Vitamins and minerals are naturally very important for human health.

The following analysis is primarily about one essential micro-nutrient, namely iodine.

This essay is to raise awareness of iodine-deficiency, and not to encourage the indiscriminate consumption of seaweed or its products.


Iodine: disinfectant, deficiency, measurement, seawater, breathing, symptoms, warnings, advice, nutrition




Covid-19: co-morbidities




Iodine History and Geography:

Iodine was first discovered and isolated in 1811 after mixing burnt seaweed with sulphuric acid in the preparation of gunpowder. It was so named in 1814.

In nature: iodine is mostly bound to another element as a salt e.g. potassium iodide or potassium iodate.

Commercially: iodine is mined and exported from nitrate mineral deposits in the Atacama Desert in Chile; it is also extracted from oil-well brine solutions in America and Japan; and it has been extracted from seaweed in Japan.

In the laboratory: iodine is a re-active solid and vapourises easily. At ordinary room temperatures iodine vapour is blue-violet in colour with an irritating odour.

The Iodine Cycle

Iodine is released from the sea into the atmosphere, and it falls with rain onto the land. It is easily washed out of soil, particularly in mountainous areas with high rainfall.

Iodine is concentrated in various marine life - especially seaweed, shellfish, crabs, and haddock. Where food crops are grown in iodine-deficient soil, human development can be retarded unless iodine is added as a supplement.

In humans: iodine is found in stomach mucosa, in salivary glands, in the thyroid gland - and additionally in the female mammary glands.

It is present in both organic and inorganic form, and it is necessary to maintain a balance – in susceptible people too much iodine can be as bad as too little.

The highest concentration of iodine in the human body is found in the thyroid, which contains 70–80% of the total iodine content (15–20 mg). Muscle and eyes also contain high iodide concentrations. [5b] See the Reference List at the end.

For saliva: a concentration of iodine between 0 and 300 μg/100ml has been reported, with a mean concentration of 10 μg/100ml. After oral ingestion of potassium iodide, inorganic iodine can appear in saliva in 15 minutes. [6]

It has been reported recently that the Covid-19 infection first appears in saliva:

The salivary glands are the first place in the body that the virus infects.

It seems people become positive in their saliva before the rest of their breathing tubes.

Iodine as a Disinfectant:

Iodine has been used as a powerful disinfectant against bacteria and viruses.

Iodine has a germicide action due to its capacity to penetrate quickly through the cell wall of microorganisms, causing a rupture in the structures of its proteins and nucleic acid.

Lugol's Solution: a disinfectant comprising elemental iodine (5%) and potassium iodide (KI, 10%) with distilled water.

Originally used as a cure for tuberculosis, dating from 1829. Total iodine content: 130 mg/mL.

Tincture of Iodine disinfectant solution: elemental iodine (2.5%) and potassium iodide (KI, 2.5%) with ethanol 89%. Dates from 1908.

Povidone-iodine disinfectant: a mixture of elemental iodine and povidone (a polymer) with hydrogen iodide. Dates from 1955.

Tincture of Iodine (2%) has been used by travellers and explorers as a drinkable disinfectant for water-sterilization at 5 to 10 drops per litre of water.

Iodine is a disinfectant-of-choice for NASA space missions where it is has been used for water-purification systems in Skylab and the Space-station.

Iodine-based disinfection of water has a long history: iodine in concentrations between 2.5 - 7 mg/L (= parts per million, ppm) has been used for potable water treatment since the early 1900s especially for military operations (Hitchens, 1922; Vergnoux, 1915). Tablet formulations have been used since the 1940s to ensure the safety of drinking water for troops deployed in the field (Chang and Morris, 1953).

Also, in more recent times, iodine (and bromine) has become attractive for particular applications. Elemental iodine is used, for example, as a drinking water disinfectant aboard space vessels at a residual concentration of around 2 ppm (Atwater et al. 1996). [4]

Lugol's Solution, well-diluted with water or milk, has been listed in the British National Formulary (1993 edition) as an oral medication to be taken 3 times a day. [4a]

The European Union (EU) banned the sale of these iodine disinfectants from 25 October 2009.

