In two new studies, University of Birmingham researchers found that eating high-fat foods during periods of mental stress attenuated cerebral oxygenation in the pre-frontal cortex, resulting in a depletion of oxygen delivery (39% reduction in oxygenated hemoglobin) compared to consuming a low-fat meal.
"When we get stressed, different things happen in the body: our heart rate and blood pressure go up, our blood vessels dilate, and blood flow to the brain increases,” said Rosalind Baynham, from the University of Birmingham. “We also know that the elasticity of our blood vessels – which is a measure of vascular function – declines following mental stress. We found that consuming fatty foods when mentally stressed reduced vascular function by 1.74% (as measured by Brachial Flow-mediated dilatation, FMD)."
This vascular function was reduced for up to 90 minutes after the stress subsided. The good news, however, is that eating foods high in polyphenols, such as cocoa, berries, grapes, apples and other fruits and vegetables had no impact on vascular function.
To gauge their findings in a human trial, the researchers recruited young, healthy adults and gave them two butter croissants each for breakfast.
”We then asked them to do mental math, increasing in speed for eight minutes, alerting them when they got an answer wrong,” said Baynham. “They could also see themselves on a screen while they did the exercise. The experiment was designed to simulate everyday stress that we might have to deal with at work or at home.
"Previous studies have shown that a 1% reduction in vascular function leads to a 13% increase in cardiovascular disease risk,” she added. “Importantly we show that this impairment in vascular function persisted for even longer when our participants had eaten the croissants."
The good news? Opting instead for low-fat food and drink, while still poorly impacting vascular function (1.18% decrease), it didn’t take long for the body to bounce back to normal after the stress subsided.
“To see such a significant difference in how their bodies recover from stress when they eat fatty foods is staggering,” said Jet Veldhuijzen van Zanten, professor of Biological Psychology at the University of Birmingham. “For people who already have an increased risk of cardiovascular disease, the impacts could be even more serious."
As such, the researchers warn that reaching for high-fat snacks to cope with stressful work or life situations might actually be a bigger danger to health than previously thought.
"We all deal with stress all the time, but especially for those of us in high-stress jobs and at risk of cardiovascular disease, these findings should be taken seriously,” said Veldhuijzen van Zanten. “This research can help us make decisions that reduce risks rather than make them worse."
That’s not all, however. Reduced oxygenation can result in bad moods or other mental health issues, which can make stress even worse, compounding health issues.
"We know that when people are stressed, they tend to gravitate towards higher-fat foods, either because it is the more convenient option if time is in short supply or as a treat to deal with the stress,” said Catarina Rendeiro, Professor in Nutritional Sciences at the University of Birmingham. “But by doing this, they are making their physical and psychological response to stress worse.”
Reaching for low-fat foods is both best for relieving stress and lessening the physiological impact.
"The world is an incredibly stressful place right now, and even without outside factors such as war or a cost-of-living crisis, stress is something we all need to deal with,” said Baynham. “So, next time you are in a big meeting or taking part in a job interview, maybe try and resist the free biscuits and go for some berries instead. You might find you feel more relaxed and can cope with the stress just a little bit better."
The research was published in the journals Frontiers in Nutrition and Nutrients.
Source: University of Birmingham/New Atlas
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