Low levels of vitamin B12 in pregnancy may harm the metabolic health of offspring, researchers suggest.
Senior author Dr. Ponusammy Saravanan, of the University of Warwick Medical School in the United Kingdom, and colleagues present their preliminary findings at this week's Society for Endocrinology annual conference in the U.K.
Vitamin B12 is a water-soluble vitamin naturally present in animal products, such as milk, eggs, cheese, meat, poultry, and fish. It is also available as a dietary supplement and added to some non-animal products, such as breakfast cereals.
The recommended daily vitamin B12 intake for individuals aged 14 and older is 2.4 micrograms, increasing slightly to 2.6 micrograms for expectant mothers, and 2.8 micrograms while breast-feeding.
Dr. Saravanan and colleagues say previous research has shown that women with low vitamin B12 levels during pregnancy are more likely to have a higher body mass index (BMI) and have low-birth-weight babies with high cholesterol.
Vitamin B12 deficiency in pregnancy may alter offspring's leptin levels
Dr. Saravanan and team set out to determine whether these previous observations might be associated with leptin, a hormone produced by fat cells. Often referred to as the "satiety hormone," leptin tells us when it is time to stop eating.
Research has shown that excess weight can cause an increase in leptin levels in response to food intake. This can cause leptin resistance, which may lead to further overeating, weight gain, and insulin resistance, increasing the risk of type 2 diabetes.
For their study, the researchers analyzed 91 blood samples taken from mothers and their offspring at delivery to determine vitamin B12 levels. Additionally, they analyzed 42 maternal and neonate fat tissue samples and 83 placental tissue samples.
The researchers found that children born to mothers with vitamin B12 deficiency - defined as less than 150 picomoles per liter - were more likely to have higher-than-normal leptin levels, which may raise their risk of type 2 diabetes and other metabolic disorders.
The team speculates that vitamin B12 deficiency in expectant mothers may affect leptin gene programming, altering production of the hormone during fetal development.
"The nutritional environment provided by the mother can permanently program the baby's health. We know that children born to under or overnourished mothers are at an increased risk of health problems such as type 2 diabetes, and we also see that maternal B12 deficiency may affect fat metabolism and contribute to this risk. This is why we decided to investigate leptin, the fat cell hormone."
Dr. Ponusammy Saravanan
At present, the researchers are unable to pinpoint the precise mechanisms by which maternal vitamin B12 deficiency increases leptin levels for offspring, but they do have some theories.
"Either low B12 drives fat accumulation in the fetus, and this leads to increased leptin, or the low B12 actually causes chemical changes in the placental genes that produce leptin, making more of the hormone," says study co-author Dr. Adaikala Antonysunil, also of the University of Warwick.
"As B12 is involved in methylation reactions in the body which can affect whether genes are turned on and off, we suspect it may be the latter," he adds.
With further study, the researchers hope to prove their suspicion true. If their findings are confirmed, the team says the current recommendations for vitamin B12 during pregnancy may need to be reviewed.