Iodine

Iodine functions as an essential component of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). Thyroid hormones are involved in the regulation of various enzymes and metabolic processes.

Iodine deficiency can lead to goitre, hypothyroidism and developmental abnormalities. Excessive iodine intakes have been associated with thyroiditis, goitre, hypothyroidism, hyperthyroidism, sensitivity reactions, thyroid papillary cancer and acute responses (e.g., nausea, vomiting, diarrhea) in some individuals.

Dietary Sources

Dietary sources of iodine include iodized salt, dairy products and seafood. The iodine content of plants depends on the iodine content of the soil in which it grows. Due to the widespread presence of iodine-deficient soils in Canada, the addition of iodine to salt for table or household use was made mandatory in 1949.

Assessment of Iodine Status

The iodine status of Canadians was assessed by measuring urinary iodine levels through a casual sample (single occasion) from each respondent. Since most ingested iodine is excreted in the urine (over 90%), urinary iodine is a good marker of very recent dietary iodine intake. Urinary iodine concentration is influenced by both iodine intake and fluid consumption. At the individual level, this can vary from day to day, however, at the population level, this variation tends to even out. In a large population survey like the CHMS, this measure provides an adequate assessment of the population's iodine status. Urinary iodine can also be expressed in relation to another compound in urine, creatinine, which adjusts for fluid intake. Both urinary iodine and iodine-to-creatinine ratio are presented in the tables below.

Table 1: Urinary Iodine (μmol/L)
Mean and selected percentiles of urine concentrations, by DRI age groups and sex, Canada household population, Canadian Health Measures Survey 2007 to 2009

E Data with a coefficient of variation (CV) from 16.6% to 33.3%; use with caution

F Data with a coefficient of variation (CV) greater than 33.3%; suppressed due to extreme sampling variability.

Sex
Age Group
n
Mean
(95% conf.
interval)
Selected percentiles
 (95% confidence intervals)
5th
10th
25th
50th
75th
90th
95th
Males 9-13 444 1.87
(1.47,2.27)
0.32E
(0.18,0.47)
0.46
(0.35,0.58)
0.82
(0.65,0.99)
1.41
(1.12,1.69)
2.06
(1.61,2.51)
3.66E
(2.15,5.17)
5.61
(4.13,7.09)
14-18 295 1.73
(1.40,2.06)
0.38E
(0.21,0.54)
0.53
(0.36,0.70)
0.78
(0.63,0.94)
1.30
(1.00,1.60)
2.10
(1.64,2.57)
3.35
(2.76,3.93)
4.47
(3.59,5.34)
19-30 293 1.62
(1.12,2.11)
0.18E
(0.08,0.27)
0.27
(0.18,0.36)
0.64E
(0.40,0.87)
1.01
(0.81,1.22)
1.64
(1.29,1.98)
2.89E
(1.16,4.61)
5.29E
(2.06,8.53)
31-50 658 1.46
(1.18,1.74)
0.18E
(0.09,0.28)
0.31
(0.22,0.39)
0.60
(0.52,0.67)
0.99
(0.88,1.09)
1.52
(1.36,1.69)
2.40
(1.55,3.25)
4.26E
(2.33,6.20)
51-70 553 1.58
(1.32,1.84)
0.32
(0.23,0.41)
0.42
(0.30,0.55)
0.75
(0.64,0.87)
1.17
(1.04,1.29)
1.77
(1.59,1.94)
2.93
(2.22,3.64)
4.12
(3.03,5.22)
71-79 175 1.82
(1.45,2.19)
0.26E
(0.08,0.43)
0.46E
(0.21,0.70)
0.77
(0.62,0.92)
1.20
(1.07,1.34)
1.61
(1.34,1.88)
2.62E
(1.46,3.79)
4.36E
(2.43,6.29)
19-79 1679 1.55
(1.27,1.83)
0.21
(0.14,0.28)
0.33
(0.26,0.40)
0.65
(0.59,0.72)
1.05
(0.96,1.14)
1.66
(1.46,1.85)
2.73
(1.89,3.57)
4.48
(2.93,6.03)
Females 9-13 403 1.64
(1.40,1.87)
0.24
(0.16,0.32)
0.33E
(0.17,0.49)
0.77
(0.54,1.00)
1.33
(1.06,1.61)
2.04
(1.73,2.35)
3.27
(2.41,4.12)
4.46
(3.26,5.65)
14-18 295 1.75
(1.32,2.19)
0.23
(0.15,0.32)
0.32E
(0.19,0.46)
0.65E
(0.26,1.05)
1.22
(1.02,1.42)
1.93
(1.45,2.41)
3.99E
(2.39,5.60)
5.55
(3.68,7.41)
19-30 331 1.28
(0.91,1.64)
0.19E
(0.09,0.28)
0.27
(0.18,0.36)
0.57
(0.42,0.73)
0.95
(0.83,1.08)
1.35
(1.00,1.69)
2.29E
(1.03,3.55)
3.96E
(1.59,6.33)
31-50 792 1.20
(0.99,1.42)
0.17
(0.12,0.22)
0.25
(0.19,0.31)
0.43
(0.33,0.52)
0.82
(0.66,0.99)
1.42
(1.23,1.60)
2.27
(1.71,2.83)
3.23
(2.24,4.21)
51-70 579 1.36
(1.12,1.61)
0.20E
(0.11,0.28)
0.30
(0.25,0.35)
0.53
(0.44,0.62)
0.92
(0.84,1.00)
1.46
(1.27,1.66)
2.41
(1.80,3.01)
3.47
(2.67,4.28)
71-79 178 1.59
(1.07,2.12)
F
F
0.61E
(0.33,0.90)
1.23
(0.92,1.54)
1.80
(1.38,2.22)
3.22E
(1.89,4.55)
4.05E
(2.35,5.74)
19-79 1880 1.29
(1.08,1.51)
0.18
(0.12,0.24)
0.28
(0.24,0.33)
0.50
(0.41,0.59)
0.92
(0.82,1.03)
1.45
(1.26,1.63)
2.37
(1.83,2.91)
3.46
(2.51,4.40)

