A poor memory can be a sign of vitamin B12 deficiency, research finds.
People in the study with low levels of vitamin B12 had worse memory for both ideas and events in their lives.
Low levels of vitamin B12 can contribute to brain shrinkage, the study also suggested.
Good sources of vitamin B12 include fish, poultry, eggs and low-fat milk.
Fortified breakfast cereals also contain vitamin B12.
People who may have difficulty getting enough vitamin B12 include vegetarians, older people and those with some digestive disorders, such as Crohn’s disease.
Dr Christine C. Tangney, the study’s first author, said:
“Our findings lend support for the contention that poor vitamin B12 status is a potential risk factor for brain atrophy and may contribute to cognitive impairment.”
For the study, 121 older people were given tests of memory and thinking and had their vitamin B12 levels measured.
Brain scans 4.5 years later revealed brain shrinkage in those who were deficient.
B12 deficiency was also linked to worse scores on cognitive tests.
Dr Tangney said:
“Our findings definitely deserve further examination.
It’s too early to say whether increasing vitamin B12 levels in older people through diet or supplements could prevent these problems, but it is an interesting question to explore.
Findings from a British trial with B vitamin supplementation are also supportive of these outcomes.”
Other, common signs of vitamin B12 deficiency include feeling tired, experiencing muscle weakness and being constipated.
The study was published in the journal Neurology (Tangney et al., 2011).