Prevalence and Predictors of Low Breast Milk Iodine Concentration in Women Following Vegan, Vegetarian, and Omnivore Diets.

Breast milk iodine concentration (BMIC) from vegan and vegetarian lactating mothers has not previously been evaluated. The goal of this study was to assess BMIC from vegans, vegetarians, and omnivores and to assess intake of iodine by breastfed infants. Breast milk samples from vegans ( = 12), vegetarians ( = 6), and omnivores ( = 12) living in the United States were analyzed. BMIC was determined at the mass-to-charge ratio () 127 by inductively coupled plasma mass spectrometry (ICP-MS) using an Agilent 8800 ICP-MS/MS (Agilent Technologies). There was a significant difference in mean BMIC between participants following a plant-based diet (vegan and vegetarian,  = 18) compared with omnivores [4.42 versus 5.02 Ln(BMIC), respectively;  = 0.0405]. In linear regression to predict BMIC, vegan diet was a negative predictor (standardized  = -0.409) and use of multi- or prenatal supplements was a positive predictor (standardized  = 0.319). There were differences in the percentage of inadequate BMIC per maternal diet (75% vegan, 67% vegetarian, omnivore 58%) but this did not reach statistical significance. In 67% of the samples (20/30) BMIC was lower than the National Academy of Medicine's adequate intake (AI), assuming infant milk consumption of 0.78 L/day. Most samples from vegans and vegetarians contained a lower BMIC than AI for infants 0-6 months. Counseling of pregnant vegans and vegetarians should highlight importance of iodine supplementation during lactation. The findings are based on a small number of samples, especially for vegetarians, and thus, they need to be confirmed by larger studies.