Table 4.
Assessment of dietary iodine intake for vegans, vegetarians and omnivores in included studies
| Study, year | Assessment of dietary iodine | Criteria for iodine intake | Dietary group | Dietary iodine intake (µg/d) | Contribution of iodised salt, seaweed, and iodine-containing supplements | Meeting criteria (Y/N)‡ | National salt fortification status | National iodine intake from the Global Scorecard of Iodine Nutrition (2021) | ||
|---|---|---|---|---|---|---|---|---|---|---|
| N | Female, male | Median/Mean | Q1 –Q3/sd | |||||||
| Abraham et al. 2022(53) | 3-d weighed food diaries | D-A-CH reference values: F:150 µg/d, M:180 µg/d | Strict raw 16 | 5, 11 | F: 49·6 | 37·4–64·6* | Twelve participants (75 %) recorded intake of dietary supplements (B12 and vitamin D). The consumption of iodine-containing supplements and iodised salt was not stated. Only individuals in the strict raw diet group consumed seaweed, but the contribution to iodine was not discussed. | N | Voluntary | Insufficient |
| M: 78·9 | 51·7–106·0* | |||||||||
| Vegan 32 | 18, 14 | F: 74·8 | 48·9–124·6* | N | ||||||
| M: 88·0 | 41·6–104·5* | |||||||||
| Omnivore 27 | 14, 13 | F: 100·5 | 76·5–142·6* | N | ||||||
| M: 165·9 | 106·2–181·5* | |||||||||
| Blaurock et al. 2021(54) | Self-administered, online 157 -item FFQ as part of the eNutri2019-DE web application analysed by Bundeslebensmittelschlüssel, BLS database | Dietary reference values (DRV) Germany 200 µg/d (18–51 years) | Vegetarian 31 | 31, 0 | F: 116·7 | 92–164* | Seventy-four percent of vegetarians and 63 % of omnivores reported consuming dietary supplements. The consumption of iodine-containing supplements, iodised salt and seaweed was not stated. | N | Voluntary | Insufficient |
| Omnivore 30 | 30, 0 | F: 108·6 | 75–144* | N | ||||||
| Eveleigh et al. 2022(34) | Online iodine-specific 45-item FFQ and 3-d food diaries analysed by a dietary software program, Nutritics | Reference Nutrient Intake (RNI) for UK 140 µg/d | Vegan (2016–17) FFQ: 12 FD: 10 |
FFQ: 107·0 | 88·0–131·5* | Multivitamins containing iodine were consumed by 12 % of participants providing an average of 140 µg/d to dietary iodine. Multivitamin supplements provided significantly greater iodine to the diets of vegans compared with omnivores and vegetarians (P = < 0·001 and P = 0·033, respectively). Seaweed supplements kelp and/or kombu were consumed by two omnivores in 2019, providing an average iodine intake estimate of 1541 µg/d. Seaweed supplied a significantly greater iodine contribution to the diets of vegans compared with omnivores (P = 0·040). One omnivore in 2016–17 recorded consuming iodised salt contributing 61 % of dietary iodine. |
FFQ: N Food diaries: N |
None | Adequate | |
| Food diaries: 47·6 | 29·6–61·8* | |||||||||
| Vegetarian (2016–17) FFQ: 5 FD: 4 |
FFQ: 202·9 | 176·5–291·7* | FFQ: Y Food diaries: N |
|||||||
| Food diaries: 68·8 | 55·8–90·4* | |||||||||
| Omnivore (2016–17) FFQ: 34 FD: 27 |
FFQ: 299·6 | 147·2–291·7* | FFQ: Y Food diaries: N |
|||||||
| Food diaries: 111·9 | 85·4–145·6* | |||||||||
| Vegan (2019) FFQ: 7 FD: 4 |
FFQ: 124·9 | 99·3–277·0* | FFQ: N Food diaries: N |
|||||||
| Food diaries: 17·3 | 17·2–21·4* | |||||||||
| Vegetarian (2019) FFQ: 9 FD: 6 |
FFQ: 230·0 | 122·0–363·4* | FFQ: Y Food diaries: N |
|||||||
| Food diaries: 71·4 | 55·7–82·8* | |||||||||
| Omnivore (2019) FFQ: 19 FD: 11 |
FFQ: 221·9 | 157·9–393·7* | FFQ: Y Food diaries: N |
|||||||
| Food diaries: 126·0 | 108·5–233·8* | |||||||||
| Fallon and Dillon, 2020(33) | 4-d food diaries analysed by a dietary software program, Nutritics | RNI for UK 140 µg/d and DRV 150 µg/d. | Vegan 20 | (20, 0) | F: 24·4 | 12·7† | Seaweed, salt or supplements not measured. | N | None | Adequate |
