Ordering a cheeseburger and fries might literally be a dumb move, new research suggests.
A recent, small study from Ohio State University indicates eating a single meal high in saturated fats may hamper your ability to mentally focus.
Saturated fats are found in red meat, dairy products and tropical oils, including coconut and palm. They can raise cholesterol and clog arteries, according to the American Heart Association.
Study author Annelise Madison, a graduate student in clinical psychology, said it's a common belief that food affects your performance.
Fatigue and inflammation
"Anecdotally, a lot of people struggle to focus during the time after lunch," she said.
This study looked at what short-term effect a single meal might have, Madison said.
The study examined data from work done in the lab of her mentor, Janice Kiecolt-Glaser, director of the university's Institute for Behavioral Medicine Research. That earlier study examined if high-fat meals contribute to fatigue and inflammation in cancer survivors.
The new study looked at 51 women given one of two meals: one high in saturated fat, the other high in unsaturated fats. Both meals contained 930 calories and 60 grams of fat. Their mental skills were tested five hours later with a computerised challenge to distinguish targets from distraction. The test was repeated one to four weeks later, with the women fed the opposite of what they ate the first round. Prior to both meals, the women fasted for 12 hours.
Madison's team discovered the women scored 11% lower on the computer test after they had eaten the saturated-fat meal than they had after eating the unsaturated-fat meal made with sunflower oil. In their journal article, the researchers said earlier studies have shown long-term consumption of a high-fat diet can affecting thinking skills.
More research needed
A second finding was women who had high levels of a blood chemical indicating they had a "leaky gut" scored poorly after both meals. This syndrome is somewhat controversial, as not all medical practitioners recognise leaky gut, in which bacteria and toxins are said to leach into the bloodstream from the intestines. Madison questioned whether a regular diet high in saturated fats might contribute to leaky gut.
The study doesn't prove foods high in saturated fat diminish your attention, but it does indicate that may be the case, Madison said. More research is needed to see if the results are replicated with a larger number of participants, male and female, she said.
"We need to look at repeated measures," Madison said.
"This is a small study and a short study, but it is an interesting study," said Connie Diekman, past president of the American Dietetic Association. "We need to follow up."
The findings support longstanding advice of dietitians and other health experts that Americans reduce their intake of saturated fats, said Diekman, a registered dietitian and food and nutrition consultant in St. Louis.
Digestion and metabolism are complex
"It means we need to be eating fruits and vegetables, especially dark, colourful vegetables," she said.
"Diet is extremely important," she continued, urging more reliance upon plant foods, whole grains and less red meat.
As for whether an indicator in the blood shows leaky gut may affect mental abilities, Diekman is less certain. She said it can be difficult to determine the effect of a single biochemical or nutrient in the body. Digestion and metabolism are complex, as are the body's responses, she said.
Amy Rose Sager, a registered dietitian nutritionist in East Sandwich, Massachusetts., said the finding that a single meal high in saturated fat may affect the brain is interesting, but needs more work. She said she would like future research to delve deeper into more specific types of fat and how long the effects of a single meal last.
"We're still trying to limit saturated fat for overall health," she said.
'Your gut can affect your mind'
Sager said the concept that food affects thinking skills is behind the MIND diet, a cross between the Mediterranean diet and the DASH diet. The diet promotes green, leafy vegetables, beans, whole grains and nuts, and restricts sweets, red meat and fats. Olive oil is the preferred fat for cooking under the MIND diet, which is designed to help prevent Alzheimer's disease and age-related dementia.
She said the new study needed to consider participants' oral health when monitoring for evidence of leaky gut.
"Your gut can affect your mind," Sager said.
The study was partly funded by grants from the US National Institutes of Health. The results were published early in May in the American Journal of Clinical Nutrition.
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