Recently, Petra Wirtz and colleagues from the Department of Psychology, University of Bern, Switzerland demonstrated perhaps for the first time that consumption of dark chocolate is linked to lower stress reactivity.
Evidence indicates a beneficial effect of cocoa flavonoids on cardiovascular health. However, little is known about the effect of dark chocolate consumption on the stress system and its reactivity.
In this study, participants consumed either 50 g of dark chocolate with high cocoa content or an identically looking placebo chocolate without cocoa. The authors found that individuals having high flavonoid levels in the blood expressed low reaction of the adrenal stress hormones cortisol and epinephrine (adrenaline) to a Trier Social Stress Test (TSST).
Interestingly, in another, more recent study, published in Thrombosis and Haemostasis Journal, the same research team has also shown that a consumption of flavonoid-rich dark chocolate blunted the acute prothrombotic response to psychosocial stress.
As psychosocial stress is a known risk factor for cardiovascular disease development, these studies may suggest a peripheral stress-protective effect of dark chocolate consumption. The authors suggest that this may contribute, to some extent, to a reduced risk of acute coronary syndromes triggered by emotional stress.
Source:J Am Coll Cardiol. 2014, 63:2297-9. doi: 10.1016/j.jacc.2014.02.580. Epub 2014 Mar 26. Thromb Haemost 2014; 112(06): 1151-1158 DOI: 10.1160/th14-05-0450
A2016 study represent perhaps the first human study to investigate the effects of acute flavanol-rich dark chocolate intake on the intra- and extracellular inflammatory response to acute psychosocial stress.
The study demonstrates that acute flavanol-rich dark chocolate exerts anti-inflammatory effects both by increasing mRNA expression of the anti-inflammatory cytokine IL-10 and by attenuating stress reactivity of the pro-inflammatory transcription factor NF-κB-BA and of the pro-inflammatory cytokines IL-1β and IL-6 at mRNA-levels.
Yet, in contrast to the intracellular inflammatory measures under study, the investigators could not find a corresponding inhibiting flavanol effect on plasma cytokines.
A 2020 study found that a single oral intake of 85% dark chocolate increased relative values of systolic blood pressure (BP), and double product (DP) at rest but buffered the reactivity of diastolic BP, heart rate (HR), mean arterial BP (MAP), and DP during mental stress, which was not found after ingestion of milk chocolate.
Of note, as per Norman K. Hollenberg et al. wrote, the Kuna Indians were among the first communities described in which hypertension is rare. In fact, as per these authors the very first observation by Kean BH was published in 1944, see the article ‘The blood pressure of the Kuna Indians, the American Journal of Tropical Medicine.
Also, as discussed by Norman K. Hollenberg et al. the Kuna reside in the San Blas Islands, and they have lived on these islands for centuries, but their origin is not completely understood. Recent studies have revealed a remarkably low level of mitochondrial gene diversity, suggesting that there has been remarkably little genetic admixture. This and other epidemiologic studies linked the potential health benefits of dietary flavanols to a reduced cardiovascular risk.
Another2020 studyinvestigated the effect of a polyphenol-rich dietary pattern (comprising fruits, including berries; vegetables and dark chocolate) on aspects of psychological well-being or mental health status, including mood, self-esteem and body image perception.
The participants in the high polyphenol diet (HPD) reported a decrease in depressive symptoms and an improvement in physical component and mental health component scores. No differences in anxiety, stress, self-esteem or body image perception were observed. Thus, the study findings suggest that the adoption of a polyphenol-rich diet could potentially lead to beneficial effects including a reduction in depressive symptoms and improvements in general mental health status and physical health in hypertensive participants.