Issue 210 Item 8 Vitamin C Reduces Risk of Gestational Diabetes

Low maternal dietary intake of vitamin C and low maternal plasma ascorbic acid (AA) concentrations are associated with an increased risk of gestational diabetes mellitus (GDM). According to Cuilin Zhang, MD, PhD, of the Department of Epidemiology, University of Washington School of Public Health and Community Medicine, Seattle, United States, and colleagues, the role of dietary factors in the etiology of GDM has received little attention, although vitamin C has been implicated in the etiology of type 2 diabetes in nonpregnant women and men.

To determine whether low dietary intake of vitamin C and low plasma AA concentrations in pregnant women are associated with an increased risk of GDM, the researchers performed a study in 67 women with GDM meeting National Diabetes Data Group criteria and 260 controls.

Dietary vitamin C consumption during the periconceptional period and pregnancy was assessed using a 121-item validated, semiquantitative food frequency questionnaire, and maternal plasma AA concentrations were determined from blood samples collected during the intrapartum period.

Analysis showed that GDM cases tended to be older and heavier, with a 10% lower reported daily dietary vitamin C intake and 31% lower plasma AA concentrations compared with controls (130.7 ± 10.2 vs. 145 ± 4.9 mg/d, P = .190; 36 ± 2.0 vs. 53 ± 1.0 µmol/L, P < .001, respectively).

Additionally, after adjusting for confounding factors, the investigators found that women reporting daily vitamin C intake of less than 70 mg had a 3.7-fold increased risk of developing GDM (odds ratio [OR] = 3.7, 95% confidence interval [CI] 1.7-8.2).

Moreover, a linear trend was observed in risk of GDM with decreasing concentrations of plasma AA (P < .001), with women in the lowest quartile (< 42.6 µmol/L) experiencing a more than 12-fold increased risk of GDM (OR = 12.8, 95% CI 3.5-46.2) as compared with women in the highest quartile (> 63.3 µmol/L).

The researchers say that although a potential beneficial role of vitamin C was suggested by the study results, large, prospective, cohort studies are needed to evaluate glucose tolerance in pregnancy.

"Until such results are available, pregnant women may well benefit from following the current recommendations from the Department of Health and Human Services, which encourage consumption of fruits and vegetables that are important sources of vitamin C and other antioxidants," they concluded.
J Reprod Med 2004 Apr;49:4:257-66

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