Macronutrient Ratio of a Meal does not Impact Psychological and Physiological Stress Response

Many people say: "I need my carbs to relax!" But is it actually true that high-carb meals facilitate better stress management? According to a recently published study (Lemmens. 2011) this claim belongs to the realms of nutritional mysticism - at least in the short run.

Subjects (n = 38, 19m/19f, age = 25±9 yrs, BMI = 25.0±3.3 kg/m²) reported to the lab fasted and ingested either a high-carb (-C) or a high-protein (-P) meal before half of them performed a computer based stress test (S-), while the other half served as a "rested" control (R-). Groups were changed and the procedure was repeated.

Figure 1: Salivary cortisol concentrations (mean±SEM) at six time points (0, 30, 80, 125, 155, and 205 min) throughout the four test sessions: rest-carbohydrate (RC), stress-carbohydrate (SC), rest-protein (RP), stress-protein (SP); for men (n = 19, M) and women (n = 19, F). (Lemmens. 2011)

As the measured salivary cortisol levels in figure 1 show the stress response does not depend on the macronutrient composition of the previous meal. Thus, after all, another holdout of the supporters of high carb diets starts to falter.

To be fair, one must however say that the picture might have been a different one if the "stressor" had been an intense weight bearing or endurance exercise. Exercise induced hypoglycemia, for example, would unquestionably have induced a significant amount of cortisol release. Yet, my personal experience tells me that you generally do not run out of fuel if you follow a consequent low carb diet. I tend to run into problems (hypoglycemia) only, when I overdo on carbs - a consequent low carb diet, on the other hand, provides me with a steady stream of energy.