Assessment of nutritional biomarkers in pregnant women and associations with gestational diabetes

Abstract

Background: Gestational diabetes mellitus (GDM) is one of the most common complications diagnosed in pregnancy and is associated with several adverse outcomes for mothers and their offspring. Several factors, both genetic and environmental, are thought to affect a person’s risk of being diagnosed with GDM. Increased age, overweight and obesity, sedentary lifestyle, a previous history of GDM or giving birth to a child with macrosomia and family history of diabetes are among known risk factors. Recent studies have indicated that diet can also affect GDM risk, regardless of a women’s body mass index (BMI) and other known risk factors. Aim: This PhD thesis aimed to (a) examine dietary intake and nutritional status in early pregnancy by means of a subjective diet screening questionnaire as well as objective biomarkers (papers I-IV) and (b) explore associations with gestational diabetes (papers I-III). Further aim was to compare results from the diet screening questionnaire to biomarker results (papers I-IV). Specifically, the aims were to: Determine the women´s intake of vitamin D, measure serum 25-hydroxyvitamin (25OHD) and investigate associations to risk of GDM diagnosis. Investigate associations between early pregnancy whole grain intake, with the use of a whole grain biomarker and diet screening questionnaire and explore associations to GDM diagnoses later in pregnancy. Determine dietary intake as well as plasma fatty acid profiles in early pregnancy and assess associations to later GDM diagnoses. Compare results of the diet screening questionnaire to those derived from biomarkers of consumption. Methods: Subjects were women attending ultrasound screening at the Ultrasound Department at Landspitali - National University Hospital in their 11th to 14th week of pregnancy, from October 20178 to March 2018. During their visits, the women answered a diet screening questionnaire as well as questions regarding age, height, weight and background in addition to providing blood and spot urine samples. The samples were analysed for concentrations of plasma fatty acids, plasma alkylresorcinols (a biomarker for whole grain intake), and serum 25OHD. Data on weight and gestational diabetes diagnoses were later gathered from their medical records. Results: GDM was diagnosed in 127 women (14.9%). Only 14.9% of the women adhered to the recommendation of consuming two portions of whole grains daily (Paper II). The women’s median intake of lean fish was approximately once weekly, and their intake of fatty fish was approximately once monthly (Paper III). Approximately one-third of the cohort had S-25OHD concentrations below adequate levels (< 50 nmol/L) during the first trimester of pregnancy, thereof 5% had deficient concentrations (25OHD <30 nmol/L). However, no clear vi association was observed between S-25OHD and GDM (Paper I). Overall diet quality in early pregnancy appeared to be lower among the women later diagnosed with GDM (Paper III). The relative risk (RR) of being diagnosed with GDM was 50% (95% CI: 0.27, 0.90) lower among individuals in the highest quartile compared to those in the lowest quartile of plasma ARs (P-trend = 0.01) after adjusting for age, pre-pregnancy BMI≥25 kg/m2 , parity, education, smoking during pregnancy, and family history of diabetes. There was a significant dose-response relationship between AR levels and GDM risk (Paper II). The total concentration of fatty acids (FAs) was significantly higher in women diagnosed with GDM when compared to women without this diagnosis, as were the concentrations of all types of FA—except for long-chain n-3 fatty acids EPA+DHA. The mean adjusted difference for total FA between the women with and without GDM was 133 μg/mL (95% CI 33 to 233) (Paper III). There was a positive correlation between the women’s intake of all fish and total omega-3 supplements and the concentrations of plasma omega-3 FA (r=0.34 P <0.001). The women with a daily intake of cod liver oil or omega-3 oil supplements displayed higher concentrations of EPA and DHA compared to those who never used these supplements (median: 108 vs. 91 and 103 vs 90 μg/ml, respectively). A positive correlation was seen between reported intake of vitamin D supplements and S-25OHD concentrations (r=0.31 P <0.001), and higher reported frequency of whole grain intake was associated with a significant increase in plasma AR concentrations (Papers I-IV). Conclusion: These results indicate several opportunities to improve the diet and vitamin D status of pregnant women in Iceland. The women who were not diagnosed with GDM appear to have a slightly better adherence to dietary recommendations overall. The role of vitamin D was not as clear in this context. The associations of whole grain intake to GDM risk were established by measuring plasma AR concentration, something that has not been done previously in a pregnancy cohort. Our findings also indicate that the diet screening questionnaire used in our study, is a tool that can be used to estimate food consumption of selected food groups and intake of specific nutrients during pregnancy.