| Vegetarian 16 | (16, 0) | F: 90·8 | 55·9† | N | ||||||
| Omnivore 26 | (26, 0) | F: 112·6 | 62·1† | N | ||||||
| García-Morant et al. 2020(55) | Online 24-h food recalls analysed by a dietary software program, DIAL and data from the Spanish Agency for Food Safety and Nutrition National Dietary Intake Survey | None provided | Vegan 102 | (67, 35) | F: 79·0 | 76·0† | Dietary supplements were recorded and combined with dietary intake data. Seaweed and iodised salt not measured. | N | Voluntary | Adequate |
| M: 64·0 | 42·0† | |||||||||
| Omnivore 3321 | (1589, 1732) | F: 100·0 | 50·0† | N | ||||||
| M: 85·0 | 47·0† | |||||||||
| Groufh-Jacobsen et al. 2020(50) | 24-h food recalls and thirty-two-item FFQ updated from the Norwegian Food Composition Table 2019 | Estimated Average Requirement (EAR) of 100 µg/d | Vegan 115 | (74, 41) | 24-h recall: 92·0 | 19·0, 171·0* | The median contribution of supplements to iodine intake of 24-h recalls were 150 µg/d for vegans (n 57), vegetarians (n 25) and pescatarians (n 18). For FFQ, estimates supplements also contributed a median average of 150 µg/d to dietary iodine intake of vegans (n 69), vegetarians (n 26) and pescatarians (n 10). Seaweed (microalgae) provided 865 µg/d (364, 1978) to vegans (n 23), 843 µg/d (705, 1590) to vegetarians (n 8) and 375 µg/d (110, 610) to pescatarians (n 4). Iodised salt not measured. | 24-h recall: N FFQ: Y |
Voluntary | Insufficient |
| FFQ: 315·0 | 19·0, 361·0* | |||||||||
| Vegetarian 55 | (43, 12) | 24-h recall: 70·0 | 17·0, 165·0* | 24-h recall: N FFQ: Y |
||||||
| FFQ: 843·0 | 705·0, 1590·0* | |||||||||
| Pescatarian 35 | (31, 4) | 24 h: 123·0 | 16·0, 176·0* | 24-h recall: Y FFQ: Y |
||||||
| FFQ: 39·0 | 16·0, 324·0* | |||||||||
| Jakše et al. 2021(56) | 52-item FFQ analysed by a dietary software program, Open Platform for Clinical Nutrition (OPEN) | D-A-CH reference values, F:150 µg/d, M:180 µg/d | Vegan 51 | 34, 17 | 112·0 | 60·0† | Dietary supplements were recorded and combined with dietary intake data. Dietary supplements provided > 25 % of total iodine intake for vegans and omnivores (non-vegans) Seaweed and iodised salt not measured. | N | Mandatory | Adequate |
| Omnivore (non-vegan) 29 | 16, 13 | 96·0 | 58·0† | N | ||||||
| Kowalska et al. 2020(57) | Modelled diets were created by trained dieticians | EAR for Poland 95 ug/d | Vegan | 29·4 | 10·3† | Seaweed, salt, or supplements not measured. | N | Mandatory | Adequate | |
| Vegetarian (lacto-ovo) | 37·6 | 9·2† | N | |||||||
| Pescatarian | 39·2 | 11·1† | N | |||||||
| Omnivore (fish-free) | 46·9 | 20·32 | N | |||||||
| Omnivore (milk-free) | 62·8 | 46·42 | N | |||||||
| Omnivore (basic) | 57·9 | 19·1† | N | |||||||
| Omnivore (regular) | 87·2 | 45·0† | N | |||||||
| Whitbread et al. 2021(52) | 24-h diet food recalls by a smartphone app and food diaries analysed by a dietary software program, FoodWorks Dietary Analysis package | Recommended daily intake (RDI) 150 ug/d, EAR 100 ug/d and Nutrient Reference Values (NRV) for Australia and New Zealand (NHMRC) | Vegan 31 | 31, 0 | 78·0 | 62·0–91·0* | Participants who frequently consumed iodine-containing supplements were excluded. Six vegans reported ingesting seaweed (2·7 g/d), but iodine intake from seaweed was recorded as 0·0 ug/d. Iodised bread was the main iodised food source in vegans. Iodised salt was consumed by four vegan and four omnivore participants. | N | Mandatory | Adequate |
| Omnivore 26 | 26, 0 | 125·0 | 86·0–175·0* | N | ||||||
*
Median (Q1–Q3).
†
Mean ± sd.
‡
According to WHO criteria of 150 ug/d.