Iodine Deficiency, in China
Abstract
Iodized salt is the best means of providing iodine
to deficient populations, and it has been used successfully and
safely for 70 years around the world. In China about 450 million
people live in iodine-deficient areas. The prevalence of endemic
goitre in 7- to 14-year-old children was estimated to be 20% (7
million cases). The Chinese government has undertaken to
eliminate iodine-deficiency disorders by the year 2000, and the
manufacture and use of iodized salt throughout China has been
compulsory since early 1995. Currently, potassium iodate is
used. National regulations require the iodine content of iodized
salt to be no less than 30 mg/kg in the salt-processing plant,
no less than 25 mg/kg in the market, and no less than 20 mg/kg
in the household. According to sporadic sample checking,
however, the iodine content of salt in the market and the
household is far from satisfactory. The loss of iodine during
cooking is as high as 50% to 70%. The major problems in the
fortification of salt with iodine in China are the use of
uniodized salt in remote areas, an unsatisfactory system for
monitoring the quality of iodized salt, the lack of knowledge
and skill among marketing staffs, the loss of iodine during
storage and cooking, and the lack of nationwide systematic
studies to monitor the effectiveness of iodized salt in the
control of endemic goitre.
Introduction
About 1,500 million people, or nearly
one-third of the earth’s population, live in areas of iodine
deficiency. Its consequences, the iodine-deficiency disorders,
include irreversible mental retardation, goitre, reproductive
failure, increased child mortality, and socio-economic
compromise. All of these results can be prevented by sufficient
iodine in the diet. Eliminating iodine deficiency is recognized
as one of the most achievable of the goals that the 1990 World
Summit for Children set for the year 2000.
Iodized salt
is the best means to provide iodine to iodine-deficient
populations. It is physiological, simple, practical, and
effective. It has been used successfully and safely for over 70
years in programmes around the world. The Codex Alimentarius
standard for food-grade salt permits the use of sodium and
potassium salts of iodides and iodates in the iodization of
salt. The level of fortification that has been used ranges from
30 to 200 ppm, which will provide enough iodine to meet the
requirement of 150 to 200 mg per
person per day [1]. In China, although iodized salt has been
commercially available for more than 40 years, it was 1995
before its use became mandatory throughout the country.
Prevalence of iodine deficiency and iodine-deficiency disorders
in China
About 450 million people live in
iodine-deficient areas of China, and more than 30% of the total
population is at risk for iodine-deficiency disorders. The
average prevalence of endemic goitre in children between the
ages of 7 and 14 was estimated to be 20% in 1995. All of
mainland China’s 30 provinces have reported the occurrence of
iodine-deficiency disorders, primarily endemic goitre; however,
there are significant differences in prevalence among geographic
regions. There is at least a 40-fold difference between the
county with the lowest prevalence and the county with the
highest prevalence. It is estimated that in China in 1993 and
1994, there were more than 7 million cases of endemic goitre and
more than 200,000 cases of cretinism [2].
It is widely
acknowledged that most iodine-deficient areas are located in
hilly or mountainous regions. However, it has been uncertain
whether iodine deficiency is an issue of public health concern
in large cities in China. A recent investigation demonstrated
that subclinical iodine deficiency (urinary iodine < 100
mg/L) was quite common in schoolchildren in some large
cities, such as Shanghai, Zhengzhou, Hefei, and Fuzhou (table 1)
[3].
Government actions to control
iodine-deficiency disorders
The Chinese government has
undertaken to eliminate iodine-deficiency disorders by the year
2000. In 1994 the Ministry of Health and the Ministry of Light
Industry jointly promulgated the programme outlines for
accomplishing this. The strategic goals of this project are the
following: all salt for human and animal use should be iodized;
95% of the population should use iodized salt; more than 95% of
special populations (newly married women, pregnant women,
lactating mothers, infants, and young children) should use
iodine oil; and 95% of the counties should meet the criteria for
elimination of iodine-deficiency disorders (prevalence of
endemic goitre in schoolchildren < 5%).
To ensure the
mandatory nationwide use of iodized salt, in August 1994 the
State Council of the People’s Republic of China promulgated the
Regulation on Adding Iodine to Salt to Eliminate Health Hazards
Due to Iodine Deficiency. It stipulated that the health
administration department in the State Council shall be
responsible for the control of health hazards caused by iodine
deficiency and the health inspection and supervision of iodized
salt, and that the salt administrative department in the State
Council shall be responsible for the manufacture and marketing
of iodized salt. According to the regulation, the mandatory
manufacture, distribution, and use of iodized salt throughout
China began on 1 October 1994 (Order No. 163 from the State
Council of the People’s Republic of China, 23 August 1994).
Effectiveness of use of iodized salt
Although
the nationwide use of iodized salt was not started until early
1995, the effectiveness of iodized salt in the control of
endemic goitre was clearly shown in several observations and
trials. Table 2 shows the consistent reduction in the prevalence
of goitre at the provincial, city, and county levels, where the
use of iodized salt was mandatory in every household, although
no parallel control population was available in those
observations [4-11]. However, considering the large differences
in climate, dietary patterns, cooking habits, and other
lifestyle factors among various parts of China, the
effectiveness of iodized salt in controlling iodine-deficiency
disorders needs further studies and long-term monitoring.
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