Assessment of the Impact of Salt Iodisation Programmes on Urinary Iodine Concentrations and Goitre Rates: A Systematic Review

Table 1

Main characteristics, results, and conclusions of the studies that used salt iodisation programmes.

Location of studies and references	Study design/period of study	Main results
Isparta- western of Turkey (rual/urban areas)- [27]	“To determine TGR and UIC” in 500 children from six to 11 years old 2001	SC: 68% more in urban areas () compared to in rural areas where it was not refined	MUIC, 70 µg\L: ↑42 µg\L (1997–2001).; - m; il IDD	TGR: 26% (ultrasonography) and 30.4% (palpation): ↑1 and 4.6% (1997–2001) TGR:7.6% in iodised salt consumers and 33% in no consumers. Moderate IDD	Salt iodisation programme without success
Panshan, Zhangwu, and Huanghua- were north, southwest, and coastal region in China (rural areas)- [28]	“To assess the effect of iodine intake, goitre, and thyroid nodules” in adults and children (eight to nine years old) 3338–1999 2708–2004	In Panshan, Huanghua, and Zhangwu: ICS, had a median of <3.4, 25, and 45.6 mg/kg: ↓1.7 and 8.9 mg\kg (Huanghua and Zhangwu) from 1999 to 2004. The iodine content in the water was 10, 7.8, and 201 μg/L	In Panshan, Huanghua, and Zhangwu: MUIC, 87.6, 633.5, and 213.9 µg\L in children. And 96.7, 635.2, and 350.3 µg\L in adults	In Panshan, Huanghua, and Zhangwu: TGP: 20%, 8.3%, and 10% in children.; Moderate IDD in iodine deficiency areas. Mild IDD in iodine excessive areas	Salt iodisation programme without success in iodine deficiency areas but was inequitable in excess areas
Tanzania (rural/urban areas) [10]	“To assess the use of iodised salt, UIC and TGR” In 140758 children and adolescents (six to 18 years old).; 2004	ICS: had a mean do not show but it was 84%.SC, 84%	MUIC 203.6 (192–215) µg\L	TGP: 12.3%: ↓48.4 % (1980–2004).; -Mild IDD	Salt iodisation programme was effective
North of India (rural/urban areas) [26]	“To assess IDD’s control program” in 2860 adults and children (one to 40 years old). 2007	ICS was 6.3 mg/Kg (30%) SC, 25% adequate consumption iodised salt	MUIC 100 (5.0–560) µg/L	TGR: 27.7%: ↓41.3% (1982–2006). TGR, 31% in children with UIC<100 µg\L; -Moderate IDD	Salt iodisation programme was inequitable
Raipur- were Central region in the India (urban/rural areas)- [29]	“Estimate TGR and UIC. ICS. Awareness about IDDs.” in 1177 pregnant women 2006–2007	ICS, was >15 mg\kg of iodine (68%) SC, 66% consumption adequate iodised salt, majority shopkeepers were not aware about iodised salt and legislation regarding it	MUIC, 94 µg\L	TGR: 0.17%	Salt iodisation programme without success
New Zealand (urban/rural areas) [13]	“To assess of mandatory fortification of bread” in 147 children (eight to ten years old) 2010–2011	ICS, >45 mg\kg (90%) SC:28% and associated UIC ()	MUIC, 113.6 (78–159) µg\L: ↑45 µg\L (2002–2011)		Salt iodisation programme was effective
Mexico (urban areas) [23]	“To describe NS in iodine and relate NS “in 1544 children (six to 12 years old); 2010–2011	ICS: was 28.4 ± 9.4 (77.8%) high iodine consumption was the real problem	MUIC, 297 (5–1519) µg\L. Excessive and deficiency iodine coexist		Salt iodisation programme was effective
Zhejiang- eastern in the China (urban/rural areas)- [30]	“To assess the NS in iodine after the 3rd readjustment” in children (from eight to ten years old) 420–2011 1560–2013	ICS was 24 mg/kg: ↓6.4 mg\kg	MUIC, 174.3 (range 586) µg\L: ↓62.8 µg\L from 2011 to 2013.; UIC was more in urban areas compared to rural		Salt iodisation programme was effective
