Older adults with high levels of omega-3 fatty acids and vitamins B, C, D and E in their blood performed better on certain measures of thinking abilities, and also tended to have larger brain volume, a new study finds.

Seniors with high levels of trans fats in their blood fared worse on certain thinking tests than those with lower levels of the unhealthy fats, and also had more brain shrinkage.

Researchers said the findings suggest that nutrients work "in synergy" with one another to be protective to brain health.

"For people with a vitamin profile high in B, C, D, E, those particular nutrients seem to be working together on some level," said lead study author Gene Bowman, an assistant professor in the Department of Neurology at Oregon Health & Science University in Portland. "Having high scores for those vitamins was associated with better cognitive function and larger brain volume." The study was published in the journal Neurology.

In the study, researchers measured levels of more than 30 nutrients in the blood of 104 people with an average age of 87. Overall, participants were well-educated, healthy nonsmokers who had relatively few chronic diseases and were free of memory and thinking problems. Researchers also did MRI scans of 42 participants to measure their brain volume.

Some amount of brain atrophy, or shrinkage, occurs with aging. More significant shrinkage is associated with mental decline and Alzheimer's disease.

The investigators found that the various nutrients seemed to affect different aspects of thinking, suggesting that they work on different pathways in the brain.

People with high levels of vitamins B, C, D and E performed better on tests of executive function and attention and had better visuospatial skills and global cognitive function. They also had bigger brains, the study authors noted.

Omega-3 fatty acids, which are found in foods such as salmon, were associated with better executive function and with fewer changes to the white matter of the brain, but there was no association between omega-3s and any of the other measures of mental abilities.

"Executive function" is a term used to describe higher level thinking involving planning, attention and problem solving. In this case, seniors were asked to do an exercise that involved matching the number one with the letter A, the number two with B and so on, which shows flexibility in thought, Bowman explained.

White matter changes can be indicative of damage to the small blood vessels of the brain, he said.

The people with high levels of trans fats performed worse on tests of mental abilities and had smaller brains, according to the report.

Dr. Marc Gordon, Chief of Neurology at Zucker Hillside Hospital in Glen Oaks, NY, said the study is "intriguing." While most studies ask people to recall what they ate, in this one, researchers actually measured what participants had absorbed by using blood biomarkers.

"Two issues make this approach more valid," said Gordon, also an Alzheimer's researcher at the Feinstein Institute for Medical Research in Manhasset, NY. "One could be the unreliability of people's recollections about what they ate, and the other is that just because someone ate something doesn't mean they absorbed it."

Neurology; Published online ahead of print.