New Delhi: One in three adolescents in the National Capital Region suffers from vitamin B12 deficiency, which raises the risk of cardiovascular and neurological disorders in adult life and may be linked to low intake of animal and dairy products, researchers have said.

The study, India's largest paediatric assessment relating to this micronutrient, analysed vitamin B12 levels in 2,403 children, aged between 11 and 17, across a range of socio-economic groups. It found a deficiency prevalence of 32.4 per cent, with the deficiency levels higher among overweight and obese children. (See chart)

Earlier studies of vitamin B12 in adolescents had looked at no more than a few hundred samples.

"Our findings reinforce concerns that a chubby child isn't necessarily a healthy child," said Dwaipayan Bharadwaj, JNU professor and a scientist at the Institute of Genomics and Integrative Biology, New Delhi. Over half of obese adolescents had vitamin B12 deficiency.

Bharadwaj and his colleagues from the All India Institute of Medical Sciences, New Delhi, set out to explore how food habits might influence vitamin B12 levels in adolescents. Humans get this vitamin primarily from food such as meat, poultry, fish, eggs and dairy products, as well as from bacteria that synthesise the vitamin in the human gut.

Nutritionist Mansi Chopra questioned the adolescents about their food and beverage consumption on two days of the week.

"The consumption of energy-rich and nutrient-poor diet lacking in adequate intake of animal or dairy products might explain these findings," said Shraddha Chakraborty, a research scholar at the IGIB and the first author of the paper. "Boys appear to have lower B12 intake than girls."

The researchers said the prevalence of vegetarianism may mean that food fortification might be a cost-effective, practical strategy to combat this deficiency.

While some cereals, including breakfast cereals, are already fortified, the researchers have highlighted that such fortification is not yet mandatory.

The researchers found a higher prevalence of vitamin B12 deficiency in rural adolescents than their urban counterparts, and in boys than in girls. The study's findings appeared on Saturday in the Journal of Human Nutrition and Dietetics.

Studies have associated vitamin B12 deficiency with an increased risk of illness and premature death from cardiovascular diseases. "We're flagging a concern - a third of our adolescent children may be at future risk of cardiovascular disorders," said Nikhil Tandon, professor and head of endocrinology at AIIMS.

The researchers say their findings should encourage studies in other states to determine vitamin B12 levels in adolescents.

Multiple studies have indicated that treating vitamin B12 deficiency can reduce the risk of stroke.

"B12 deficiency is common, being present in 10 to 40 per cent of the population, is frequently missed, is easily treated and contributes importantly to cognitive decline and stroke in older people," J. David Spence, professor of neurology at the Robarts Research Institute in Canada, had written in a paper two years ago.