Other Medical Uses of Iodine

An iodine preparation has been routinely injected into selected patients in hospitals e.g. to make the blood vessels stand out clearly in X-Ray charts (Radiography). It is also used for a cardiac prescription medication, amiodarone.

Radiographic contrast media [and amiodarone] can contain much more iodine than daily requirements, 75 mg and 320–370 mg, respectively. [5]

In regions of iodine-deficient soil and food-crops, iodine has also been injected into humans (as iodised oil) in iodisation health programmes.

For example, 2 million injections took place in Nepal in 28 remote northern regions using Lipiodol (1 ml of Lipiodol contains 480 mg of iodine).

A single 1-ml injection gave protection against iodine deficiency for 4 years.
Ref: Human Nutrition and Dietetics p548,p552

Iodine Deficiency:

The preferred method to combat iodine deficiency is to encourage the use of iodised salt in domestic cooking. The iodine is added to table salt as KIO3 (potassium iodate) or KI (potassium iodide).

Government programs for supplementary iodisation have created legislation (or regulations), and the implementation of the legislation can be voluntary (e.g. in many European countries and the USA) or mandatory.

As well as iodised salt, some countries will also legislate for the use of iodised bread flour and iodised vegetable oil in processed foods.

The amount of iodine added to salt can range from 5 to 100 μg/gm (5 to 100 ppm), depending on Government strategy e.g. Belgium and Denmark started on the low end and worked up, Chile started at the high end and worked down.

The dietary Recommended Daily Allowance (RDA) of iodine is typically 150-micrograms (150 μg).

A monthly amount of the RDA is very small and hardly bigger than a pin-head.

150 μg x 31 days / the density of iodine 4.933 gm/cc = a volume of 0.94 cubic millimetres.

(Some sources state that the RDA refers to the ingredient potassium iodate or potassium iodide rather than iodine itself, in which case the amount of iodine is reduced by 23 %.)

In Japan (a big consumer of seaweed) iodine intake has been estimated at 1 to 3 milligram per day – up to 20 times the RDA.

Certain foods called goitrogens and the way they are cooked can interfere with human iodine uptake and create an iodine deficiency (e.g. maize, cassava, lima beans, cabbage, peanuts, broccoli, kale, garlic).

The usual recommended level for the population's mean intake of iodine is 100-150 μg/day. This level is adequate to maintain the normal thyroid function that is essential for growth and development. In the presence of goitrogens in the diet, intake should increase to 200-300 μg/day.

Ref: Human Nutrition and Dietetics p547 [5a]

For populations with a naturally high iodine intake, these same goitrogenous foods can be used to suppress the excess:

While seaweed makes up to 10 per cent of the Japanese diet, seaweed is traditionally eaten in combination with vegetables such as broccoli, cabbage and soya, which inhibit iodine uptake by the thyroid gland.

A staple food in Japan and South Korea is called miso. One variety is a blend of soya and seaweed.

Iodine circulates around the human body, reaches almost every cell, and is excreted in urine.

The recommended daily intake (RDA) of 150 μg of iodine is reckoned to produce 100 μg/L of iodine excreted in urine.

A country's Iodine-Deficiency Deficit (IDD) is assessed by taking urine samples from school-children and some females. The results appear in tables published by the World Health Organisation (WHO). [7]

Iodine-Deficiency tables are also published by special-interest groups such as the Iodine Global Network (IGN): [8]

Caution is advised when using the IDD data. There appears to be at least two serious drawbacks concerning the measurement, and assessment, of iodine deficit disorder – these are sampling and statistics.

