The trans fats found in your favourite junk foods aren't just clogging your arteries. New research shows they might also be messing with your memory.
Artificially created fats
Young and middle-aged men who ate large amounts of trans fats exhibited a significantly reduced ability to recall words during a memory test, according to findings to be presented at the American Heart Association's annual meeting in Chicago.
Men with the most trans fats in their diet suffered as much as a 10 percent reduction in the words they could recall, the study found.
"The higher the trans fat consumption, the worse the performance," said study author Dr. Beatrice Golomb, a professor of medicine at the University of California, San Diego.
Trans fats are a type of dietary fat that has been shown to both increase blood levels of LDL ("bad") cholesterol and decrease levels of HDL ("good") cholesterol.
Small levels of trans fats naturally occur in milk and meat products, but artificially created trans fats like partially hydrogenated oils are widely used in processed foods, fast food, baked goods, snack foods, frozen pizza and coffee creamers.
Investigating memory function
Golomb said her team decided to investigate trans fats' potential effect on memory following another study they did that found that chocolate improved memory.
"Chocolate is an antioxidant and supports cell energy, which is important to an area of the brain called the hippocampus, which is known to be very important for memory," she said. "We reasoned that since trans fats are pro-oxidant and harmful to cell energy, we felt they might not be good for memory function."
The researchers studied adults who had not been diagnosed with heart disease, including slightly more than 1 000 men aged 20 or older.
Participants completed a dietary questionnaire, from which the investigators estimated their trans fat consumption.
To assess memory, researchers used a proven test called "recurrent words", Golomb said. They presented participants with a series of 104 cards with a word on each. Participants had to state whether each word was new or had already appeared on a prior card.
Read: Trans fatty acids
The researchers found that among men younger than 45, those who ate more trans fats showed notably worse performance on the word memory test, even after taking into account factors such as age, education, ethnicity and depression.
Each additional gram a day of trans fats consumed was associated with an estimated 0.76 fewer words correctly recalled.
"For people at the higher end of consumption, that would translate to 11 to 12 fewer words correctly recalled," Golomb said. The average number of words correctly recalled was 86, so this represents "a pretty big detriment to function", she added.
Oxidizing effects may affect memory
Golomb hypothesizes that the oxidizing effects of trans fats may cause brain cells important to memory to die off. Oxidative stress has been associated with diseases such as heart disease and cancer.
At the same time, the energy-sapping effects of the trans fats may make brain cells more sluggish and less responsive, she added.
"When cells don't get enough energy, they're essentially taken off line," Golomb said.
However, Golomb noted that her study only shows an association between trans fats and memory, not a direct cause-and-effect relationship.
Trans fats already have been shown to have an adverse effect on people's moods and behaviour, and are associated with increased depression and aggression, Golomb said.
Read: Are natural trans fats unhealthy?
Dr. Martha Daviglus, a professor at the University of Illinois College of Medicine and executive director of the Institute for Minority Health Research, said the research shows that "we have to be careful with what we eat because it has consequences."
But Daviglus believes that the potential memory effects of trans fats could be reversed by eating healthy and cutting the bad fats from your diet.
"We are living more and more years, so of course we want to maintain our memory and thinking," she said. "We have to do something to reverse the potential damage."
Research presented at meetings should be viewed as preliminary until published in a peer-reviewed journal.
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