Iodine and goitrogen intakes in UK pregnant women; relationship with dietary sources and iodine status

The recommended intake of iodine during pregnancy is 250 μg/day (1) . The shift towards sustainable, plant-based diets (PBDs) is increasing, especially among women of childbearing age (2) . PBDs have low iodine content, and some plant sources, such as cruciferous vegetables and soy-based products, contain goitrogens that reduce iodine absorption, potentially increasing the risk of iodine deficiency (ID) (2) . We aim to describe the iodine and goitrogen intake in a cohort of pregnant women and explore the contributors and correlations with dietary food sources, urinary iodine-to-creatinine ratio and socioeconomic status. Using the Avon Longitudinal Study of Parents and Children (ALSPAC), women were selected based on a singleton pregnancy and the availability of iodine-intake data, assessed using a validated food frequency questionnaire (FFQ) at 32 weeks gestation (n=11748). Descriptives analyses and non-parametric tests were used to describe iodine and goitrogen-rich food intakes. Spearman correlations were used to explore relationships with the iodine-to-creatinine ratio (n=3971, median 13 weeks gestation, IQR 9-18), food sources, and socioeconomic status in unadjusted models. Median maternal iodine intake at 145 μg/d (IQR 114-177) was low compared to the WHO intake recommendation for pregnancy (1) . Median iodine-to-creatinine ratio was also low at (131 μg/g, IQR 87-213). Iodine intake was positively associated with the iodine-to-creatine ratio (rs=0.122, P <0.001). Median intake of goitrogen-rich foods was 55 g/day (IQR 32-69g). Women with iodine intake below 250 μg/d were more likely to have a lower intake of goitrogen-rich foods (P <0.001). Iodine intake was positively associated with daily intake of milk (rs=0.601, P <0.001), dairy/egg (rs=0.398, P <0.001), seafood (rs 0.636 P <0.001), fruit and vegetables (rs=0.331, P <0.001) and goitrogen intake (rs 0.230, P <0.001), with milk contributing to 38% of iodine intake. Green vegetables and cabbage contributed 43% of goitrogen-rich food intake. Women with a degree had higher intake of iodine (p < 0.001) and goitrogen-rich foods (p < 0.001) compared to those without a degree. There was no association between intake of goitrogen-rich foods and the iodine-to-creatinine ratio (rs = 0.017, P=0.277). In line with previous research on iodine status in the UK (3 ), iodine intake was also inadequate in this cohort of UK pregnant women. Iodine intake was positively associated with urinary iodine-to-creatinine ratio, iodine- and goitrogen-rich foods, and socioeconomic status. Further research is required due to the sparsity of data on the goitrogenic potential of PBDs and the influence on child neurodevelopment. This study highlights the need for continued monitoring of iodine intake in pregnant women, especially those adhering to PBDs.