There is a requirement for a national large-scale survey of iodine supply in pregnant women in the UK to confirm the initial findings from relatively small samples. There are some indications that UI concentrations in young UK schoolchildren are adequate. However, this group usually consumes the largest amount of milk and its iodine status cannot be used as a proxy for the adult population. [9]

Sub-national UIC surveys are commonly carried out to provide a rapid assessment of population iodine status, but due to a lack of sampling rigor, they may over- or underestimate the iodine status at the national level and should be interpreted with caution...

Many countries monitor iodine status in both school-age children (SAC) and in women of reproductive age (WRA) or adults. WHO defines adequate iodine intake in adults as a median UIC value ≥100 μg/L. However, the scientific basis for this threshold is weak. Estimates based on populations other than SAC should be interpreted with caution. [8]

For any country, the WHO definition of an 'adequate' iodine intake uses a median value of 100 μg/L in the urine tests, and that means (by definition) that 50 % of the population-sample will have less than 100 μg/L, and hence be deficient in iodine.

Measurement and Testing for Iodine:

Comprehensive details describing the implementation of urine tests have been published by WHO here: [9a]

A detailed review, from 2011, of the many differing ways of measuring iodine in biological samples appears here: [9b]

In Nigeria, a low-powered nuclear reactor has been used to measure iodine in local foods: [10]

The complicated and time-consuming laboratory urine tests using wet chemicals described in the older literature (with a potentially explosive side-effect) have been improved with newer technology e.g. mass-spectrometry methods can be quicker, easier, cheaper and more accurate. [10a]

Iodine in Seawater, Sea Air, and Seaweed:

One particularly sensitive mass-spectroscopy method developed in 2019 has been used to measure the iodine content of seawater and iodised salt:

The suitability of the method was demonstrated through its application to the analysis of several types of samples, including seawater samples taken at different locations along the Spanish Mediterranean coast and some domestic iodized salts.

According to the results obtained, the method developed is rapid, easy to apply and to be automated, avoids sample treatment and requires only few microliters of sample. Furthermore, it has a low detection limit and allows the quantification of inorganic iodine over a wide concentration range. [10b]

From that research: a greater concentration of iodine was found in seawater close to the beach (sampled 2 metres away) than in seawater sampled 1-kilometre further out.

Other research shows that the concentration of iodine in seawater is greatest in tropical warm waters:

We have compiled the available measurements of sea surface iodide to produce a data set spanning latitudes from 69°S to 66°N, which reveals a coherent, large scale distribution pattern, with highest concentrations observed in tropical waters. Relationships between iodide concentration and more readily available parameters (chlorophyll, nitrate, sea surface temperature, salinity, mixed layer depth) are evaluated as tools to predict iodide concentration. Of the variables tested, sea surface temperature is the strongest predictor of iodide concentration. [10c]

As well as from food, iodine can be absorbed into the body by breathing iodine-enriched air.

Iodine is liberated from seawater and sea-spray by the action of sunlight:

Iodide ions are oxidised by sunlight to elemental iodine, which is volatile, so that every year some 400,000 tons of iodine escape from the surface of the sea. The concentration of iodide in seawater is about 50-60 μg/litre; in the air it is approximately 0.7 μg/cubic-metre.

Ref: Human Nutrition and Dietetics p535 [5a]

Research from 1984 into a maritime source of atmospheric iodine:

For the first time a simulating experiment proved that the intensity of iodine transfer with aerosols from seawater into the atmosphere is 110 times that for Na. It is hypothesised that organically bound iodine present in seawater may play an essential (or even the leading) role in iodine enrichment of aerosols. [11]

Health benefits have been observed by breathing iodine released from seaweed:

Iodine deficiency is known to result in deficits in neuropsychological development in children born to iodine deficient mothers. However, a remedy in terms of iodisation of table salt as is the norm in most countries, has not been embraced by Ireland. The borderline iodine status of the Irish population persists unchanged over the past 20 years with the annual median urinary iodine (UI) varying from 62.9 to 105 μg/L; overall median 72.4 μg/L (WHO recommended 100 μg/L).

