Dietary factors and blood micronutrient levels as risk factors for gestational diabetes mellitus in India: The Bangalore Nutrition Gestational Diabetes Lifestyle Study (BANGLES)

Abstract

Indian women are at higher risk of gestational diabetes mellitus (GDM) than their Western counterparts. The current GDM prevalence in urban India is 20 – 25% of pregnancies. Observational evidence suggests a role for diet in GDM prevention, but data from India is sparse. My PhD project aimed to examine associations of peri-conceptional diet and early pregnancy blood micronutrient levels with GDM risk in Bangalore, India. In June 2016, I set up the BANGLES, a prospective observational study. Women (n=785) from low, middle and high-income groups were recruited at 5-16 weeks’ gestation. The exposures were recalled peri-conceptional diet retrospectively assessed at recruitment, using a Food Frequency Questionnaire (FFQ), and blood micronutrient levels in early pregnancy: plasma folate, vitamin B12, vitamin D and serum ferritin. Diet exposure was represented by the frequency of intake of food groups, and diet patterns derived using Principal Components Analysis (PCA). The outcome was GDM assessed by a 75-gram Oral Glucose Tolerance Test (OGTT) at 24-28 weeks’ gestation, and defined using WHO 2013 criteria. Associations between the exposures and GDM were analysed using multiple logistic regression, adjusting for potential confounders, with and without body mass index (BMI). Potential confounders adjusted for included the woman’s age, gravidity, history of poly cystic ovarian syndrome, family history of type 2 diabetes, urban/rural residence, nuclear/ joint family, physical activity, socio-economic status indicators and the use of synthetic nutrient supplements. GDM prevalence was 22%. Five distinct peri-conceptional diet patterns were derived in the PCA: 1) high-diversity, urban pattern, 2) rice-fried snacks-chicken-sweets pattern, 3) healthy, traditional vegetarian pattern, 4) snacks, sweets and takeaway pattern and 5) unpolished rice- vegetables-fish pattern. All except pattern 3 included a mixture of both healthy and unhealthy foods. There were no statistically significant associations between any of the food groups or diet patterns and GDM after adjusting for multiple testing. Higher BMI was a strong independent risk factor for GDM and adjusting for BMI weakened the diet pattern-GDM associations, suggesting that it may be a mediator of any diet pattern effects. Early pregnancy blood levels of folate, vitamins B12 and D were not associated with GDM risk. Women with low ferritin levels (<15 ng/ ml) had a lower GDM risk compared to women with normal serum ferritin levels (41- 400 ng/ml; aOR: 0.39, 95% CI: 0.17, 0.90, p=0.02). Women who used iron and calcium+vitamin D tablets (almost always prescribed together) during early pregnancy had a higher GDM risk (aOR: 1.91, 95% CI: 1.21, 3.01, p=0.005). Women’s physical activity (PA) during pregnancy was low overall, and not related to GDM. BANGLES is the first Indian prospective study to investigate associations of food groups, diet patterns, nutrient supplements and ferritin status with GDM. The findings support the existing global health recommendation to encourage women to attain a healthy pre-pregnancy BMI, which in turn requires a healthy diet and regular physical activity. My study did not identify specific foods or diet patterns associated with GDM that could form the basis of new recommendations. In future work I will explore healthy diet indices in relation to GDM in my data. The role of iron in the aetiology of GDM requires further research.

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ORCID for Caroline Fall: orcid.org/0000-0003-4402-5552

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