Umesh Kapil
Priyali Pathak
From the Department Human Nutrition, All
India Institute of Medical Sciences, New Delhi 110029, India.
Reprint requests: Dr. Umesh Kapil, Additional
Professor, Department of Human Nutrition, All India Institute of
Medical Sciences, New Delhi 110 029, India
E-mail:
[email protected]
In India, the disorders resulting from iodine
deficiency are present throughout the country. Out of 275
districts surveyed by various Government of India institutions and
Central Goiter Survey Teams in 25 States and 4 Union Territories,
235 have been found to be endemic for Iodine Deficiency Disorders
(IDD). In view of magnitude of the problem as well as considering
the technical, administrative, financial and operational
feasibility, the Government of India took a decision in 1984 to
iodize all edible salt in the country, i.e.,
Universal Salt Iodization (USI). However, recently concerns have
been expressed by some quarters in mass and electronic media about
the use of iodized salt and the policy of Universal Salt
Iodization in the country. A National Consultation was convened on
21st April 1999 to discuss the cumulative scientific and
epidemiological evidence on "Benefits and Safety of Iodized
Salt" in the prevention and control of IDD. The objective of
the Consultation was to develop a National Consensus Document on
Benefits and Safety of Iodized Salt based on hard scientific data.
The participants of the National Consultation
included scientists of various Departments of the Government of
India namely Indian Council of Medical Research, Indian Council of
Agricultural Research, Ministry of Health and Family Welfare,
Ministry of Human Resources Development, Department of Women and
Child Development, National Institute of Health and Family
Welfare, All India Institute of Hygiene and Public Health,
Planning Commission and National Institute of Public Cooperation
and Child Development. Representatives of professional
organizations like Nutrition Foundation of India, the Nutrition
Society of India, Indian Academy of Pediatrics, Indian Association
of Preventive and Social Medicine, Indian Public Health
Association, Thyroid Association of India, Endocrinology Society
of India, Association of Physicians of India, etc. also
participated. Program managers from Salt Department, International
and Bilateral Agencies like United Nations Children’s Fund
(UNICEF), United States Agency for International Development (USAID),
World Bank, World Health Organization (WHO), Micronutrient
Initiative and Cooperative for American Relief Everywhere (CARE)
also participated.
The following recommendations were made in the
National Consultation.
1. Based on scientific studies of iodine
balance over a 24 hour period, a safe daily intake of iodine has
been estimated to be between a minimum of 50 mcg and a maximum
of 1000 mcg. A generally accepted desirable dietary iodine
intake by an adult is 100-300 mcg/day.
2. Iodine has relatively wide margin of
safety. Acute and chronic toxicity studies with sodium iodate
have been carried out. Results of these long-term animal and
human experiments in doses comparable to those that are used in
prophylaxis, have failed to produce toxic signs. On the basis of
toxicological studies it has been confirmed that potassium
iodate is very safe at the level used in salt iodization. This
has been also confirmed on the basis of worldwide experience of
salt iodization programs.
3. The average daily intake of iodine in
Japan has been reported to be 3000 micrograms, which is 20 times
more than the RDA value of 150 mcg in India. Studies carried out
in normal Japanese population have shown that they are
biochemically and clinically eumetabolic inspite of the
consumption of large amounts of iodine. The values for their
thyroid hormone are not different from those in non-endemic
areas of other countries indicating their adaptation to excess
iodine intake. Existence of this type of adaptation has also
been confirmed by animal experiments. There is little
indica-tion that iodine in the amounts noted influences the
prevalence of any of the thyroid diseases.
4. The average daily salt intake in India is
10 g. Consumption levels are within the 5-15 g/day range
for children and adults. As per Government of India
recommendations, the level of salt iodization (quantity of
iodine added to salt) should provide a minimum of 150 mcg of
iodine per day at the consumption level. From the average daily
intake of 10 g iodine fortified salt, the estimated availability
of iodine would be 150 mcg, of which about 30% is lost during
cooking. The remaining 105 mcg is ingested and from this about
70% is absorbed by the body. This means approxi-mately only 73.5
mcg is absorbed per day from iodine fortified salt. This
quantity when added to the iodine daily consumed through food
will be broadly comparable to the daily physiological need of
the body. Indeed urinary iodine excretion studies in the post
iodization phase show that all over the India, the salt
iodization is not more than 300 mcg per day. Thus, the level of
salt iodization is totally safe in our country.
5. Since iodine, when ingested in large
amounts, is easily excreted in the urine, iodine intake even at
very high levels (milligram amounts) can be safe. It is
documented scientifically that through adaptive mechanisms,
normal people exposed to excess iodine remain euthyroid and free
of goiter. It is not correct to attribute skin reactions such as
rashes and acne to iodized salt. Physiological levels of iodine
intake do not cause "Iodism". For example, among
20,000 children in the USA suffering from allergy during the
period 1935-1974, not a single case was reported of allergic
hypersensitivity to iodine in food. Following publication in
Annals of Allergy of a request for notification of allergy to
iodine, not a single report was recorded between 1974 and 1980.
However, high intakes of dietary iodine may induce
hypothyroidism in autoimmune thyroid diseases and may inhibit
the effects of thionamide drugs. Iodine-induced hyperthyroidism
is an adverse effect, which may occur primarily in older people
where severely iodine deficient populations increase their
iodine intake, even when the total amount is within the usually
accepted range of 100-200 mcg/day. Epidemiologically
iodine-induced hyperthyroidism represents a transient increase
in the incidence of hyper-thyroidism, which disappears, in due
course with the correction of iodine deficiency. From a public
health point of view, the benefits of correcting iodine
deficiency through universal salt iodization greatly outweigh
the risk of iodine-induced hyperthyroidism.
6. The daily iodine intake of upto 1 mg (1000 mcg) appears to
be entirely safe. Iodization of salt at a level that assures an
intake of 150-300 mcg/day keeps iodine intakes well within daily
physiological needs for all populations, irrespective of their
iodine status. In India, daily consumption of 10 g of salt
containing 15 parts per million of iodine would add a maximum of
only 150 mcg of iodine. Thus, the likelihood of exceeding an
iodine intake of 1 mg/day from iodized salt is negligible.
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