Neural tube defects are a common birth defect that are characterised by an opening in the spinal cord or brain which results from a failure of the neural tube to properly seal following the third week of pregnancy. A number of nutritional factors are known to influence the risk of a neural tube defects forming, the most well known of these being a deficiency of folic acid. However, low intakes of zinc, methionine, vitamin C and dairy products are also associated with increased risk of a neural tube defect. Interestingly, a number of factors relating to carbohydrate metabolism, such a diabetes, hyperinsulinaemia, high intakes of sweets and obesity also increase the risk of neural tube defects. The link between neural tube defects and defects in carbohydrate metabolism and high sugar intakes suggests that poor glycaemic control may be particularly detrimental during pregnancy.
Resaecrhers1 have investigated the associations between pre-pregnancy intakes of fructose, glucose and sucrose, as well as foods with high glycaemic indexes, with the risk of offspring developing neural tube defects. Interviews with mothers of 454 neural tube defect affected pregnancies were performed in hospitals in California and compared to information taken from interviews with 462 mothers of non-affected pregnancies. The results showed that high intakes of sucrose and foods with high glycaemic indexes increased the risk of a neural tube defect pregnancy roughly 2 fold. The risk associated with sucrose was independent of the pre-conception folic acid status of the mother. Women with a body mass index of over 28 kg/m2 had a roughly 4 fold increase in the risk of a pregnancy with a neural tube defect if they ate foods with high glycaemic indexes.
Mainstream perceptions regarding neural tube defects focus almost entirely on folic acid, however there is good evidence to suggest that other factors require equal attention. Interestingly, in this study high intakes of glucose and fructose alone where not associated with an increased risk of a pregnancy affected by a neural tube defect, but combined as sucrose the association became significant. The effects of high glycaemic foods on the neural tube may result from the fact that in the early weeks of gestation the developing foetus dies not have working β cell function and so hypoglycaemia and hyperglycaemia from the mother may lead to a lack or excess of glucose supplied to the developing foetus. Sucrose has a low glycaemic index but is known to lead to insulin resistance which is a leading cause of poor blood sugar control.
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