Lodine and the renaissance

Sanjay Kalra, Ambika Gopalakrishnan Unnikrishnan1 , Kaushik Pandit 2

Department of Endocrinology, Bharti Hospital and Bharti Research Institute of Diabetes and Endocrinology, Karnal, Haryana, 1CEO, Chellaram Diabetes Institute, Pune, Maharashtra, 2Chief Endocrinologist and Diabetologist, Belle Vue Clinic, Kolkata, India.

Department of Endocrinology, Bharti Hospital and Bharti Research Institute of Diabetes and Endocrinology, Karnal, Haryana, 1CEO, Chellaram Diabetes Institute, Pune, Maharashtra, 2Chief Endocrinologist and Diabetologist, Belle Vue Clinic, Kolkata, India

"The warm humour is lacking among them; their bodies are large, their natures gross, their manners harsh, their understanding dull, and their tongues heavy… The farther they are to the north the more …." "‑‑‑have not cultivated sciences…… they lack keenness of understanding and clarity of intelligence‑‑‑ [they are] apathetic" To the thyroidologist, these descriptions immediately conjure a mental image of cretinism, caused by iodine deficiency. While today's student would be hard‑pressed to pinpoint the geography being discussed, yesteryears' endocrinologists would immediately identify the Himalayas or the jungles of central Africa as the setting for these quotes. It is possible that physicians of the nineteenth or early twentieth century might suggest the Alps as a possible location. However, all groups of physicians would certainly find it difficult to justify the strong language used by the scholars quoted above.

These descriptions in fact, refer to northern Europe, and are penned by famous Arab pioneers. Mas'udi, the tenth century Arab geographer, describes the inhabitants of Urufa, as Europe was then known, in the first sentence (large bodies, gross natures, dull understanding, heavy tongues), while the next two quotes are from a 1068 book by Said ibn Ahmad, qadi of Toledo, Spain (then a Moorish city).[1]

It is proven beyond doubt, then, that western and northern Europe, which today lead the world in technological and cultural advancement, were, a mere 1000 years ago, considered primitive by their neighbours. Historians do agree that a fundamental change occurred in Europe somewhere between the years 1000 and 1500, which set the foundation for European supremacy in thought as well as deed. Experts, however, are unable to agree upon the reasons for this change.

A wide range of explanations has been put forward to understand the reasons for European leadership. These reasons can be classified as geographical, economic, and religious theories.[1] Geographical theories, propounded by Braudel and Mc Cormick, point to the unique physical nature of this small continent, which made development of tools, labor‑saving devices, and shipping a necessity for Europe Economic theories, as proposed by Abu Lughod and Needham, suggest that economic or intellectual collapse or stagnation in the East (China) created a global vacuum which was filled by Europe. Other economy‑based theories, advanced by North and Thomas, state that a sudden increase in population led to economic specialization, which in turn fostered trade and growth of economy. A third group of researchers feel that the Christian church played an important role in unifying, and strengthening European thought. All these suggestions, however, are limited in their approach, and are unable to actually explain why Europe did not develop before it did, why it remained backward as compared to the Middle‑East for so long, and why it did take off when it did.

In this editorial, we hypothesize a possible endocrine reason to help explain Europe's march to global dominance. We suggest iodine repletion achieved by the inter‑continental salt trade, as the catalyst which spurred the European awakening. As a disclaimer, we caution our readers that this is a hypothesis, and a highly speculative one at that‑ this editorial would come under the realm of being a literary take on history with an endocrine twist in the tale. It is meant to be read in a lighter vein, and is, we clarify, by no means an authoritative treatise on any subject!

Having said that, let us return to this somewhat provocative iodine hypothesis. Iodine is an essential micronutrient, which is obtained from sea food and salt. While inhabitants of coastal areas are usually able to maintain adequate iodine intake, the same may not be true of inland‑dwellers. Communities residing in mountainous and hilly terrains often suffer from endemic iodine deficiency. This public health challenge has been realized (and managed), in almost all continents: The Alps, the Himalayas, the Andes and the Congo river basin are a few examples of iodine‑deficient areas which spring to mind.

