Research review 192
Cross-sectional study with laboratory analyses and dietary assessment
Short answer
In an Oslo study, 76% of 175 breastfeeding women had breast milk iodine concentrations below 100 micrograms per litre. The median was 68 micrograms per litre. The researchers also found that iodine intake was often below recommended levels in this sample. These are measurements in a specific group, not clinical diagnoses in 76% of the participants.
What did the researchers investigate?
In 2016, five mother and child health centres in Oslo were randomly selected. Women breastfeeding between two and 28 weeks postpartum were invited to participate. Each of the 175 women provided four breast milk samples, combined into one sample per participant and analysed for iodine. Researchers assessed food and supplement intake over the preceding 24 hours and habitual diet.
What did they find?
The median breast milk iodine concentration was 68 micrograms per litre, meaning half the samples were above and half below that value. In 76% of samples, the concentration was below 100 micrograms per litre. Only 19% reported taking an iodine-containing supplement in the previous 24 hours. Median estimated iodine intake from food was 121 micrograms during that day, rising to 134 micrograms per day when supplements were included. The findings indicate low iodine intake in the study population.
How certain can we be?
Laboratory testing provides direct measurements, but dietary information relied in part on self-report. Participants came from five health centres in Oslo, and their findings cannot represent all breastfeeding women in Norway. Breast milk iodine measurements help assess population nutrition. One value does not establish an individual clinical diagnosis of iodine deficiency.
Who do the findings apply to?
175 breastfeeding women between two and 28 weeks after childbirth, recruited at five Oslo health centres in 2016.
What might this mean in everyday life?
Iodine is essential for thyroid hormone production. Breastfed babies receive iodine through breast milk. Diets low in milk, dairy foods and white fish may result in low iodine intake. Healthcare professionals can help assess diet and supplement needs. Excess iodine can also be harmful, so supplements should be tailored. Read about postpartum nutrition.
What do we still need to know?
More recent representative surveys of iodine intake and breast milk iodine are needed, alongside information on changes throughout breastfeeding and the effectiveness of targeted dietary measures.
Sources
Original publication: Henjum S et al. Suboptimal Iodine Concentration in Breastmilk and Inadequate Iodine Intake among Lactating Women in Norway. Nutrients. 2017;9(7):643. DOI: 10.3390/nu9070643.
Original study published: 22 June 2017. Source checked: 9 November 2026.
This review is based on what the researchers themselves report about methods, results and limitations.