Exposure to a seaweed rich environment allowing for intake by respiration of seaweed derived gaseous iodine, rather than simple proximity to the sea, confers advantages in terms of iodine intake with 21/46 (45.6%) of schoolchildren in seaweed rich coastal areas having UI values > 150 μg/L compared to 1/28 (3.6 %) and 2/93 (2.2%) in low seaweed abundant coastal and inland areas respectively. The corresponding values for adult females were 31/72 (43%), 7/60 (11.6%) and 21/132 (16.0%). The findings support introduction of iodine prophylaxis through Universal Salt Iodisation (USI), to ensure that women of child bearing age have access to sufficient dietary iodine. [12]

An earlier study from Ireland concerning breathing iodine in sea air especially near seaweed: [13]

A quoted value of iodine in sea air, 0.7 μg per cubic-metre, is much less than the concentration considered harmful, 1 mg per cubic-metre.

The countries whose populations eat most seaweed (and seaweed products such as miso) include Japan, S.Korea, China and Indonesia.

The reported health benefits of a seaweed diet in Japan include longevity, and some lower cancer-rates.

On a population level, those people for whom seaweed is a regular part of their diet, most notably in Japan, have dramatically lower rates of Breast Cancer (Hebert and Rosen 1996; Kodama et al. 1991). [14]

Regular seaweed consumption has in some instances been associated with concerns over toxicity, ingestion of contaminants, heavy metals, and intake of high levels of iodine. However, seaweed is widely present in the Asian diet, and it has been found to have health benefits and possible benefit against chronic diseases, such as cardiovascular disease, cancer and diabetes, according to observational studies in South East Asia. [14a]

Some statistics:

TABLE 1 The top five most densely-populated territories in the world, in order, with their associated Covid-19 recorded Cases and Deaths:










Macao (China)






5.8 million




Hong Kong (China)

7.4 million









14 million



Combined population: 14 million, with just 185 reported Covid-19 deaths (stats: December 2020).

The country population statistics are available from various sources e.g.

Covid-19 Cases and Death statistics are available here:

By way of contrast, some inland cities:



Covid-related Deaths


7 million



9 million



11 million



2 million


Population statistics are available here:

Google was used to find the Covid-19 city deaths (July 2020).

There appears to be a large statistical discrepancy in operation.

Various factors will be involved e.g. the wearing of face-masks, under-reporting of deaths, small regional boundaries.

This essay looks at an alternative idea - iodine.

The top five most densely-populated territories in the world are all located very close to the sea.

Q. Can an onshore breeze bring a low-level of beneficial iodine released from seawater ?

TABLE 2: Countries, Covid-19 Deaths per Million (July 2020), and food-Iodisation:




















































mandatory (see ***)




















mandatory + seaweed




mandatory + seaweed




+ seaweed




+ seaweed

New Zealand



mandatory + seaweed (see here)




mandatory + seaweed (see here)




mandatory + seaweed

Sri Lanka




*** For Denmark, a follow-up study 11 years after mandatory iodine fortification of salt was introduced in 1998 noted that the amount of iodine added was too low.

Iodisation sources for Table 2: table 3.2 [20] [14b]

The same countries using statistics from 5 months later:

TABLE 3: Countries, Covid-19 Deaths per Million (December 2020), and food-Iodisation:








































































mandatory + seaweed




mandatory + seaweed




mandatory + seaweed (see here)




+ seaweed




+ seaweed

Sri Lanka




New Zealand



mandatory + seaweed (see here)




mandatory + seaweed

Iodine deficiency has been recognised and reported for many years.

