To investigate the intake of iodine in mother-infant pairs.

An exploratory, cross-sectional study. Iodine intake was estimated using Nutritics nutritional analysis software, following 24-hour dietary recall. Iodine-rich foods were grouped and compared between those women who met the UK RNI for iodine (140 µg/day) and those who did not.

Online and telephone questionnaires.

Self-selecting caregivers of infants aged 6-12 months.

Ninety-one mother-infant pairs with a mean (SD) age of 33.2 (4.1) years and 8.4 (1.3) months, respectively, were included. Most mothers were exclusively breast feeding (54.9%). The estimated maternal median iodine intake from food and supplements (median 140.3 µg/day, just meeting the UK RNI for women of reproductive age, but not the WHO or BDA recommendations for lactating women (250 µg/day and 200 µg/day, respectively). Forty-six (50.5%) of mothers met the UK RNI. Estimated intakes of fish, eggs, cow’s milk, and yoghurt/cream/dairy desserts were significantly greater, whilst intakes of plant-based milk alternative drinks were significantly less in mothers who met the RNI for iodine (P<0.05) compared with those who did not. Infant iodine intake from food was positively correlated with maternal; total iodine intake, iodine intake from all food, and iodine intake from dairy foods (Spearman’s rho=0.243, 0.238, 0.264 respectively; P<0.05).

Women in the UK may not consume enough iodine to meet the demands of lactation. Guidance on iodine-containing foods, focussed on intake before and during pregnancy and lactation, and mandatory fortification of plant-based milk-alternatives could all serve to avoid deficiency.