Women who eat lots of foods that tend to make blood sugar soar may be more likely to have a baby with birth defects of the brain or spine, a new study from the California Birth Defects Monitoring Program in Berkeley suggests.
These foods, known as high glycemic index foods, include white bread and other highly processed grains, potatoes and soft drinks. Researchers say the finding, seen predominantly among obese women in the study, adds to evidence that a problem in blood-sugar control might be involved in neural tube defects.
Neural tube defects such as spina bifida arise in the first several weeks of pregnancy, when the brain and spine are beginning to take shape. One nutritional factor in this early period, a woman's intake of the B vitamin folic acid, is known to affect the risk of these birth defects. But there is also evidence that a mother's obesity or diabetes might raise the risk of neural tube defects, suggesting a role for maternal blood sugar levels.
Among more than 900 California women in the new study, those who ate more foods with a high glycemic index around the time of conception had a higher risk of having a baby with a neural tube defect. The link was strongest for obese women; those who ate the most high glycemic index foods had four times the risk of having an affected baby as obese women who ate the fewest.
The glycemic index measures how strongly and quickly blood sugar rises after a person eats carbohydrate-containing food. The sugars in foods with a high index are quickly digested and absorbed, creating a surge in blood sugar levels. In contrast, the carbohydrates in foods like fiber-rich whole grains, beans, fruits, vegetables, and some dairy products typically cause a slower release of sugar into the blood.
Researchers still don't fully understand the roots of neural tube defects, and said it is studies like this one that "provide the puzzle pieces one by one to assemble the causal picture."
The scientists stressed that eating a balanced diet with enough folic acid remains the best advice for cutting the risk of neural tube defects. Foods rich in the vitamin include lentils, leafy greens like spinach, and orange juice.
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