Foods rich in the nutrient choline may help protect your brain from the effects of ageing.

The nutrient is found in foods such as chicken, eggs, fish and milk as well as certain legumes such as soy and kidney beans.

Researchers from Boston University discovered that people who included plenty of choline in their diets performed better on memory tests and were less likely to show brain changes associated with dementia.

Senior researcher, Dr Rhoda Au, said the findings suggest that your lifetime diet may have an impact on how your brain ages.

However, she warned that that no single nutrient is a magic bullet against dementia.

"I think the message is that eating a healthy, balanced diet in mid-life is important," she said.

Researchers examined data from a long-running heart health study when referring to their own findings.

Almost 1,400 adults aged 36 to 83 answered dietary questionnaires between 1991 and 1995. Then, between 1998 and 2001, they underwent tests of memory and other cognitive abilities, and had MRI brain scans

The study found that those in the top quarter for choline intake performed better on the memory tests than those in the bottom quarter, even when factors such as education and fat and calorie intake were taken into consideration.

Au said people who didn't consume much choline would not notice an "appreciable difference" day to day.

But findings suggest that people with lower choline intakes were more likely to be on a "pathway" toward mental decline than their counterparts with higher intakes.

Even though the study does not conclusively prove choline protects the memory there is reason to believe that choline matters. The nutrient is a precursor to the brain chemical acetylcholine, which plays a key role in memory and other cognitive functions; low acetylcholine levels are associated with Alzheimer's.

Au concluded that more research was required in this promising area.