The following extracts suggest that an iodine deficiency deficit (IDD) in Europe and some parts of the world is still ongoing:

Iodine insufficiency remains a public health problem [in Europe] in 25 countries with a total population of about 683 million people. [16]

... about 50% of Europe remains mildly iodine deficient, and iodine intakes in other industrialized countries, including the United States and Australia, have fallen in recent years. [17]

Most iodine is found in oceans and most continental soil and ground water is deficient in iodine. Therefore, around 2 billion individuals are estimated to have insufficient iodine intake and are at risk of iodine deficiency disorders. [18]

Iodine Deficiency Disorders are a major public health problem worldwide affecting all groups of people of which children and lactating women are the most vulnerable categories. At a global scale, approximately 2 billion people suffer of iodine deficiency (ID) of which approximately 50 million present with clinical manifestations. [19]

1.2.3 Sustainability of salt iodization programmes:

The prevention and control of iodine deficiency is a continuous process. It requires monitoring to be sustainable. There are many examples throughout the world where iodine deficiency has re-emerged as a public health problem, where once it was under control. But it is in Europe where the problem is most dire. Overall, Europe has had the lowest salt iodization rate of all the WHO regions. [20]

The results of the questionnaire showed, firstly, that salt iodisation (in Europe) is mandatory in 13 countries and not mandatory in 21 ...

This represents at least 400 million people living in countries with no mandatory legislation for iodised salt.


The most populous countries in the region are France, Germany, Italy, Spain, Turkey and the UK, with a combined population of about 390 million, i.e. two thirds of the whole area. Only 2 of these countries (Italy and Spain) have iodisation legislation, which is not always adhered to. In contrast, all but 2 of the countries (Spain and the UK) have national monitoring.


Moderate-to-severe iodine deficiency still existed in 27.8% of the Turkish population in 2007, which was much better than in 1997 and 2002.

In the UK, iodine deficiency has emerged as a public health issue following several decades of apparent iodine sufficiency. [21]

Approximately one third of the world’s population lives in areas where natural sources of iodine are low, and therefore they require the permanent presence of iodine-supplying interventions. Approximately 29.8% (241 million) school-age children globally are estimated to have insufficient intake of iodine.

Many of these 241 million children live in the World Health Organization (WHO) South-East Asia Region (76 million) and African Region (58 million). [21a]

However, many other parts of the world do not have enough iodine available through their diet and iodine deficiency continues to be an important public health problem globally. Approximately 30% of the world's population remains at risk for iodine deficiency.

Iodine deficiency was once a problem in Australia and New Zealand, but with a remedy - adding iodine to bread flour:

The mandatory fortification of bread with iodised salt was introduced in Australia and New Zealand in 2009. Further details may be found here: Consumer → Nutrition and Fortification → Iodine

Sri Lanka introduced mandatory iodisation of salt in 1995:

In 1995, the government of Sri Lanka launched “Universal Salt Iodization” (USI) programme. With the strong private-public partnership and financial and technical support from external development partners, the Ministry of Health intensified the USI. In order to legalize the implementation of salt iodization programme, the government has passed a law that regulates the production and distribution of iodized salt in the country. This was incorporated into the Food Regulation Act, which came into effect in July 1995. Regulation under this act prohibited the production, distribution and sale of non-iodized salt for human and livestock consumption. The iodine content of salt at the retail level was specified to be within 25.0-50.0 ppm in 1996 in the legislation. In 2005, this law revised highlighting the minimum level of 15.0 ppm and the maximum of 30.0 ppm of iodine content in salt. [45]

Selected countries having iodine deficiency:


A serious UK iodine deficiency in 2011 was highlighted by the medical profession:


These data are coherent with recent epidemiological studies showing that some regions in our country are still characterized by mild iodine deficiency and a high frequency of goiter and other iodine deficiency disorders. This implies that further efforts should be made to successfully correct iodine deficiency in Italy. [22]

Despite this trend, a substantial proportion of the salt is sold un-iodized, most likely because consumers are unaware of the health benefits of using iodized salt, and also because of the higher price (+20% on average) of iodized salt due to higher production costs. [23]


Spain was considered iodine-deficient until 2003. Although iodine urinary levels have been in the optimal range in Spain since 2004, the WHO recognizes that our country does not meet the necessary requirements to ensure that the whole population is not at risk of an iodine deficiency disorder. The aim of this article is to review the current iodine status in Spain. Data from several studies emphasize the low consumption of iodized salt at home. [24]


