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Iodine deficiency

Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inland areas where no marine foods are eaten—iodine deficiency gives rise to goitre, so called endemic goitre. more...

ICF syndrome
Ichthyosis vulgaris
Imperforate anus
Inborn error of metabolism
Incontinentia pigmenti
Infant respiratory...
Infantile spinal muscular...
Infective endocarditis
Inflammatory breast cancer
Inguinal hernia
Interstitial cystitis
Iodine deficiency
Irritable bowel syndrome

Iodine deficiency is particularly common in the Western Pacific, South-East Asia and Africa. Iodine deficiency is also associated with poverty. In many (but not all) such areas, this is now prevented by the addition of small amounts of iodine to table salt in form of sodium iodide, potassium iodide, potassium iodate—this product is known as iodized salt.

Iodine deficiency is the leading cause of mental retardation, producing typical reductions in IQ of 10 to 15 IQ points. It has been speculated that deficiency of iodine and other micronutrients may be a possible factor in observed differences in IQ between ethnic groups: see race and intelligence for a further discussion of this controversial issue.

In a not widely accepted theory, geographer Jeremy Dobson has suggested that Neandertals exhibit characteristics similar to modern humans with iodine deficiency, or cretinism.


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Please pass the iodine! - iodine deficiency - part one of three
From Saturday Evening Post, 3/1/97 by Woods Hutchinson

Editor's Note: The linking of iodine deficiency to goiter, cretinism, and endemic low IQ was one of the great American medical discoveries of the 20th century. The dramatic story was chronicled in 1925 in a classic Hutchinson's Evening Post article by Woods Hutchinson, M.D. More than 70 years later, Hutchinson's musings about salt, iodine, and mankind remain fascinating reading, especially because iodine deficiency still plagues millions around the world. Lack of iodine is the largest preventable cause of mental retardation worldwide.

Part I of III

It has always been one of the puzzles--one might almost say mysteries--of physiology why salt plays and has always played such an extraordinary part in our diet, and why all men everywhere, in all times, have craved it so eagerly and insisted upon having its pungent taste in their food at no matter what cost. It is not a food, in the sense of giving off energy or heat to the body, because it has none itself and is not broken down in the body, but passes through the whole system and out again unchanged as it entered. Yet cut off the supply and we become as restless and uncomfortable and generally miserable and inefficient as though we had been deprived of bread or meat or potatoes. Now we are beginning to suspect that half our mysterious craving for its savor and salty tang is due to the brown witch Iodine, who rides inland with it on the spray of the same stormwind.

The salt tax has always been one of the cruelest and one of the most valuable and easily collected of all the taxes and monopolies of both classic and medieval times, because people simply would not go without salt.

Nor is the craving in any sense a morbid or imaginary one, although it has frequently been denounced as both. One of the most vivid and interesting instances of its intensity and genuineness was furnished by a brigade of Stonewall Jackson's famous light infantry, during the Civil War, whose astoundingly rapid and prolonged marches had given them the name of "Jackson's Foot Cavalry." This was no mere figure of speech, for they actually beat and tired out crack cavalry corps in one or two of their extraordinary races. Like the troops of Garibaldi and other born commanders, Stonewall's men traveled absolutely unencumbered by baggage, with nothing but their rifles and ammunition, and in cold weather a blanket, and what food they could carry in their haversacks. In one remarkable march across the mountains and down into the Shenandoah Valley, his racing infantry ran completely out of food, and for the last three days subsisted entirely upon green corn, which they picked in the fields and roasted in their camp fires. When they burst like a thundercloud upon the astonished and unsuspecting enemy, who thought them a hundred miles off, and sent him flying up the valley, leaving all his supplies behind him, the first thing that they rushed for among the supplies was neither meat nor bread nor sugar, but salt. They flung themselves upon the barrels, split them wide open and snatched up the priceless condiment by handfuls, crunching it down as if it were the finest of bonbons or candy. As an observer remarked, they were just as crazy for salt as colts in a clover pasture.

