VEGA looks at the iodine question, following publication of a recent Lancet paper
1. In the 1920s, the figures for intakes of iodine were confined mainly to those living near the sea and it was assumed enough nutritional supplies would be supplied by that amount. However, the classical cases of thyroid deficiency due to insufficient iodine supplies in the atmosphere still remained to some extent in the diets of midlanders (‘Derbyshire neck’) and they would be likely to arise in people such as vegans who even though they lived by the sea detested the taste of seaweed and suffered appalling Derbyshire neck.
2. There are also changes in farming methods and agricultural practices that might have contributed to supplies in milk and dairy produce. The changes were mainly caused by the feedstuffs given to housed cows during the winter and the use of iodophors and residues left in their rations.
3. Therefore we had to warn the general population, not only vegans, who may have missed the adventitious additions of iodine to the diets. Work we had been doing before with Professor Davies of Southbank University gave us an opportunity to clarify the position and we seized the opportunity of one of her students, tackling the problem in a PhD thesis, which was of general interest, but particularly to affected vegans.
4. Her findings and those of allied groups of researchers suggested that artificial cherries coloured with a red dye were likely to be a major source of iodine in the diet of such people and the colour that was used was erythrosine. Only later was it definitely analysed and proved to be a poor source of iodine of this kind and it was available in many human foods but not by vigorous pursuance of the vegan lifestyle; and there were other sources of red food colours, such as cochineal and synthetic azo dyes. The student chosen by Jill Davies was Helen Lightowler, who carried out a number of analyses and compared them with intakes, lifestyles and signs of deficiency diseases. These values confirmed the general impression we got with adult consumers that they might be adequate to reach the recommended intake of 150 micrograms but there would be borderline deficiency developing and prolonged deficiency if there was only this product available. There was also the possibility of medicinal inputs such as amiodarone but these were uncertain. Amiodarone did not lend itself to fragmentation in metabolism. It has four iodine atoms.
5. The remaining steady source was seaweeds. We therefore had to continue with seaweed in the traditional fashion and we had to look at seaweeds to discover the best source. Helen discovered the solution to this conundrum and looked at inputs and outputs which matched fairly closely. Different types of seaweed were found to deliver different amounts of iodine (from low in nori to high in kelp). Kelp tablets were found to be rich in iodine and acceptable to all parties including vegans. But they were more acceptable on grounds of taste and appearance in products than the raw ‘weeds’.
6. The supermarkets had produced various forms of raw seaweed in attractive form and sold in certain stores but the uptake was poor all round and they were withdrawn. So the iodine status of vegans became more serious unless they took supplements. One supplement was labelled with claims to iodine content but was in fact found to contain ten times the iodine amount that was given on the labels. Helen Lightowler got the analyses repeated to avoid an error in content. Eventually the product was reanalysed by the government research lab and Helen’s results were improved so the situation was corrected accordingly.
7. Subsequently, in 2004, Braverman published results from weeds which agreed with some evidence that Helen had, which confirmed the superiority of kelp tablets. Kelp can be obtained as tablets in healthfood stores but not everyone is getting an amount that would be sufficient. Subsequent work produced improved sources of seaweed and they could be well-represented on the table but the danger that was emerging for the public was a barrage of salt as an unacceptable part of the diet because of the effect on one of the five additives, to which the government takes exception. So the public is faced with a compromise in choice, so iodine might be good but salt not, because it is avoided in this country due to its effect on the circulation.
Kelp (Laminaria spp.), off Yorkshire coast
8. This conundrum continues and raises further doubts about the wisdom of failing to iodise bread made with commercial flour (which may also be done with potassium iodate). The contribution of unwise fortification of food has once again attracted attention and most countries now use iodised flour to add to bread but this process is applied only fitfully in specialist bread in this country and would be a separate issue to settle in government fortification of foods and labelling.
9. Therefore the dangers of fortification of baking flour must be weighed against possible benefit of iodine to the thyroid gland and various hormones. Babies, for instance, are a special case for when additives should be introduced to the mother and developing foetus. For the moment, therefore, the addition of iron to British diets provides some clues to the benefits and safety at all levels at birth and adulthood, but requires further work for safety. Meanwhile, VEGA has no other than to follow common advice from the WHO (World Health Organisation) and ICCIDD (International Council for the Control of Iodine Deficiency Disorders): 150 micrograms or more is added safely as a good guide and has been tested very widely in famine relief for adults and babies at birth; 250 micrograms is recommended for pregnant and lactating women. Now that further analyses are being done on erythrosine and other red dyes, their ability to contribute more certain supplies of iodine may be acceptable and more seaweeds may add to the complement and be used in a more determined fashion.
10. As a result, this should involve additions of iodine to the diet, cooking involving iodine-rich compounds on the basis of Helen Lightowler’s findings and iodine containing foods being developed in the world generally. We follow the guidance of the WHO and the ICCIDD and results from the ALSPAC (Avon Longitudinal Study of Parents and Children) study.
11. A reliable source of seaweed is laverbread, as supplied by Parson’s Pickles of Bury Port in South Wales (http://www.parsonspickles.co.uk), obtainable by post and in some shops. Various seaweed products are also obtained from some fishmongers and healthfood stores (eg the Clearspring brand). Analyses of laverbread (obtained from Parson’s Pickles and from other sources) suggest that about 30g of laverbread would supply the recommended adult intake of iodine. The iodine content varies from plant to plant. We have published recipes with seaweeds as ingredients. Seaweeds should be counted as one of the Five-a-Days.
12. Iodine is one of the halide elements, which comprise fluorine, chlorine, bromine and iodine, as well as some higher elements in the periodic table. They are interesting in that they are incorporated into plant foods by an oxidative process as well as the usual incorporation of iodide with a minus charge. Certain halogen elements are found in deep water plants and are not fully analysed, so they may occur in deeper oceans.
13. Sodium salts of iodine also have to be considered, though may be less suitable due to their volatility and liberation of iodine through free radical action. In earlier times, in the Vegetarian Society day plans, sodium/potassium ratios were quoted, which has certain advantages to this day.
Dr Alan G Long
See also: Food Sources of Iodine