The scientists at Oxford University say vitamin B12 may protect against brain volume loss as people age.

In a study involving 107 people between the ages of 61 and 87, brain scans, tests of memory and physical exams were carried out as well as blood tests in order to check vitamin B12 levels - none of the study participants had a vitamin B12 deficiency.

The brain scans and memory tests were performed again five years later and the study revealed that people who had higher vitamin B12 levels were six times less likely to experience brain shrinkage compared with those who had lower levels of the vitamin in their blood.

The researchers say many factors which affect brain health are thought to be out of our control, but this study suggests that simply adjusting our diets can perhaps save our memory.

Researcher Anna Vogiatzoglo suggests that consuming more vitamin B12 by eating meat, fish, fortified cereals or milk may be something which can easily be done to prevent brain shrinkage.

Ms Vogiatzoglou says research shows that vitamin B12 deficiency is a public health problem, especially among the elderly, so more vitamin B12 intake could help reverse this problem.

But she does acknowledge that a clinical trial would be needed to determine whether B12 supplementation would actually make a difference in elderly persons at risk for brain shrinkage.

Previous research on the vitamin has had mixed results and few studies have been done specifically with brain scans in elderly populations and Vogiatzoglou says the study did not look at whether taking vitamin B12 supplements would have the same effect on memory.

Some research has suggested that two out of five people are deficient in the vitamin.

Experts say brain shrinkage is usually associated with the development of dementia and it may be useful to include tests of vitamin B levels in the general assessment of health of older individuals.

They say it is crucial for people to lead a healthy lifestyle, with a balanced diet rich in B vitamins and antioxidants and reduce the risk of developing dementia by keeping active, not smoking and keeping an eye on blood pressure and cholesterol.

Professor David Smith, director of the Oxford Project says a trial of B vitamins in the elderly to see if taking them could slow brain shrinkage, is now being planned.

The research was part of the 'Oxford Project to Investigate Memory and Aging' by Oxford University and is published in the current issue of Neurology, the medical journal of the American Academy of Neurology.