Mild iodine deficiency (MID) is a long-standing problem in Belgium and was recognized only recently as a public health issue by the Ministry of Health …

The Belgian health authorities adopted a selective strategy to optimize iodine intake through the fortification of bread with iodized salt. A progressive, step-by-step increase of the iodine content of salt was chosen in order to minimize the incidence of hyperthyroidism. [25]


This pilot study suggested a high prevalence of iodine deficiency during pregnancy. Daily supplementation of 150 µg iodine from 20 GW might be insufficient to reach maternal iodine adequacy. [26]


In Portugal, a national representative study conducted among pregnant women in 2010 indicated an iodine status well below the WHO adequacy interval recommended for this population (150–249 µg/L), reporting median urinary iodine concentration (UIC) values ranging from 50 µg/L in the region of Azores to 84.9 µg/L in continental Portugal. Another survey reported in 2012 that Portuguese school-aged children had a median UIC of 106 µg/L, which is within the adequacy interval of 100–199 µg/L recommended by the WHO for this population group. Nevertheless, it was highlighted that 47% of this young population had a median UIC below 100 µg/L. [27]


Austria was a classical endemic goiter country due to widespread and severe iodine deficiency with urinary iodine values of 35 μg/day and a goiter prevalence in pre-adolescent children of almost 50%. A first effort to improve this situation was made already in 1923 by establishing a prophylactic program with iodized salt but this program was discontinued a few years later due to economic and political turbulences. In 1963, however, iodized salt was introduced again by a law which set the iodization level at 10 mg KI/kg salt and said that this salt should be sold at normal prices to everybody, excepting those who specifically request salt without iodine. In surveys done in 1972 and 1978 a significant improvement of the situation was found with a reduced goiter prevalence in children of only 12%, while urinary iodine/g creatinine remained below normal with a mean of < 65,3 μg. Goiter prevalence in the population was still elevated, the sometimes huge goiters of previous decades and endemic cretinism had gone.

Considering this situation the Austrian Society of Nuclear Medicine proposed for many years the increase of the amount of iodine in salt to 20 mg KI/kg. It was partly the “fallout” of the Tschernobyl accident that the Austrian authorities became active again and wrote into a law the requested increase of salt iodization in 1990. [29]


In 1994, the World Health Organization proposed the main strategy for iodine prophylaxis, i.e. Universal Salt Iodization. In Poland, a new model of iodine prophylaxis was introduced in 1996; the model includes obligatory iodization of household salt and neonate formulas and recommendation to take an additional daily dose of iodine for pregnant and breast-feeding women. This model allowed for eliminating endemic goiter in schoolchildren, eradicating cretinism in mountainous areas, and markedly diminished thyroid and gastric cancer incidence. [28]


The strategy to combat iodine deficiency in Denmark seems to be working because the fortification led to increased urinary iodine excretion in (almost) all participants. However, the level of iodine fortification of salt is too low. [30]

Covid-19 Co-morbidities:

Question: What are the characteristics, clinical presentation, and outcomes of patients hospitalized with coronavirus disease 2019 (COVID-19) in the US?

Findings: In this case series that included 5700 patients hospitalized with COVID-19 in the New York City area, the most common comorbidities were hypertension, obesity, and diabetes. [31]

Adverse outcomes of COVID-19 seem to be associated with comorbidities, including hypertension, cardiovascular disease, and lung disease. [32]

Obesity-related conditions seem to worsen the effect of COVID-19; indeed, the Centers for Disease Control and Prevention (CDC) reported that people with heart disease and diabetes are at higher risk of COVID-19 complications. [33]

By contrast, a lower occurrence of obesity has been noted in Japan and South Korea. Both countries in general have a higher dietary intake of iodine. From a recent BBC item in 2020:

That's why the Royal College of Paediatrics and Child Health has described obesity as "one of the greatest threats" to children and society as a whole.

