Eating oily fish and other sources of omega-3 fatty acids may preserve brain health and enhance thinking skills in middle age, a new study suggests.

Researchers found that people who have higher levels of omega-3 in their blood during midlife have better cognition than people who have lower levels of the fatty acid.

The study in the US also found that omega-3 intake in midlife is linked to better brain structure.

Commentators said that having a healthy brain in midlife is important for brain health in later life.

The new contribution here is that even at younger ages, if you have a diet that includes some omega-3 fatty acids, you are already protecting your brain for most of the indicators of brain aging that we see at middle age

The new study, published in the journal Neurology, examined almost 2,200 people in their 40s and 50s with an average age of 46.

The team of experts examined the amount of omega-3 fatty acid in the blood and compared it to MRI and “cognitive markers of brain aging”.

They found that people with higher levels of the fatty acid had “higher hippocampal volumes”, the hippocampus is part of the brain which plays a major role in learning and memory.

Higher levels of omega-3 was also linked to better thinking skills including the ability to understand complex concepts using logical reasoning.

“Studies have looked at this association in older populations,” said lead author of the study Claudia Satizabal, assistant professor of population health sciences at the University of Texas Health Science Centre.

“The new contribution here is that even at younger ages, if you have a diet that includes some omega-3 fatty acids, you are already protecting your brain for most of the indicators of brain aging that we see at middle age.”

Commenting on the study, Dr Sara Imarisio, head of research at Alzheimer’s Research UK, said: “As the saying goes, ‘You are what you eat’, and just like other parts of the body our brains can be affected by the way we live our lives, including our diet.

“In this study, scientists looked at omega-3 fatty acid levels in the blood of people who did not have dementia, finding higher levels were more common in those with better brain structures.

“Of course, this doesn’t prove that high omega-3 is the reason for the differences in the scans.

“Research into omega-3 and brain health has produced mixed results and while this study adds to the evidence base, it is exploratory and not conclusive.

“And because it only looked at people in middle age, this study only offers a snapshot of the full story, it did not look to see whether people went on to develop conditions like dementia.

“What we do know is that a healthy brain in midlife is important for brain health in later life too and that a healthy diet overall is important in reducing dementia risk.

“Our research has shown that only a third (33%) of people think it’s possible to reduce their risk of dementia.

“However, up to 40% of dementia cases could be avoidable through health and lifestyle choices we can influence.

“As well as having a balanced diet, the best current evidence to keeping your brain healthy as you age include not smoking, staying mentally and physically active, only drinking in moderation and keeping blood pressure and cholesterol in check.”