South of Iran (urban areas) [31]	“To assess the NS of iodine two decades after implemented” in such 100 pregnant women, lactating women, and their newborns with three to five days of age.; 2000–2015	ICS: a Median of 26 (21–30) mg/kg and 25 (18–28) in pregnant women and lactating women.; ICS (r = 0.24, ) UIC of newborns was associated with ICS of theirs mother (r = 0.49, )	MUIC, 103 (59–55) μg/L and 77 (42–194) μg/L in pregnant women and lactating women was below compared newborns 198 (84–260) μg/L		Salt iodisation programme without success
Tunisia (rural/urban areas) [22]	“To obtain WHO’s sustainable elimination IDD “in1560 children (six to 12 years old).; 2012	ICS was 22 mg/kg (44.1%) SC, in regions with inadequately iodised salt represented 30% and excessive 66,3%	MUIC, 220 µg\L (199–241 µg\L)		Salt iodisation programme was effective
Sierra Leone (urban/rural areas) [24]	“To assess NS in iodine” in 571 adolescents, 220 nursing, and 154 pregnant women 2013	ICS was >15 mg\kg of salt (81%)	MUIC: - 180.6 µg\L– Pregnant women; - 217.2 µg\L –Teenage girls and; - 196.8 µg\L – Nurses mothers		Salt iodisation programme was effective
32provinces-China (urban/rural areas) [18]	“Analysis achieved challenge IDDs “in 31 million pregnant women and children 2005–2010	SC, >90%	MUIC, 239 µg\L:↓6 µg\L (2005–2010) in children and 184 µg\L in pregnant women	TGR: <5%. Effective elimination IDDs in schoolchildren	Salt iodisation programme was sustaining
Portugal (urban areas) [21]	“To assess NS in iodine and the use of iodised salt” in school-age children (six to 12 years old).; 2015–2016	ICS was 16–54 mg/kg in 2% of people; SC, 16% and was 50% in milk products consumer	MUIC 129 (80–180) µg\L: ↑23 µg\L (2012–2016)		Salt iodisation programme was effective
North-west of Iran (rural/urban areas) [17]	“To assess the TGR and UIC” in 240 children of eight to ten years old.; 2007–2015	ICS: had a mean of 27 mg/kg (97%). SC: 98% of adequately iodised salt	MUIC, 145 μg/L: ↑5 μg/L from 2007 to 2015, ↑6.2% from 2007 in rural compared to 25.7% in urban. UIC>300 μg/L: ↑22.1% from 2007 in urban: And 5.7% in rural. Iodine deficiency is rural and excess in urban areas	TGR: 0.4%: ↓43,6% from 1996	Salt iodisation programme was sustaining
Cassino-Italy (urban areas) [32]	“To assess the NS of/iodine after 10 years programme deployed” in 96 pregnant women cases and 69 nonpregnant in control. 2016–2017	Those who had consumed iodised salt with milk had more UIC (). SC: 42% cover (<90% adequate ICS)	MUIC, 110.6 (15.8–491.3) μg/L was more compared to 97.7 (28.1–1154.3) μg/L in control.; -Insufficient UIC	TGR: Pregnant women had more thyroid volume. -Mild IDD	Salt iodisation programme without success
Kebele village Ethiopia(rural areas) [33]	“To assess the TGR and associated factors” in 356 pregnant women; 2014	ICS: a median of 12.2 (6.9–23.8) μg/L (39.3%) SC: 94% used crystal salt and kept well. Iodised salt cooking addition, light stored, ICS below 15 mg/kg, illiteracy, and age >30, associated with iodine intake	MUIC, 85.7 (45.7–136) μg/L: ↓ 94 μg/L the 1^st (168) to 3rd (74) trimester; - insufficient UIC	TGR: Median of 20 (16–24) %: ↑9% the 1st (13) to 3rd (22) trimester; -moderate IDD	Salt iodisation programme without success
31 provinces- Iran (rual/urban areas) [15]	“To assess NS of iodine” in 18.000 children (eight to ten years old) 2007–2014	ICS: had a mean of 30 mg/kg (63%) SC: 98% used iodised salt and 82% were crystal	MUIC, 161 μg/L in 2013: ↑ 79 μg/L from 2013 (all provinces had UIC > 100 μg/L)	TGR: 5,7%: ↓ 62.3% (1989–2007) in 2013 not have a GTR reporter	Salt iodisation programme was sustaining