Lodine deficiency is often associated with altered cognitive function. The aim of this editorial is not to review literature on this aspect of thyroidology, which has been so comprehensively done by earlier stalwarts.[2] A recent meta‑analysis, too, has clearly documented the effects of iodine deficiency and supplementation on average intelligence in children.[3] We posit that early Europe was probably an iodine‑ deficient environment, and thus inhabited by an intellectually‑challenged population. Availability of salt allowed its population to shed the clinical characteristics of cretinism, and move towards building a more developed socioeconomic society, which soon began to rule the world.

Salt is an essential part of human diet. However, the amount of salt that we eat today is much higher than what previous generations consumed. In fact, there still exist primitive Amazon tribes which survive on a salt‑ free diet.[4] Iodized salt is also the main source of iodine today, and most readers will find it difficult to conceive of "iodine– less" salt today.

Yet, natural salt was a major source of iodine in earlier times. Though salt was not 'iodized' then, it contained many minerals including iodine. A precious commodity in ancient Europe, imported as rock salt from Asia, it was an expensive spice, available to few. Salt scarcity, and iodine deficiency, prevalent in central Europe, meant that cretinism was bound to be endemic. Reports and descriptions of physicians from the 16th to 18th century portray an accurate idea of the magnitude of this problem:[5] We can assume that the situation would have been worse five centuries ago, when central and northern European inhabitants would have had no access to salt.

Many economic factors must have coalesced with each other, about a 1000 years ago, to encourage trade. The opening of trade routes with Asia and Africa would have enhanced access to rock salt, which also contains iodine, and increased consumption of iodine rich sea food. The rise in iodine consumption would have helped reduce cognitive dysfunction, so elegantly described by Mas'u di and Said ibn Ahmad, and stimulate intellectual thought. This is turn would have encouraged sharing of ideas, creation of universities, expansion of trade links, opening of new trade routes and import of more iodine‑ rich salt. Thus, a virtuous cycle would be set in motion, fuelled by iodine repletion, and perhaps, euthyroidism.

The iodine hypothesis is strengthened by the temporal profile of a few seminal events. The land trade of salt, sourced from India and the Sahara Desert, had opened up early in the course of history. Salt gradually become more and more freely available to Europeans. At the same, the rivers of Europe began to be used for transport and trade, allowing freshly caught iodine rich sea fish to reach the hinterland in time for consumption. Both these factors served to increase iodine intake, and fuelled the intellectual awakening of Urufa.

Iodine is essential for the thyroid gland's function, and is also important in brain development. The linkage between thyroid function and intellectual performance is supported by modern evidence‑based evidence as well.[6] Improved intellect, combined by gathering together of the best brains in universities, could have been one of the several factors that led to the emergence of Europe as a dominating force in global matters.

The iodine hypothesis, of course, may not be the only explanation for the awakening that Europe experienced a thousand years ago. It is robust enough, however, to withstand scrutiny, and to encourage further scholarly research to address this question: Did Europe owe its eminence, at least in part, to biological or even endocrine, factors?

From an Indo‑centric perspective, this editorial provides food for thought and probably sparks yet another debate. As India transitions from iodine deficiency to iodine‑replete status, will the same circle of history come true for this nation? Can we be optimistic enough to assume that the next century will be the era of Indian awakening and dominance? As an answer to this question, we as editors can only write: Watch this space!


  1. Watson P. Ideas. London: Weidenfield and Nicolson; 2005. p. 319‑35.
  2. Reitan RM. Intellectual functions in myxedema. AMA Arch Neurol Psychiatry 1953;69:436.
  3. Qian M, Wang D, Watkins WE, Gebski V, Yan YQ, Li M, et al. The effects of iodine on intelligence n children: A meta‑analysis of studies conducted in China. Asia Pac J Clin Nutr 2005;14:32‑42.
  4. Kalra S, Sahay M, Baruah MP. Reducing salt intake, for a healthier world. J Med Nutr Nutraceut 2013;2:1‑2.
  5. Niazi AK, Kalra S, Irfan A, Islam A. Thyroidology over the ages. Indian J Endocrinol Metab 2011;15:121‑6.
  6. Taylor PN, Okosieme OE, Dayan CM, Lazarus JH. Therapy of endocrine disease: Impact of iodine supplementation in mild‑to‑moderate iodine deficiency: Systematic review and meta‑analysis. Eur J Endocrinol 2014;170:R1‑15.

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