Effect of dietary fiber on the oral glucose tolerance test in pregnancy

Abstract

Paired oral glucose tolerance tests (GTTs) were performed during the third trimester of pregnancy to determine whether soluble fiber, which is known to blunt the rise in postprandial serum glucose in nonpregnant subjects, demonstrated similar effects in pregnancy. Normal pregnant women (n = 14) and gestational diabetic patients (n = 4) were first given a standard 100 gm oral GTT, and serum levels of glucose and insulin were determined in the fasting state and at 60, 120, and 180 minutes after ingestion of the glucose load. Several days later, a second GTT was done. In this test, glucose was combined with 15 gm of guar gum, a purified soluble dietary fiber. Improved glucose tolerance was documented in all but one patient. Guar gum produced a significant reduction in mean serum glucose levels at 1 hour (p < 0.005), 2 hours (p < 0.005), and 3 hours (p < 0.005), and each of the four gestational diabetic patients tested showed a normal glucose tolerance curve. The soluble dietary fiber, guar gum, did limit the postchallenge rise in serum glucose in pregnant subjects. Furthermore, the improvement in glucose tolerance in gestational diabetic patients is sufficient to suggest a potential clinical value for dietary fiber in the treatment of gestational diabetes.