calorie restriction7 or physical fitness levels.8 In addition, a 2016 study looked at cortisol levels after subjects consumed a control breakfast vs a moderately low-carbohydrate breakfast given randomly after a 10-hour fast.9 The results found that cortisol levels changed before and after breakfast, but the change was similar among the two breakfasts.

Recommendations for Clients
With conflicting evidence, it's unclear whether food intake impacts cortisol levels. As a result, dietitians can't provide clear evidence-based dietary recommendations to clients who seek foods to help lower cortisol levels. A well-balanced, calorie-controlled diet limiting added sugars, sodium, and saturated fat (per the 2015–2020 Dietary Guidelines for Americans) always can be recommended, and barriers for consuming such a diet can be explored, focusing on the emotional aspect of eating. The nutrition professional also can inquire about anxiety or other such disorders, and make a referral to a psychologist for further evaluation if deemed appropriate.

— Toby Amidor, MS, RD, CDN, is the founder of Toby Amidor Nutrition (http://tobyamidornutrition.com) and the author of the cookbooks The Easy 5-Ingredient Healthy Cookbook, The Healthy Meal Prep Cookbook, and The Greek Yogurt Kitchen. She's a nutrition expert for FoodNetwork.com and a contributor to US News Eat + Run and MensFitness.com.


References
1. Zellner DA, Loaiza S, Gonzalez Z, et al. Food selection changes under stress. Physiol Behav. 2006;87(4):789-793.

2. George SA, Khan S, Briggs H, Abelson JL. CRH-stimulated cortisol release and food intake in healthy, non-obese adults. Psychoneuroendocrinology. 2010;35(4):607-612.

3. Aronson D. Cortisol — its role in stress, inflammation, and indications for diet therapy. Today's Dietitian. 2009;11(11):38-41.

4. Lemmens SG, Born JM, Martens EA, Martens MJ, Westerterp-Plantenga MS. Influence of consumption of a high-protein vs. high-carbohydrate meal on the physiological cortisol and psychological mood response in men and women. PLoS One. 2011;6(2):e16826.

5. Bray GA, Most M, Rood J, Redmann S, Smith SR. Hormonal responses to a fast-food meal compared with nutritionally comparable meals of different composition. Ann Nutr Metab. 2007;51(2):163-171.

6. Martens MJ, Rutters F, Lemmens SG, Born JM, Westerterp-Plantenga MS. Effects of single macronutrients on serum cortisol concentrations in normal weight men. Physiol Behav. 2010;101(5):563-567.

7. Fontana L, Villareal DT, Das SK, et al. Effects of 2-year calorie restriction on circulating levels of IGF-1, IGF-binding proteins and cortisol in nonobese men and women: a randomized clinical trial. Aging Cell. 2016;15(1):22-27.

8. Jayasinghe SU, Torres SJ, Fraser SF, Turner AI. Cortisol, blood pressure, and heart rate responses to food intake were independent of physical fitness levels in women. Appl Physiol Nutr Metab. 2015;40(11):1186-1192.

9. Ohlsson B, Darwiche G, Roth B, Höglund P. Two meals with different carbohydrate, fat and protein contents render equivalent postprandial plasma levels of calprotectin, cortisol, triglycerides and zonulin. Int J Food Sci Nutr. 2016;67(7):872-880.

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