31 provinces - China (urban) [16]	“To evaluate the impact of the ICS and NS of iodine “in children (eight to ten years old): 2011 : 14.950 2014 : 48.975 and pregnant women 2011 : 13.932 2014 : 19.500	ICS: had a mean of 25 mg/kg: ↓5.4 mg/kg from the 2011 to 2014 (>90%); SC: > 90% used adequate iodised salt. The policy was based on reduction ICS	MUIC, 197.9 μg/L: ↓40.7 from 2011 to 2014 in children and 154.6 μg/L in pregnant women: ↓29.8 μg/L from 2011 to 2014	TGR: 2.6% in children the same in 2011	Salt iodisation programme was sustaining
Amhara region - Ethiopia (rural areas) [11]	“To assess the TGR and UIC” in infants of six to 11 months old in case (n = 743) and control (n = 654) 2010–2013	ICS: mean does not show.; SC > 90% (in the intervention group). Observed improve UIC level in children the mother that receive iodine salt	MUIC, 228.0 (123.4–411.5) μg/L: ↑102 μg/L from baseline in intervention group more than 155.0 (81.4–283.9)μg/L: ↑140.2 μg/L in control ()	TGR: <5% in both groups	Salt iodisation programme was sustaining
Cameroon (rural areas) [25]	“To monitor the NS of iodine “in children of six to 12 years old. 1990–2018	ICS: had a mean of 72 mg/kg:↑153% (1999–2017). The imported salt contribute to more than 200% of the salt	MUIC, 1145 μg/L: ↑166% from 1999 to 2017. Stem from 2006 to 2018 UIC>300 μg/L: ↑ 756 μg/L. From 2006 the people presented with risk of an adverse effect of health		Salt iodisation programme was inequitable
Shanghai– Central coast in the China (urban areas) Central coast [20]	“To assess NS of iodine, summarized “in children eight to ten years old, the number of years: 1999 : 1320; 2005 : 1223; 2011 : 1234; 2014 : 1510; 2017 : 1215	ICS: had a mean of 24.3 ± 5.6 mg/kg: ↓19,5 mg/kg from 1999 to 2017 SC: >90% (1999–2011) and <90% in 2014–2017 observed reduction of 19,5 mg of iodine/kg in over time	MUIC, 183.0 (114–267) μg/L: ↓53 μg/L in the high iodised salt group, ↑25 μg/L in the low iodised salt group, and ↑16 μg/L in the noniodised salt group from 1999 (X^2 = 35.4: ) to 2017 (X^2 = 10,5: )	TGR: 1.9%: ↓ 1,2% from 1999 to 2017	Salt iodisation programme was sustaining
Tianjin- northeastern in the China (urban areas) - [19]	“To assess the NS of iodine to stopped iodised programme in high water iodine areas” in 399 children aged seven–12 years; 1990–2018	ICS: had a mean do not show areas WIC SC(%) total II(μg/d); < 100 μg/L 56.6 441.1; 100-150 μg/L 21.4 369.4; 150-300 μg/L 11.8 473.9; ≥ 300 μg/L 5.1 576.8. The salt iodisation programme stopped in areas with iodine water ≥300 μg/L, in areas with iodine in water <100 μg/L had also higher consumption of iodine but eliminated sustaining IDD	Areas WIC UIC (μg/L) < 100 μg/L 217.2 (157.93–290.58 100–150 μg/L 187.65 (133.20–237.05) 150–300 μg/L 209.15 (137.23–258.38) ≥ 300 μg/L 476.30 (332.20–639.30)	TGR: in areas with UIC ≥ 300 μg/L was 10% and 27% thyroid nodules (). In areas with WIC ≥300, 150–300, 100–150, and < 100 μg/L were 11%, 12%, 38%, and 97% respectively. Observed mild IDD in people had risk of adverse effect of health	Salt iodisation programme was without success in areas with iodine concentration in water ≥300 μg/L but in areas with <100 μg/L it was sustaining
Antalya- southern in Turkey (urban) [14]	“To assess the NS of iodine “in 1.594 children of six to 14 years old.; 1999–2015	SC: >90%.	MUIC, 163.3 (105.3–254.8) μg/L: ↑ 101 μg/L from 1999 to 2015 ().; In 2015 not registered iodine deficiency	TGR: 0,3%: ↓33,7% from 1999 to 2015 ()	Salt iodisation programme was sustaining

ID: iodine deficiency; IDD: iodine deficiency disorders; NS: nutrition status. ↓: low; ↑: raised; <: less; >: higher; ±: standard deviation; ICS: iodine concentration in salt; MUIC: median Urinary iodine concentration; UIC: urinary iodine concentration; WIC: water iodine concentration; TGP: total goitre rate; SC: salt coverage or consumption, II: iodine intake.