Changes between diet quality and health-related quality of life (HR-QoL) over 12 years were examined in men and women, in 2844 adults (46 % males; mean age 47·3 (sd 9·7) years) from the Australian Diabetes, Obesity and Lifestyle study with data at baseline, 5 and 12 years. Dietary intake was assessed with a seventy-four-item FFQ. Diet quality was estimated with the Dietary Guideline Index, Mediterranean-Dietary Approaches to Stop Hypertension Diet Intervention for Neurological Delay Index (MIND) and Dietary Inflammatory Index. HR-QoL in terms of global, physical component summary (PCS) and mental component summary (MCS) was assessed with the Short-Form Health Survey-36. Fixed effects regression models adjusted for confounders were performed. Mean MCS increased from baseline (49·0, sd 9·3) to year 12 (50·7, sd 9·1), whereas mean PCS decreased from baseline (51·7, sd 7·4) to year 12 (49·5, sd 8·6). For the total sample, an improvement in MIND was associated with an improvement in global QoL (β = 0·28, 95 % CI (0·007, 0·55)). In men, an improvement in MIND was associated with an improvement in global QoL (β = 0·28, 95 % CI (0·0004, 0·55)). In women, improvement in MIND was associated with improvements in global QoL (β = 0·62 95 % CI (0·38, 0·85)), MCS (β = 0·75, 95 % CI (0·29, 1·22)) and PCS (β = 0·75, 95 % CI (0·29, 1·22)). Positive changes in diet quality were associated with broad improvements in HR-QoL, and most benefits were observed in women when compared to men. These findings support the need for strategies to assist the population in consuming healthy dietary patterns to lead to improvements in HR-QoL.

Pregnant women who are overweight/obese are particularly vulnerable to vitamin D insufficiency owing to higher physiological requirements and lower status (25(OH)D concentrations) associated with obesity. Achieving adequate maternal vitamin D status with current recommendations (10μg/d) remains controversial.

This study examined supplementation effects (10μg-vs-20μg vitamin D3/d) throughout pregnancy (12 weeks gestation until delivery) on vitamin D status of normal weight, overweight and obese pregnant women and on cord blood, using a double-blind randomised vitamin D intervention study (MO-VITD). 240 pregnant women were recruited throughout the year at antenatal clinics in Northern Ireland (equal numbers of normal weight (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2), and obese (> 30kg/m2)). Non-fasting maternal blood samples were collected at 12, 28 and 34–36 weeks gestation and from the umbilical cord after delivery and analysed for total serum 25(OH)D using LCMS.

A high prevalence of vitamin D insufficiency (25–50nmol/L) was found in the 1st trimester in both treatment groups (41.5% and 48.8%; 10μg vs. 20μg respectively). Maternal 25(OH)D concentrations increased from the 1st to 3rd trimester in both the 10μg/d and 20μg/d groups, with a higher increase in the 20μg group (17.1 ± 24.7 and 28.8 ± 33.3nmol/L, P = 0.002). There was no difference in cord blood 25(OH)D concentrations between treatment groups.

Women who started pregnancy with insufficient 25(OH)D concentrations remained insufficient throughout pregnancy in the 10μg/d group (49.9 ± 28.2nmol/L at trimester 3). In the 20μg/d group, women starting pregnancy as insufficient achieved levels of sufficiency in the 2nd (58.9 ± 30.6nmol/L) and 3rd (64.0 ± 35.9nmol/L) trimesters. Women who started pregnancy with sufficient vitamin D status (25(OH)D > 50nmol/L), maintained levels of sufficiency throughout pregnancy irrespective of treatment group (83.1 ± 24.4 and 96.7 ± 30.7 at trimester 3 in 10μg/d and 20 μg/d groups respectively); findings were similar across all BMI categories.

Obese women who started pregnancy with an insufficient status were found to have deficient cord blood (25(OH)D < 25 nmol/L) in both the 10μg/d and 20μg/d groups (19.4 ± 20.2 vs. 19.5 ± 9.4nmol/L respectively), whilst obese women who started pregnancy with sufficient status (> 50nmol/L) had cord blood concentrations considered insufficient (40.2 ± 18.4 vs. 44.2 ± 15.6nmol/L; 10μg vs. 20μg groups respectively).

Based on our findings of the high prevalence of vitamin D insufficiency in early pregnancy, maternal vitamin D supplementation of 20μg/d is advisable to maintain maternal vitamin D status in pregnant women in Northern Ireland.

Maternal BMI has been shown to be inversely correlated with vitamin D status (25-hydroxyvitamin D (25(OH)D) concentrations) during pregnancy. Pregnant women with obesity and with vitamin D deficiency are at risk of many adverse health outcomes in pregnancy.

The aim of this study was to examine differences in maternal vitamin D status across normal weight, overweight and obese pregnant women in early pregnancy.

Data collected at baseline from a double-blind randomised vitamin D intervention study (MO-VITD) were used. Pregnant women without pregnancy complications, aged > 18 years and having a singleton pregnancy were recruited between January 2016 and August 2017 at antenatal clinics in the Western Health and Social Care Trust, Northern Ireland. Non-fasting blood samples were collected at 12 weeks gestation and analysed for total serum 25(OH)D, using liquid chromatography tandem mass spectrometry. Data from 239 pregnant women (80 normal weight, 79 overweight, 80 obese) were included in the current analysis.

The mean ± SD 25(OH)D concentration of all pregnant women at 12 weeks gestation was 52.0 ± 21.6 nmol/L. Women classed as obese or overweight had significantly lower 25(OH)D concentrations compared to women of normal weight (48.8 ± 20.3 vs 49.8 ± 20.4 vs. 57.5 ± 23.1 nmol/L, P = 0.019; obese, overweight, normal weight respectively). A total of 45% of all pregnant women were found to be either vitamin D deficient (25(OH)D < 25nmol/L; 13%) or insufficient (25–50 nmol/L; 32%) in early pregnancy. BMI was significantly negatively correlated with 25(OH)D concentrations (r = -0.168; P = 0.009). Regression analyses showed that BMI (β = -0.165; P = 0.006), season (β = 0.220; P = < 0.0001), supplement use (β = -0.268; P < 0.0001) and a sun holiday within the previous 6 months (β = -0.180; P = 0.010) were significant predictors of 25(OH)D concentrations. In early pregnancy, 62% of pregnant women reported using a supplement containing vitamin D and 38% reported no supplement use. Supplement users had a significantly higher vitamin D status than non-supplement users in all BMI categories but overall, 37% of supplement users were still classified as vitamin D insufficient. Vitamin D status was significantly lower in winter months compared to summer months. In early pregnancy, especially during winter months, pregnant women with obesity, particularly non-supplement users, are at higher risk of low vitamin D status. Based on the lower vitamin D status observed in early pregnancy in obese women, the effect of BMI on vitamin D supplementation throughout pregnancy needs to be examined.