Vegans, Vegetarians and Pescatarians Are at Risk of Iodine Deficiency in Norway

Abstract

Low iodine intakes have been documented in different population groups in Norway. We aimed to assess iodine status, dietary intake, supplement and macroalgae use, and iodine knowledge in vegans, vegetarians and pescatarians. In this study, 115 vegans, 55 vegetarians and 35 pescatarians from the Oslo region of Norway, aged 18–60 years, participated. A spot urine sample was collected along with a dietary assessment of iodine intake, supplement and macroalgae use. The median urinary iodine concentration (MUIC) in vegans was 43 µg/L (moderate iodine deficiency), in vegetarians 67 µg/L and in pescatarians 96 µg/L (mild iodine deficiency). In multiple linear regression analysis, use of iodine supplements was one of the strongest predictors of UIC. About half of the participants had median 24-h iodine intakes below estimated average requirement (EAR) of 100 µg/day. Fifty percent had low knowledge score, while 27% had very low knowledge score. Vegans, vegetarians and possibly pescatarians in Norway, are unable to reach the recommended iodine intake merely from food and are dependent on iodine supplements. There is an urgent need for dietary guidance targeting vegans, vegetarians and pescatarians to avoid inadequate iodine intake in non-supplement users, as well as avoiding excess iodine intake in macroalgae users.

Prenatal and Postpartum Maternal Iodide Intake from Diet and Supplements, Urinary Iodine and Thyroid Hormone Concentrations in a Region of the United Kingdom with Mild-to-Moderate Iodine Deficiency

“…In terms of urinary iodine status, despite lower dietary intake, we reported higher UIC than women aged 19–64 in NDNS and similar UIC to that reported for their women of childbearing age, possibly because of the addition of iodide supplements for some women in pregnancy, while NDNS excluded pregnant and lactating women [ 15 ]. Our cohort also had higher UIC than some other studies of pregnant UK populations [ 21 , 36 , 37 ] but slightly lower than another using similar methods across three UK cities [ 11 ]. Whilst there appears to be some geographical variation, our results are consistent with other locations in the UK, and there is no evidence that results from our cohort are unrepresentative.…”

“…This may reflect the lack of any fortification or salt-iodization program in both the UK and Norway, in contrast to many other developed countries. The range of foods rich in iodide is limited to mostly seafood, dairy and eggs [ 20 ], so intakes may be particularly low amongst those following restricted or plant-based diets [ 21 , 22 ]. Without larger-scale monitoring programs, it is challenging to quantify iodine status in vulnerable sub-groups.…”

Iron Status of Vegans, Vegetarians and Pescatarians in Norway

“…From September to November 2019, we recruited 205 healthy participants—115 vegans, 55 vegetarians and 35 pescatarians—from the Oslo and Viken area in Norway. The primary endpoint of the study was iodine and B12 status [ 38 ]; however, we were also able to measure iron status. The participants were recruited through social media with convenience sampling and snowball sampling methods.…”

“…Participants who reported use of thyroid medication or consumption of meat-based products were excluded. For more detailed information, see the previously published study on iodine status in vegans, vegetarians and pescatarians [ 38 ]. Additionally, participants who had missing biomarkers of S-Fe were excluded from all descriptive analyses ( n = 14).…”

Reflection of Dietary Iodine in the 24 h Urinary Iodine Concentration, Serum Iodine and Thyroglobulin as Biomarkers of Iodine Status: A Pilot Study

“…However, select populations are susceptible to insufficient iodine status due to geographical location, food intake practices, or increased iodine needs (e.g., pregnancy and lactation). Subpopulations at increased risk for low iodine intake include pregnant and lactating women [ 4 , 5 , 6 ], vegans [ 7 , 8 , 9 ] and vegetarians [ 7 , 8 , 9 , 10 , 11 ], those who avoid seafood and/or dairy [ 12 ], follow a sodium restricted diet [ 13 , 14 ], or eat local foods in regions with iodine-depleted soils [ 1 , 15 ]. The Institute of Medicine, American Heart Association, and the 2020–2025 Dietary Guidelines for Americans [ 16 ] have advocated for decreasing sodium intake to less than 2300 mg/day [ 17 ] and more prudently to less than 1500 mg/day [ 18 ], which could be reducing Americans’ intake of iodized salt.…”