Notes:

Total household population aged 9 to 79, except those meeting the exclusion criteria.  For more information regarding the exclusion criteria, please refer to the  Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 1.

Bootstrap weights included with the dataset were used to estimate the 95% confidence intervals for all means and percentiles assuming a student’s t-distribution with 11 degrees of freedom.

Urinary iodine was assayed chemically by the Sandell-Kolthoff reaction.

Measurements that fell below the limit of detection (LOD) were assigned a value equal to half the LOD.  The limit of detection is 0.158 μmol/L

Data source: Canadian Health Measures Survey, Cycle 1.

Table 2: Creatinine corrected urinary iodine (mmol iodine/mmol creatinine)
Mean and selected percentiles of urine concentrations, by DRI age groups and sex, Canada household population, Canadian Health Measures Survey 2007 to 2009

E Data with a coefficient of variation (CV) from 16.6% to 33.3%; use with caution

F Data with a coefficient of variation (CV) greater than 33.3%; suppressed due to extreme sampling variability.

Sex
Age Group
n
Mean
(95% conf.
interval)
Selected percentiles
 (95% confidence intervals)
5th
10th
25th
50th
75th
90th
95th
Males 9-13 436 255
(208,303)
66
(55,78)
83
(69,97)
113
(99,127)
175
(146,203)
286
(231,342)
457
(297,617)
747E
(362,1131)
14-18 293 155
(128,182)
41
(36,46)
49
(40,58)
70
(59,80)
114
(83,144)
196
(157,236)
274
(224,325)
373
(272,474)
19-30 283 143
(104,183)
34
(29,39)
40
(29,50)
60
(46,74)
91
(66,115)
155
(138,171)
231
(163,298)
F
31-50 634 152
(134,170)
36
(33,39)
45
(39,51)
64
(55,73)
99
(88,109)
169
(145,193)
317
(249,386)
460
(311,608)
51-70 544 177
(137,216)
49
(36,63)
55
(49,61)
79
(69,89)
123
(103,142)
196
(169,223)
333E
(200,465)
490
(324,657)
71-79 174 259
(176,342)
56
(47,65)
67
(54,79)
83
(69,97)
129
(99,159)
215
(168,262)
349
(222,476)
761E
(315,1206)
19-79 1635 164
(142,186)
36
(32,40)
48
(42,54)
69
(62,76)
107
(97,116)
176
(156,197)
304
(231,376)
461
(323,600)
Females 9-13 393 216
(187,245)
58
(38,78)
70
(54,87)
102
(85,119)
170
(152,188)
255
(209,300)
369
(270,468)
556
(404,709)
14-18 288 160
(131,188)
43
(39,48)
53
(41,65)
78
(67,89)
113
(95,131)
179
(151,206)
334E
(212,456)
428
(310,546)
19-30 314 163
(137,189)
44
(41,47)
50
(43,57)
72
(61,83)
116
(99,134)
190
(157,222)
347
(253,441)
494
(354,634)
31-50 761 198
(170,227)
55
(43,66)
69
(60,78)
94
(82,105)
140
(122,159)
220
(189,252)
393
(282,503)
540
(442,638)
51-70 566 238
(203,273)
58
(46,69)
77
(61,93)
117
(100,134)
174
(144,205)
278
(236,320)
426
(296,557)
598
(470,726)
71-79 176 353
(276,430)
83E
(50,117)
102
(76,128)
146
(113,179)
238
(153,322)
434
(339,528)
593
(406,780)
767
(715,819)
19-79 1817 213
(193,233)
51
(46,57)
65
(58,71)
96
(88,103)
149
(137,161)
247
(221,272)
431
(362,500)
569
(505,633)

Notes:

Total household population aged 9 to 79, except those meeting the exclusion criteria.  For more information regarding the exclusion criteria, please refer to the  Canadian Health Measures Survey (CHMS) Data User Guide: Cycle 1.

Bootstrap weights included with the dataset were used to estimate the 95% confidence intervals for all means and percentiles assuming a student's t-distribution with 11 degrees of freedom.

Data source: Canadian Health Measures Survey, Cycle 1.

Related Resources

Chapter on  Iodine in Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001)

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