Elderly people with higher levels of certain vitamins and omega 3 fatty acids in their blood score better on mental sharpness tests than those who eat junk food, a study showed.

Those with a higher intake of trans-fat..did not perform as well on cognitive tests

For eating better may help reduce brain shrinkage commonly associated with Alzheimer’s disease, the findings published by the American Academy of Neurology revealed.

“This approach clearly shows the biological and neurological activity that’s associated with actual nutrient levels, both good and bad,” said Maret Traber, a study co-author.

Researchers at the institute at Oregon State University conducted the study, one of the first of its kind, along with scientists at the Oregon Health and Science University in Portland.

It was carried out among 104 people of an average age of 87 and specifically measured a wide range of blood nutrient levels instead of basing results on food questionnaires, which are less precise and less reliable.

“The vitamins and nutrients you get from eating a wide range of fruits, vegetables and fish can be measured in blood biomarkers,” Dr Traber said.

“I’m a firm believer these nutrients have strong potential to protect your brain and make it work better.”

Researchers noted the positive effects of high levels of vitamins B, C, D and E, as well as the healthy oils most commonly found in fish, on mental quickness and brain size.

Those with a higher intake of trans-fats – commonly found in fried foods, fast foods and other less healthy diet options – did not perform as well on cognitive tests.

Researchers found that while age and education affected performance on the cognitive tests, nutrient status accounted for 17 per cent of the variation in scores, and 37 per cent of the differences in brain volume.

Of those who took part in the study, seven per cent showed a vitamin B12 deficiency, and 25 per cent did not have enough vitamin D in their systems.

Scientists tested 30 different nutrient biomarkers. In addition, 42 participants had MRI scans to measure their brain volume.

“These findings are based on average people eating average American diets,” Dr Traber said.

“If anyone is considering a New Year’s resolution to improve their diet, this would certainly give them another reason to eat more fruits and vegetables.”