Iodine as a health hazard

Sir,—In his recent article on Medical Research in New Zealand, Dr. Adams has been all too modest about the output of work from Dunedin, and especially about his own major contribution to the disease, thyrotoxicosis. His failure to detect any medical research elsewhere in New Zealand is hardly surprising. Until recently, research has been discouraged in the other main centres, and even today a flair for medical investigations is likely to hinder a doctor seeking to advance in a competitive specialty. It is difficult for the lay person to understand medical conservatism, which is there to protect patients from hasty and possibly dangerous alterations of accepted medical practice.

Two examples of haste were the use of thalidomide, and the great SV40 virus experiment, the latter involving, as it does, so many of today's youth up and down the world. It is as a medical conservative, that I wish to take up one point in his article.

Dr. Adams writes that legislation is needed to prevent the sale of non-iodised salt, where marketed at a price lower than iodised salt, or at least I hope that is what he means. In the present era of quickfire legislation, we could easily find ourselves with a law prohibiting the sale of non-iodised salt. There should be no doubt in our minds as to the health hazard of endemic goitre, an unpleasant and disfiguring deficiency disease.

The introduction of iodised salt in the 1920s in the proportion of one in 200,000 was a wise and necessary measure, and in due course, as in Switzerland, this amount of iodination may have eliminated goitre. In 1939, it was considered that the programme should be hurried up, and the proportion was increased to one in 20,000. Is it possible that at this point we took a leap into the dark?

From the experience of Switzerland, it should be possible to eliminate goitre with one in 100,000 to one in 200,000 proportions of iodination. The World Health Organisation recommends a level of one in 100,000. For about 25 years we have been using about four or five times this amount. The proportion of one in 100,000 seems slightly more than adequate to correct an existing iodine deficiency. Any extra iodine is unnecessary, and at some point begins to act as a suppressor to the pituitary thyroid axis.

Does the extra iodine do any harm? To this question, there does not seem to be any definite answer, and I believe that the question has not even been seriously considered. Certainly the iodised salt programme should come into any consideration of postwar health in New Zealand, together with the many other factors which have been introduced into our environment. It would be incorrect to consider that our health has improved since the war years, and in some respects, particularly after middle age, there has been a significant deterioration. Let us view the subject of goitre prevention, with our eyes not only on the thyroid, but also on the whole of the human physiology. We have in New Zealand, comprehensive medical statistics for the postwar years and a homogenous racial background which makes us an ideal group for epidemiological studies, on a vast scale.

Dr. J. Logan.

Wellington Hospital.