Young children may have more cognitive problems if they have low levels of vitamin B12, a new study has found.

According to the findings, those with low levels of the vitamin have more difficulties with cognitive tests such as recognising letters and doing puzzles. They are also not as good at interpreting other children's feelings.

Vitamin B12 is important for a number of reasons, including the proper functioning of nerve tissues and the brain. It is found naturally in animal products such as meat, fish, eggs and dairy products. This is why vegans are particularly at risk of B12 deficiency.

B12 deficiency is also particularly prevalent in some low-income countries where people consume limited amounts of animal products, so a group of international researchers set out to assess the impact of this on young children.

They collected blood from 500 infants in Nepal in order to measure their B12 status. Five years later, they contacted 320 of the children and carried out developmental and cognitive tests on them.

They found that those who had a poor B12 status as infants were more likely to have difficulties with cognitive tests, such as interpreting complex geometrical figures and recognising other children's emotions.

The researchers from Nepal, Norway and the US suggested that an early deficiency in B12 may delay or impair brain development in young children.

"It's like a hidden deficiency of the vitamin in these children's bodies, making their cells work rigorously to signalise imminent danger. Our study is one contribution in the big puzzle to understand the implications low B12 levels might have on small children's cognitive development," commented one of the researchers, Ingrid Kvestad, of Uni Research in Bergen, Norway.

Details of these findings are published in the American Journal of Clinical Nutrition.