Wrong Guesses at the Truth

As soon as modern science arrived and began to make a systematic study of the diet, figuring out a rational basis for our likings for different kinds of foods and flavors, it began to speculate upon the why and wherefore of salt on the menu. Not only do we insist upon its taste in most of our foods, but it is the only regular food condiment which we will not trust to the discretion of the cook, but insist upon having on the table in order that we may adjust its proportions to each of our own individual likings.

The first and most natural supposition was that our food did not contain enough of it to maintain our bodies in health and make good the daily drain from the body by the kidneys. But forty years ago Bunge showed by a series of careful and painstaking tests that the materials of an average diet, in their raw or uncooked state, contained quite sufficient salt to supply the daily need of the body. And a further puzzle lay in the well-known fact that carnivorous animals living almost entirely upon flesh had very little craving for salt, because the blood and muscles of their victims contained a sufficient supply, while herbivorous animals, such as deer, cattle, buffalo and the like, had a strong craving for salt and would travel long distances to salt licks or salt springs in order to obtain it. But an analysis of the grass, hay and grains which made up the food of the grazing animals showed that these, too, contained salt in almost adequate amounts for the requirements of the body. So that he had to devise a labored and rather clumsy explanation as to its being needed to neutralize the large amounts of potash salts which were present in leaves and grains.

In other words, our salt craving, as well as that of the animals, was apparently as absolute a mystery as it had been in the beginning.

Of the reality of it no one in the early days could be in the slightest doubt, for one of the gravest fears that the hardy pioneers after and under Daniel Boone felt about crossing the mountains and going over into the fertile paradise of game and fish beyond was that they would be going too far away from their salt supply on the coast. So the finding of the famous salt licks and springs of Kentucky, Indiana and Southern Michigan was one of the greatest factors in making quick and sate the settlement of the Mississippi Valley.

What Michigan Owes to Salt

The unkind use made of these salt licks and salt springs by the pioneer hunters lying in wait to shoot down the deer which came to drink the water or lick the exposed salty rocks, was only a very small and romantic fragment of their value and importance to the white settlers. They, too, felt the cosmic urge of the salt craving and flocked to the springs for their supply of salt as eagerly as the deer had for millions of years before them.

As the pioneer settlements spread west and northwest like mushrooms, and the population of the Middle West and Great Lakes areas became denser, these mild surface leakages of salt became inadequate to meet the demand and attempts were made to increase it by boring deep wells into the lower strata. Then curious things began to happen.

One such boring in a lakeside state scored a partial success by tapping an abundant flow of water fairly stiff with salt; but when it came to be collected for purposes of filtration it was found to be so nauseous and bitter, so full of brownish coloring matter, as to be almost incapable of purification for human use with the rough methods of that time. So the well was reluctantly abandoned and turned over to the farmers near whose farms it was bored, to be used for watering their cattle and sheep.

Now it so happened that in that district farmers had been unable to grow their necessary supply of wool by reason of the fact that sheep simply would not thrive. Grown sheep brought in from other districts did fairly well, but just as soon as lambs began to be born, instead of sturdy, active youngsters, the majority of them came into the world feeble, deformed and imperfectly developed, affected often by a curious type of apparent paralysis which rendered them unable to walk.

Such had been the experience of the farmers in the neighborhood of this salt well. But to their surprise and delight, as soon as their sheep were given access to the bitter brown water of this deep salt well they began to pick up at once. The next crop of lambs was fully formed, vigorous, and healthy and the region became perfectly fit for the breeding and production of sheep.

A short time later improved methods for the purification of brines and the production of a whiter and more attractive table salt were invented, and another company took courage to attack this bitter well by the new methods. To their great gratification they succeeded in filtering off the dark color and nauseous-tasting element in the water and leaching out a good supply of pure, white, crystallized salt, which was put upon the market and had an excellent sale. They had a dark-brownish residue of bitter taste; and with a praiseworthy desire to utilize their product, they left enough of the coarser and less pure salt to crystallize and form a reddish-brown product known as rock salt or cattle salt, and put that on the market for the use of sheep and cattle raisers. And everywhere it was used the story of the original well repeated itself. Grown sheep recovered their health and lambs were born strong and sturdy, and Michigan again became a wool-raising and wool-manufacturing state.

