The author has critically reviewed the editorial and raised important issues which require clarifications. The issue of continued prevalence of goiter inspite of availability of iodised salt may be due to the fact that it takes few years for goiter to disappear in school age children after the urinary iodine excretion levels are corrected. The production of iodised salt in India was only 7 lakh tonnes in 1986 and it has increased to nearly 45 lakh tonnes in 1997. The recent increase "in production and consumption of iodised salt during last five years was possibly responsible for adequate iodine nutriture in population but continued high prevalence of goiter in the five districts included in the studies. Since in India, out of 275 districts surveyed, 235 (>80%) were endemic for iodine deficiency, the Government of India rightly adopted the policy of universal salt iodisation. A targeted supply of iodised salt to endemic districts in this scenario is op- erationally neither feasible nor cost effective. It has been documented earlier also that with interruption in supply of iodised salt, goiter reappeared in the population.

Dr. Shah's observation that "majority of iodised salt sold in the market is not iodised at all" probably relates to mass media. However, the editorial pertains to research studies on iodine content of salt and iodine status in population collected by utilizing scientifically valid sampling methodology.

Reserch on losses of iodine from salt have clearly documented that only small quantities of iodine are lost from the iodised salt packed in LOPE pouches which are air tight and moisture proof. However, the losses of iodine are much more from the salt when packed in gunny bags or HOPE bags when kept in open ground exposed directly to rains and sun light.

The suggestion to undertake a study on losses of iodine at different stages of production to point of consumption is welcome. I agree with the comments for not using iodised oil in prevention of IDO.

The consumption of iodised salt in the quantity available to the consumers (15 parts per million of iodine) is absolutely safe; the excess of iodine consumed is not retained by the body and is excreted through urine. The average daily intake of iodine in Japan has been reported to be 3000 micrograms which is 20 times more than the recommended dietary allowance value in India. Studies carried on 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 ate not different from those in non-endemic areas of other countries indicating their adaptation to excess iodine intake. Existence of this type of adaptation is also confirmed by animal experiments. Further- more, there is no evidence that the incidence of thyroid disease in Japan is higher than those in non-endemic areas of other countries. Thus even if those who do not stay in known iodine deficient areas or who do not have any visible manifestation of iodine deficiency consume iodine fortified salt, it is totally safe for them( 1-7).

Allergic reactions of iodine are quite rare and incidence figures for such reactions are virtually not available. It has been reported that iodine prophylaxis for endemic goitre caused a transient increase of 0.01-0.04% cases over the basal incidence of hypothyroidism peaking at 1-3 years and normalising in 3-10 years despite continued iodine exposure. It has been found in USA and Brazil that inspite of extensive exposure to iodine, iodine hyperthyroidism seems to be a rare complication(3,6-8).
 

Umesh Kapil,
Additional Professor,
Department of Human Nutrition,
All India Institute of Medical Sciences,
New Delhi I/O 029, India.