Table 5.
Assessment of dietary iodine intake for vegans, vegetarians, and omnivores in industrialised countries.
| Study, Year | Assessment of Dietary Iodine | Criteria for Iodine Intake Used in Study | Dietary Group (N) (Male, Female) | Dietary Iodine Intake (µG Day−1) | Contribution of Iodised Salt, Seaweed, and Iodine-Containing Supplements | Meeting Criteria (Y/N) |
|---|---|---|---|---|---|---|
| Allès, 2017 [36] | Three repeated 24 h dietary records. | 150 µg day−1 RDI for the French population (2001) [52]. | Vegan (789) Vegetarian (2370) Omnivore (90,664) |
248.3 ± 9.8 (a) 1 222.6 ± 5.7 (a) 1 180.1 ± 1.1 (a) 1,** |
Seaweed, salt, or supplements not measured. | Y Y Y |
| Draper, 1993 [37] | Three-day weighted food diaries. Analysed using UK Ministry of Agriculture, Fisheries and Food data. | DRV of 140 µg day−1 Department of Health (1991) [53]. |
Vegan (38) (18,20) | M, 98.0 ± 42.0 2,** F, 66.0 ± 22.0 2,** |
95% used sea salt or seaweed. 30%–40% consumed food supplements containing seaweed 1–2 days a month. 15.6 µg day−1 provided by dietary supplements. |
N |
| Lacto-Vegetarian (52) (16,36) | M, 216.0 ± 73.0 2,** F, 167.0 ± 59.0 2,** |
No iodine provided by salt, seaweed or supplements. | Y | |||
| Demi-Vegetarian (35) (13,24) | M, 253.0 ± 164.0 2,** F, 172.0 ± 91.0 2,** |
No iodine provided by salt, seaweed or supplements. | Y | |||
| Kristensen, 2015 [49] | Four-day weighed food diary. | 150 µg day−1 NNR (2012) [54]. | Vegan (70) (33,37) | M, 64.0 (43.0–91.0) 3,** F, 65.0 (54.0–86.0) 3,** |
Salt not measured. Three vegans consumed seaweed. 9.0 µg day−1 (M) and 6.0 µg day−1 (F) was provided by dietary supplements. |
N |
| Omnivore (1257) (566,691) | M, 213.0 (180.0–269.0) 3 F, 178.0 (146.0–215.0) 3 |
Salt not measured. No iodine provided by seaweed. 107 µg day−1 (M) and 78.9 µg day−1 (F) was provided by dietary supplements. |
Y | |||
| Lightowler, 1998 [41] | Four-day weighed food diary with duplicate portion technique. | 140 mg day−1 RNI Department of Health (1991) [53]. | Vegan (30) (11,19) |
M, 138.0 ± 149.0 2 F, 187.0 ± 246.0 2 |
Salt not measured. Three vegans consumed seaweed, resulting in significantly higher iodine intake (p < 0.001) Seaweed consumers were over six times the RNI. Iodine-containing supplements were consumed by five (45%) males and seven females (37%). Providing 54.0 mg day−1 on average to the diet. |
M, N F, Y |
| Lightowler, 2002 [42] | Four -day food diaries with duplicate portion technique. Analysed using CompEat 4 software. |
140 mg day−1 RNI Department of Health (1991) [53]. | Vegan (26) (11,15) |
Diet Diary M, 42.0 ± 46.0 2 F, 1448.0 ± 3879.0 2 Duplicate Diary M, 137.0 ± 147.0 2 F, 216.0 ± 386.0 2 |
Salt not measured. Two vegans consumed seaweed, resulting in iodine intake to exceed the RNI. Dietary supplement intake was recorded but not included to dietary intake. |
Diet Diary M, N F, Y Duplicate DiaryM, N F, Y |
| Nebl, 2019 [43] | Three-day food diaries analysed by PROD16.4®. | 200 µg day−1 RV German, Austrian and Swiss Nutrition Societies (2019) [55] | Vegan (27) (10,17) |
