Pregnant women with combined low vitamin B12 and high folate levels showed a 97% increase in risk pregnancy-related diabetes, according to a study in Clinical Nutrition.
Gestational diabetes mellitus (GDM) is characterised by the development of diabetes during pregnancy, which had not been present previously. It generally occurs in the second or third trimester. GDM raises the risk of pregnancy complications, preeclampsia and premature birth. The child is also more prone to obesity and diabetes in later life.
Asian women, particularly Indian mothers-to-be, were found to be at greater risk of GDM if they had low blood levels of vitamin B12 combined with high folate.
“High folate concentrations coupled with vitamin B12 insufficiency were associated with higher odds of GDM,” wrote Jun S. Lai, lead author at the Singapore Institute for Clinical Sciences.
The researchers also emphasised the importance of the study findings. ”They highlight the need to carefully evaluate and manage folate and vitamin B12 status in pregnant women.”
Although adequate folate status is widely recognised as important during pregnancy, this study suggests that, in some ethnic groups, vitamin B12 status may also be important and raises a question on the safety of excess folate.
“Given the widespread vitamin B12 insufficiency in our sample (48%), this strongly suggests a need to consider shifting our attention to address this nutritional issue within the population particularly in Indian mothers and others at risk of vitamin B12 insufficiency,” commented the researchers.
The study population consisted of 913 pregnant women of Chinese, Malay and Indian ethnicities.
GDM was diagnosed by measuring blood sugar levels under fasting state and two hours after administration of oral glucose (postprandial conditions).
“We observed that higher folate concentrations during pregnancy were associated with higher postprandial glucose concentrations and higher odds of GDM,” wrote the researchers.
Higher folate levels were associated with a 29% increase in GDM risk over the study population, but an increase of 128% among Indian women.
The scientists also noted a 19% reduction of GDM risk in women with adequate vitamin B12 levels, “Higher vitamin B12 concentrations were associated with lower fasting and postprandial glucose concentrations and lower odds of GDM.”
The impact of having both low vitamin B12 and high folate levels was particularly dramatic, increasing GDM risk by 97%.
“Our results further demonstrated that the combination of vitamin B12 insufficiency and high folate concentrations was associated with higher GDM risk, suggesting that an imbalance in the two B-vitamins may be responsible for glucose intolerance,” the scientists hypothesised.
However, the scientists stressed the exact mechanism linking high folate, low B12 with glucose intolerance and insulin resistance remains unclear.
The trial “has potential implications for antenatal supplement recommendations but will require confirmation in future studies,” the team concluded.