A type of fat found in processed food has been linked to memory loss in working-age men.
Trans-fatty acids, or trans fats, used to improve taste, texture and shelf-life, are known to be associated with an increased risk of heart disease and there is pressure on food manufacturers around the world to remove them.
The new research found that consuming larger amounts of trans fats led to poorer memory in men aged 45 and younger.
It showed that men whose diets contained the highest levels of the fats were likely to recall 12 fewer words in a memory test than those who avoided them.
US lead researcher Beatrice Golomb, from the University of California at San Diego, said trans fats were most strongly linked to worse memory in men during their high productivity years.
Trans-fat consumption has previously shown adverse associations to behaviour and mood – other pillars of brain function. However, to our knowledge a relation to memory or cognition had not been shown.
She added: “As I tell patients, while trans fats increase the shelf life of foods, they reduce the shelf life of people.
The team analysed data from 1,018 men and women who were asked to complete a dietary survey and take part in word recall memory tests.
On average, men aged 45 and younger were able to recall 86 words in the tests. But for each additional gram of trans fat they consumed each day, their performance reduced by a statistical 0.76 words.
This translated to young men being able to recall around 12 fewer words if their trans-fat consumption matched the highest levels seen in the study, said the scientists.
The findings are published in the online journal Public Library of Science One. Although the trend was only significant for men, this may only have been due to the small number of women participants in the same age group, they pointed out.
The association was not seen in older populations, possibly because it was masked by the effects of age on memory.
An announcement from US regulators means that most trans fats will be removed from American foods within three years.
The Food and Drug Administration (FDA) said partially hydrogenated oils (PHOs) – the main source of trans fats – are not generally recognised as safe.
The move is likely to prevent thousands of fatal heart attacks each year, according to experts.
In Denmark, almost all trans fats have been banned since 2003 but in the UK their removal depends on food manufacturers signing up to a voluntary scheme.