57.7 (48.4, 67.0) 4,* | Salt or seaweed not measured. No iodine provided by supplements. |
N |
| Vegetarian (25) (10,15) | 61.6 (49.4, 73.7) 4,* | N | ||||
| Omnivore (27) (11,16) |
88.8 (64.1, 114.0) 4,** | N | ||||
| Rauma, 1994 [50] | Seven-day food diaries analysed by NUTRICA Finland. | 0.1–0.2 mg day−1 RDA (120–200 µg day−1) Committee on Dietary Allowances, Food and Nutrition Board, National Research Council (1989) [56]. |
Vegan (Living Food Diet) (9) | 29.0 ± 18.0 2 | One participant did not use iodised salt. 25% of daily iodine in vegans was provided by seaweed (estimated >8.0 µg day−1). Four vegans consumed seaweed, resulting in higher intake. |
N |
| Omnivore (8) | 222.0 ± 93.0 2 | Y | ||||
| Remer, 1999 [47] | Five-day dietary intervention of pre-selected food items representing each diet. Calculated using food tables. | NA | Vegetarian (Ovo-Vegetarian)(6) Omnivore (6) |
15.6 ± 21.0 2 35.2 ± 15.0 2 |
No iodized salt, seaweed or supplements were permitted during the study. All drinks including water were low in iodine and other minerals. | N N |
| Omnivore (High Protein) (6) | 44.5 ± 16.5 2 | N | ||||
| Waldmann, 2003 [46] | Pre-study questionnaire identifying regularly consumed foods. Two estimated nine-day FFQs using 7 days of records. |
200 mg day−1 RI, German Society of Nutrition (2000) [57] | Vegan (Strict) (98) (48,50) Vegan (Moderate) (56) (19,37) |
M, 87.7 ± 30.6 2 F, 82.1 ± 34.4 2 M, 93.7 ± 27.8 2 F, 78.1 ± 25.6 2 |
Salt not measured. Seaweed intake not measured. 46% of participants used some form of nutritional supplement. Iodine-specific supplements were not recorded. |
N N |
| Sobiecki, 2016 [45] | 112-item semi-quantitative FFQ. Analysed based on UK Ministry of Agriculture, Fisheries and Food data. |
150 µg day−1 RDA, dietary reference intakes for iodine (2001) [58] | Vegan (803) (269,534) |
M, 55.5 ± 40.0 2 F, 54.1 ± 40.0 2 Total, 58.5 (a) 2 |
Salt not measured. Two participants who consumed seaweed had values close to the maximum tolerable daily intake for iodine. Supplement intakes recorded did not specify iodine content. |
M, N F, Y (a), N |
| Vegetarian (6673) (1516,5157) |
M, 141.0 ± 77.4 2 F, 146.1 ± 78.8 2Total, 148.1 (a) 2 |
M, N F, N (a), N |
||||
| Pescatarian (4431) (782,3749) |
M, 197.4 ± 84.7 2 F, 194.8 ± 85.9 2 Total, 196.8 (a) 2 |
Y (a), Y |
||||
| Omnivore (Meat-Eaters) (18,244) (3798,14446) | M, 214.3 ± 85.6 2 F, 213.8 ± 85.2 2 Total, 212.2 (a) 2 |
Y (a), Y |
Abbreviations; RDI, Recommended Daily Intake; DRV, Daily Recommended Value; NNR, Nordic Nutrition Recommendations; RNI, Recommended Nutrient Intake; RV, Recommended Value; RDA, Recommended Daily Allowance; RI, Recommended Intake; (a), adjusted by age and sex; 1, mean ± SEM; 2 mean ± SD; 3, median (25th–75th percentile); 4, mean (95% CI); * significant difference with other dietary groups; p < 0.005 ** significant difference with other dietary groups; p < 0.001.