Published in the journal Neurology, the study found elderly people with diets containing high levels of trans fats are more likely to experience a certain type of brain shrinkage associated with Alzheimer's disease than people who consume less of the artery-damaging fats.
The research team, led by Dr Gene Bowman of Oregon Health & Science University, USA, also found that those with high levels of vitamins and omega-3 fatty acids in their blood had better performance on mental alertness tests and showed reduced brain shrinkage.
“High trans fat was associated with less favorable cognitive function and less total cerebral brain volume,” explained Bowman and his team.
They said the results of their analysis had revealed “distinct nutrient biomarker patterns” that accounts for “a significant degree of variance in both cognitive function and brain volume.”
The study is one of the first of its type to specifically measure a wide range of blood nutrient levels, rather than basing findings on less exact data like food intake questionnaires.
Bowman added that the positive effects were seen when people had high levels of vitamins B, C, D, E and omega-3 fatty acids.
Though trace amounts of trans fats are found naturally in dairy and meats, the vast majority are formed during the partial hydrogenation of vegetable oil – that converts the oil into semi-solids for food applications.
Trans fats are attractive for the food industry due to their extended shelf life and flavour stability, and have displaced natural solid fats and liquid oils in many areas of food processing.
However, scientific reports have suggested trans fatty acids raise levels of (bad) LDL-cholesterol, reduce levels of (good) HDL-cholesterol, and influence other risk factors for cardiovascular diseases (CVD).
The links to adverse health, particularly coronary heat disease, has led to a well-publicised bans in Switzerland, and certain US cities such as New York. This has been mirrored with increased pressure on food manufacturers to reformulate products with reduced or removed trans fats.
The new study assessed the blood plasma nutrient levels of 104 healthy participants, with an average age of 87, who had few known risk factors for Alzheimer’s disease.
It was found that those with high levels of trans fats in their blood performed poorly in memory and thinking tests, whilst people with higher levels of vitamin B, C, D and E, and those with high levels of omega-3 fatty acids, performed well in the tests.
The researchers then scanned the brains of 42 participants, finding those with high vitamin levels had larger brains, and those with high trans fats were prone to shrinkage associated with Alzheimer’s.
“It's clear that trans fats are bad - both for your heart and now, we see, for your brain,” said Bowman, who added that although the results need to be confirmed in larger populations, he believes the findings are important.
“Obviously it is very exciting to think that people could potentially stop their brains from shrinking and keep them sharp by adjusting their diet," he said.
Published online ahead of print, doi: 10.1212/WNL.0b013e3182436598
“Nutrient biomarker patterns, cognitive function, and MRI measures of brain aging”
Authors: G.L. Bowman, L.C. Silbert, D. Howieson, H.H. Dodge, M.G. Traber, B. Frei, et al