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Table 2 Descriptive of estimated iodine intake from the I-FFQ and food diary (μg/day), and urinary iodine concentration (UIC, μg/L) and estimated iodine intake from UIC (μg/day) in pregnant women (gestational week 18-19) enrolled in the Mommy’s Food study

From: Validation and reproducibility of a new iodine specific food frequency questionnaire for assessing iodine intake in Norwegian pregnant women

  N Mean (SD) f Median (p25-p75) p5-p95
Estimated iodine intake, I-FFQ, μg/day a
 Diet 124 134 (73) 123 (89–157) 51, 309
 Diet and supplements 124 202 (108) 202 (106–275) 60, 377
Estimated iodine intake, food diary, μg/day b
 Diet 134 116 (51) 105 (80–153) 42, 203
 Diet and supplements 134 171 (99) 151 (87–262) 47, 342
Urinary iodine concentration (UIC), μg/L c
 All participants 134 103 (56) 94 (62–130) 36, 210
 Non-supplement users d 87 89 (49) 77 (58–120) 31, 172
 Supplements users d 47 129 (58) 130 (77–160) 49–270
Estimated iodine intake from UIC, μg/day e
 All participants 117 166 (93) 147 (104–206) 61, 404
 Non-supplement users d 75 135 (69) 119 (83–169) 46, 273
 Supplement users d 42 220 (105) 202 (143–262) 73, 439
  1. a Iodine specific food frequency questionnaire (I-FFQ)
  2. b Iodine specific food diary from six consecutive days
  3. c Pooled sample of spot urinary samples from six consecutive days
  4. d Reported use of iodine containing supplement in the food diary
  5. e Estimated from the equation: Urinary iodine concentration (μg/L) × 0.0235 × body weight (kg) (IOM 2001) [28]. Self-reported current body weight used for estimation (data of n = 17 missing)
  6. f Differences between the different methods were tested by Wilcoxon’s signed-rank test. Difference between estimated iodine intake from I-FFQ and food diary (without supplements): P = 0.030; estimated iodine intake from I-FFQ and food diary (with supplements): P = 0.002; estimated iodine intake from UIC and food diary: P = 0.882; estimated iodine intake from UIC and I-FFQ: P = 0.001