Research finds flavanol-rich cocoa and green tea can protect the body’s vasculature from stress after high-fat food

Food choices made during periods of stress can influence cardiovascular health. A new study in Food and Function found that drinking cocoa high in flavanols in combination with a fatty meal can counteract some of the impact of fatty food and protect the vascular system from stress. 

“We know that when people are stressed, they tend to gravitate toward high-fat foods. We have previously shown that fatty food can impair the body’s vascular recovery from stress,” says lead author Dr. Catarina Rendeiro, assistant professor in Nutritional Sciences at the University of Birmingham, UK.

“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.”

Effects of fatty meal on mental performance

Flavanols are a type of compound that occurs in different fruits, vegetables, tea and nuts, including berries and unprocessed cocoa. Flavanols are known to have health benefits, particularly for regulating blood pressure and protecting cardiovascular health.

The researchers took a group of young, healthy adults and gave them two butter croissants with 10 g of salted butter, 1.5 slices of cheddar cheese and 250 ml of whole milk as breakfast, and either a high-flavanol cocoa or a low-flavanol cocoa drink.

Following a rest period, they asked the participants to complete a mental math test, which increased in speed for eight minutes, alerting them when they got an answer wrong.

“During the eight minute rest period and eight minute mental math test, we measured forearm blood flow, cardiovascular activity and prefrontal cortex tissue oxygenation,” says Rosalind Baynham, first author of the paper.

“We also measured vascular function using brachial flow-mediated dilatation (FMD), which is a prognostic measure for future risk of cardiovascular disease. This stress task induced significant increases in heart rate and blood pressure, similar to the stress you may encounter in daily life.”

Alkalized vs non-alkalized cocoa

The cocoa beverages were prepared by dissolving 12 g of cocoa powder into 250 ml of whole milk. The low-flavanol cocoa powder was alkalized, which was processed to reduce total flavanols to 5.6 mg per serving, and the high-flavanol cocoa powder was non-alkalized, delivering 695 mg total flavanols per serving. 

Alkalization was found to reduce the amount of beneficial flavanols in cocoa.Alkalization is a process typically used in chocolate making to enhance flavor, but unfortunately, it was found to reduce the amount of flavanols.

The team confirmed that consuming fatty foods with the low-flavanol drink when mentally stressed reduced vascular function (by 1.29% FMD) and lasted up to 90 minutes after the stressful event was over. 

The findings also showed that cocoa drinks high in flavanols were 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. 

In their previous work, the team found high-fat foods reduced oxygen delivery in the prefrontal cortex during stress. However, cocoa flavanols did not improve cerebral oxygenation or impact mood.

“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. This can help us make more informed decisions about what we eat and drink during stressful periods,” says Rendeiro.

Flavanol intake

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.

“Modern life is stressful and the impact of stress on our health and the economy has been well documented, so any changes we can make to protect ourselves from some of the symptoms of stress is positive,” says paper author Jet Veldhuijzen van Zanten, professor of Biological Psychology at the University of Birmingham.

“For those who tend to reach for a treat when stressed or depend on convenient food because they work high-pressure jobs or are time-poor, incorporating some of these small changes could make a real difference.”