Background: Recommended carbohydrate (CHO) consumption in pregnancy is <175g/day; however many women consume significantly lower amounts1. Beneficial effects on glycaemic control and pregnancy weight gain have been reported in women with gestational diabetes (GDM) following a reduced carbohydrate (CHO) diet2–4, but maternal and fetal outcomes, or micronutrient adequacy, remain uncertain5,6.
Aims: To explore whether adherence to a reduced CHO diet is improved, and micronutrient adequacy met, by the provision of weekly fruit and vegetables or food vouchers, for those with GDM.
Participants/methods: A randomised controlled trial recruited women with newly diagnosed GDM, to one of three interventions: i) provision of weekly fruit and vegetables, provided at no cost or ii) weekly supermarket vouchers or iii) supermarket vouchers to an equivalent value provided at the end of the study. Participants had weekly reviews with a dietitian. The primary outcome variable was CHO intake assessed by a food diary, at baseline, and at 36 weeks gestation. Secondary outcomes were the evaluation of micronutrient adequacy by food diaries.
Results: There were 20 participants recruited at a mean (SD) 30.9 (1.6) weeks gestation, age 34.7 (5.2) years, and pre-pregnancy BMI of 28.3 (5.8) kg/m2. There were no statistically significant differences in CHO or micronutrient intake between the three intervention groups. For all participants combined there was significant reduction in CHO intake at 36 weeks gestation, 136 (19) g/day compared to baseline, 165 (47) g/day; paired difference (95% CI) 29 (7.2 to 49.8), P=0.011. There was also a difference in sugar intake at 36 weeks gestation; 49 (14) g/day compared to baseline, 59 (23) g/day; paired difference 10 (0.06 to 20.7), P = 0.049. There were no significant differences in micronutrient, fibre, or energy intake at 36 weeks compared to baseline. The frequency of ketones remained unchanged during the intervention compared to baseline.
Conclusion: Providing fruit and vegetables at no cost did not increase adherence to a low CHO diet, compared to usual food provision. However, over all groups combined there was evidence of a 29 g/day reduction in CHO intake compared to baseline and an associated reduction in sugar intake of 10 g/day, with no detrimental effect on micronutrients. Dietitian support may be the most important factor to encourage women with GDM to successfully follow a low CHO diet.