Just one fatty meal affects our concentration, research suggests.
Scientists from the Ohio State University gave 51 women an American-style fry-up, complete with eggs, turkey sausage, and savoury biscuits and gravy.
Some of the meals were cooked with palm oil, while the remainder were prepared with the more heart-healthy sunflower oil.
Results reveal the women who consumed the sunflower-oil based breakfast performed significantly better on an attention test.
Read more: What does a ‘healthy food day’ look like?
“Most prior work looking at the causative effect of the diet has looked over a period of time and this was just one meal,” said lead author Annelise Madison.
“It's pretty remarkable that we saw a difference.”
Both meals contained 930 calories, similar to fast-food favourites like the Burger King double whopper with cheese or a McDonald's Big Mac with medium fries.
The women sat the attention test before eating and five hours later.
Between one and four weeks later, the women went back to the testing site, this time eating the opposite dish to what they consumed the first time.
Before each visit, the women ate three standard meals and then fasted for 12 hours.
The results – published in the American Journal of Clinical Nutrition – show that after eating the fattier meal, the women were on average 11% less able to detect target stimuli in the attention test.
This remained true after the scientists took into account other factors that can influence cognition, like depression.
Although unclear, the scientists wondered whether saturated food triggers inflammation, which may reach the brain.
“It could be that fatty acids are interacting with the brain directly,” said Madison.
With anxiety high amid the coronavirus outbreak, the scientists worry people may be tempted to overindulge.
“What we know is when people are more anxious, a good subset of us will find high-saturated-fat food more enticing than broccoli,” said study author Professor Janice Kiecolt-Glaser,.
“We know from other research that depression and anxiety can interfere with concentration and attention as well.
“When we add that on top of the high-fat meal, we could expect the real-world effects to be even larger.”
Read more: How severe is the obesity crisis?
The scientists also found the participants’ attention was particularly impaired when they showed signs of “leaky gut syndrome”.
The NHS does not recognise leaky gut as a medical condition.
Some claim it comes about when the immune system reacts to germs, toxins or other substances that have been absorbed into the bloodstream via a porous bowel.
This then supposedly triggers everything from migraines to asthma.
The NHS states there is “little evidence to support the theory that a porous bowel is the direct cause of any significant, widespread problems”.