But it proved to be a literal casting of our pearls before swine--or rather sheep. For there was another side to the shield not at all so cheering. Ever since the dawn of history there has been known in the human family a curious disease marked by striking overgrowth and enlargement of the great gland in the front of the neck. This gland is called the thyroid, from the Greek word meaning "shield," because it lies just below and on either side of the great voice box, or Adam's apple, whose cartilaginous or gristly sides are supposed to resemble the triangular shield of the Greeks. It is probably one of the oldest diseases on record, for the good and sufficient reason that it does not require crowding together in villages or cities to develop it, but on the contrary is an affection chiefly of remote mountain valleys. Also, a goiter the size of a muskmelon hanging under a man's chin is enough to catch the dullest eye.

An Important Discovery

The disease was named goiter from the French word for throat, which we have still preserved in our word "gullet." Though it is really a great pity that the far more graphic and understandable terms of "big-neck" in English and "Kropf", or "crop," in German were not adopted instead.

For literally thousands of years goiter was merely one of the curiosities of medicine, for the reason it occurred chiefly in remote mountain valleys and that only the hugest and most tremendously overgrown cases were noticed. And these there was no use worrying about, because they were incurable by the clumsy surgical methods of the day and produced comparatively little disturbance of health or shortening of life.

But one day, scarcely more than half a century ago, it was rather suddenly discovered that certain forms of depression and chronic nervousness in middle-aged women with pasty faces, dull eyes, ashy complexions, thin greasy hair, and a mental state of great depression and apathy, were due to wasting away of this thyroid gland after the change of life; and what was much more interesting, they could be cured completely by feeding the patients with extracts of the thyroid glands of animals.

So recent in fact was the discovery that the death has just been reported, due to old age, of one of the first patients who was recognized and put on the thyroid treatment.

The old lady had been kept alive and in excellent health by a steady daily dosage of, in the first place, sandwiches made of the raw gland, and later prepared extracts of it, for nearly forty years, in the course of which time she was estimated to have devoured the thyroid glands of something like nine hundred sheep. Incidentally, the patient far outlived the doctor who had put her on the treatment, illustrating the well-known medical aphorism that the best way to live forever is to get a chronic disease and then sit down and take care of it.

A second finding, almost within a decade or so of the other, was that there was another form of goiter, marked by enlargement and overgrowth of the thyroid gland instead of shrinkage, recognized by protuberance of the eyeballs, hot and cold flushes all over the body, warm sweats, and incredibly rapid pulse, reaching in some cases 180 beats a minute. And what challenged our attention was that instead of lasting for years without appreciable harm to the health, it produced an extremely serious illness, with a death rate of nearly 20 per cent within two or three years. This came to be known by the graphic and descriptive title of exophthalmic--or out-eyed, "pop-eyed," goiter, on account of this protrusion of the eyeballs.

These two goiter harpoons waked us up to begin a systematic study of the condition of the thyroid gland at all ages, which culminated about ten or fifteen years ago in the astonishing and disquieting discovery that all over the great middle belt of this country, and not only there but all over Central and Western Europe, from 20 to 60 per cent of our young boys and girls of high-school age had mild degrees of enlargement of this gland. We had literally been taking food out of our children's salt and feeding it to sheep.

Here was literally a pretty kettle of fish, or rather a kettle without fish, as we shall see later, and we were for a time fairly stunned with this extraordinary and apparently menacing state of affairs. But we were not long in finding a clew. About fifteen years ago, while analyzing and studying in the laboratory this curious gland which had leaped so suddenly into the limelight, it was discovered that it differed from all other tissues of the body chiefly in the fact that it contained appreciable quantities of iodine. We all know iodine as we do the back of our own hands, as the saying is--that dark-brown liquid which stains our skins so deeply and which comes out of the family medicine chest to be painted over cuts and scratches and swollen joints and enlarged glands and has such a pungent smell. Also, probably most of us know, as a hazy recollection from our high-school days, that it is found in sea water and seaweeds, and with its sister element, bromine, is largely responsible for the bitter nauseous taste of a mouthful of old ocean which goes down our throats when bathing in the surf.

