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A new study published in PubMed looked at how cocoa flavanols rescue stress-induced declines in endothelial function after a high-fat meal, but do not affect cerebral oxygenation during stress in young, healthy adults.

“We know that when people are stressed, they tend to gravitate towards high-fat foods,” study author Dr. Catarina Rendeiro told us. “We have previously shown that fatty food can impair the body’s vascular recovery from stress. In this study, we wanted to see if adding a high-flavanol food to the fatty meal would alleviate the negative impact of stress in the body."

The research team’s hypothesis was that cocoa flavanols would alleviate the impact of stress and fat combined on vascular function, but they did not know whether it would completely prevent the impairment or just reduce it.

Flavonoid-rich foods (cocoa, tea, berries etc) can have fast beneficial effects within the vasculature, as they get absorbed within one to two hours post ingestion. 

“So I always thought that we could take advantage of that in our daily lives by targeting periods of the day in which the vascular system is at higher risk,” Rendeiro told us. “An example of that is episodes of stress. Stress alone can temporarily impair the vasculature for a couple of hours at a time. We also know that when stressed people do tend to eat fatty and sugary  foods, which we have shown previously that it worsens the effect of stress in the body. So the question was can we do something about it?”

The research team took a group of young healthy adults and gave them two butter croissants with 10 g salted butter, 1.5 slices of cheddar cheese and 250 ml whole milk as breakfast, and either a high-flavanol cocoa or a low-flavanol cocoa drink. Following a rest period, the participants were asked to complete a mental maths to induce psychological stress. This stress task induces significant increases in heart rate and blood pressure, similar to the stress you may encounter in daily life. After the stress was over and blood pressure and heart rate were back to normal (within 30 min), the researchers measured vascular function using Brachial Flow-mediated dilatation (FMD), which is a prognostic measure for future risk of cardiovascular disease.

“We found that when people consumed the fatty foods with the low-flavanol drink when mentally stressed, there was a reduction in vascular function (by 1.29% FMD) and lasted up to 90 minutes after the stressful event was over,” Rendeiro told us. “The findings also showed that the cocoa drink high in flavanols was effective at preventing the decline in vascular function following stress and fat consumption.” 

Brachial flow-mediated dilatation was significantly higher following high-flavanol cocoa compared to low-flavanol cocoa 30 and 90 minutes after the stressful period.

The researchers were surprised that they did not see the beneficial effects in the brain vasculature, but only in the peripheral vasculature. They concluded that a higher number of volunteers would be needed to ascertain the effects in the brain.

“This research shows that drinking or eating a food high in flavanols can be used as a strategy to mitigate some of the impact of poorer food choices on the vascular system,” Rendeiro told us. “This can help us make more informed decisions about what we eat and drink during stressful periods.”  

Although reaching for fatty foods when stressed is not a universal behaviour, it is very common.

“We also know that people tend to shy away from healthy foods when stressed,” Rendeiro told us. “I think strategies like this are important for two reasons: i) On occasions in which making the right food choice when stressed is not possible, adding a healthy flavanol-rich food can at least alleviate the immediate impact of stress and fat on vascular health. ii) Secondly, associating the intake of a healthy food with a specific situation (e.g. stressful meeting) is an easier decision to make than just having healthy foods throughout the day. Behaviour change towards healthier food choices is easier when paired with specific events (If-Then-Planning).”

Recent published guidelines for flavanol intake recommend between 400 to 600 mg/day, which can be achieved for example, by consuming two cups of black or green tea, or a combination of berries, apples and high-quality cocoa.