This caught our eye at once; but the amount of iodine was so tiny--scarcely more than three--quarters of a grain, or as much as would fit on the point of a penknife blade, in the entire gland--that it seemed absolutely incredible that a mere half pinch of any element could possibly produce such extraordinary effects upon the whole human body. But it set us thinking; and when, now scarcely more than five years ago, the active principle, or "soul," of the thyroid, thyroxin, was extracted and isolated by Kendall, at the Mayo brothers' laboratory at Rochester. Minnesota, and it was proved by actual demonstration that doses of a few thousandths of a grain would cure myxoedema, or the pasty-faced underthyroidism of women, and turn an idiotic dwarf called a cretin into a comparatively normal child of three or four. and that three-quarters of this thyroxin was iodine, we began to sit up and take notice. If a mere fraction of a pinch of this bitter brown sea salt could do things like this in disease, what might not its importance be to the human body in health?

This sent us back on a second search to see how widely spread over the system iodine was. And, as we had suspected, the infinitely delicate and responsive tests of modern laboratory science showed that every tissue and every part of the body contained its tiny percentage, or rather per thousand age, of iodine. To paraphrase Scripture, we live and move and have our being in extremely dilute solutions of iodine; which is simply another way of saying that we are merely a skin full of sea water and that every cell in our body is a jellyfish swimming in brine.

This instantly raised the question in our minds, Where do we get iodine? In the sea water. Where don't we get goiter? Along the seacoast and the shores. Where don't we get iodine? Up in the mountain tops. Where do we get goiter? In the same places.

The whole problem of goiter or myxoedema, of cretinism and exophthalmia, seemed to resolve itself into a question of the presence or absence of a few pinches of iodine in our thyroids.

Studies were promptly made by geologists and chemists of the percentages of iodine in soils and drinking water all over the United States, and these findings compared with its percentage in sea water, showing that, in the language of the report, "Practically all the iodine in the world is in the sea." This is due to the fact that, like its inseparable companion, common salt, iodine is the most readily soluble of all the salts contained in our rocks and soils, which were mostly, of course, laid down under sea water. And as the dry land gradually rose up out of the ingulfing ocean, leaving more than three-fifths of its area still at the bottom of the sea, the first elements to be washed out of the soil of the low mountains and poured into the sea were iodine and salt.

This explains at once why it is that through all history goiter has been especially associated with but not entirely confined to high mountain valleys, beginning in the Alps and the Apennines and Carpathians, and including the Atlas Mountains of Northern Africa, which were the cradle of the white race; and of late, as shown by McCarrison's interesting studies, the Himalayas and the mountains of Tibet.

These mountain valleys are in the first place a long distance from the seashore, so it was impossible for them to renew their supply of iodine by the method we shall discuss later. Also, having their strata more sharply tilted so as to allow drainage, they have been washed more completely free of their iodine and salt. A pinch of iodine is as important and vital in human life as the proverbial grain of salt.

It also comes home to us directly and solves our perplexing puzzle over why our great and fertile Mississippi Valley area and Great Lakes belt, or zone, though as innocent of mountain ranges of any sort as a lizard is of feathers, should show such an extraordinary flood of simple goiter. It is not necessary that you should live on mountains to get goiter, provided you are far enough from the sea and your soil has been sufficiently leached of all sea salts or covered by glacial drift which has naturally been "doublewashed." And how appallingly thorough has been that leaching and washing can be realized by the statement of the Geological Commission that an average human being would have to drink Lake Superior water steadily for forty years to get a sufficient amount of iodine for one yearly charge of his thyroid gland.

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