And these problems are not unique to England - with Scotland, Wales and Northern Ireland experiencing very similar levels. But around the world the picture does vary. Less than 10% of adults in South Korea and Japan are obese, compared to 40% in the US.

Iodine Deficiency Symptoms:

What are the symptoms of low iodine?

Putting on weight. One of the most noticeable signs of an iodine deficiency is unexpected weight gain.

As the body's iodine levels fall, hypothyroidism may develop, since iodine is essential for making thyroid hormone. While this is uncommon in the United States, iodine deficiency is the most common cause of hypothyroidism worldwide. [34]

The symptoms of hypothyroidism vary widely; some people have no symptoms, while others have dramatic symptoms or, rarely, life-threatening symptoms. The symptoms of hypothyroidism are notorious for being nonspecific and for mimicking many of the normal changes of ageing.

Hypothyroidism weakens the respiratory muscles and decreases lung function. Symptoms can include fatigue, shortness of breath with exercise, and decreased ability to exercise.

Treatment with thyroid hormones largely reversed both the taste and smell defects. In one patient, taste and smell abnormalities were completely corrected after 16 days of treatment with thyroxine. This study indicates that taste and smell defects are common clinical abnormalities in primary hypothyroidism, and suggests that these defects may contribute to the anorexia and lack of interest in eating which are frequently observed. [34a]

Hypothyroidism has been recognized as a cause of secondary hypertension.

Today diabetes is grouped in two main forms: type 1 and type 2 diabetes. Both type 1 and 2 diabetes can occur in people diagnosed with Hashimotos and an underactive thyroid.

People with prediabetes and low thyroid function were more than twice as likely to progress to full-blown type 2 diabetes compared to those with normal thyroid hormone levels in a new study,1 published in the journal, BMC Medicine.


Japanese iodine intake from edible seaweeds is amongst the highest in the world. Predicting the type and amount of seaweed the Japanese consume is difficult due to day-to-day meal variation and dietary differences between generations and regions. In addition, iodine content varies considerably between seaweed species, with cooking and/or processing having an influence on iodine content.

Due to all these factors, researchers frequently overestimate, or underestimate, Japanese iodine intake from seaweeds, which results in misleading and potentially dangerous diet and supplementation recommendations for people aiming to achieve the same health benefits seen by the Japanese. By combining information from dietary records, food surveys, urine iodine analysis (both spot and 24-hour samples) and seaweed iodine content, we estimate that the Japanese iodine intake--largely from seaweeds--averages 1,000-3,000 µg/day (1-3 mg/day). [35]

Seaweeds are increasingly consumed as part of the diet, both in New Zealand and other parts of the world. Some seaweeds are consumed in greater quantities than others. The brown seaweed U. pinnatifida (wakame) for instance, is eaten in soups and stews like a vegetable, and therefore up to 10 g dry weight, or more, could be consumed per serving. The other brown seaweeds, M. pyrifera, E. radiata and H. banksii, are used as seasonings and therefore would seldom be consumed in quantities of more than 1 g dry weight.


None of the seaweeds studied would deliver harmful quantities of heavy metals in the quantities that they are commonly consumed. Seaweeds contain an array of valuable minerals and carbohydrates with potential health-promoting effects. Alongside other fruit and vegetables, seaweed can contribute to a healthy balanced diet. [36]

A national survey of 521 Australian consumers was conducted. About 75% of respondents had eaten seaweed; however, only 37% had consumed seaweed regularly over the past 12 months. [37]

Several minerals and trace elements are essential for normal thyroid hormone metabolism, e.g. iodine, iron, selenium, and zinc. [38]

Cooking reduces the iodine content of foods, with over half of the iodine escaping during boiling, whereas only about a fifth is lost in frying or grilling.

Ref: Human Nutrition and Dietetics p535 [5a]

Edible seaweeds are a rich and sustainable source of macronutrients (particularly dietary fiber) and micronutrients, but if seaweeds are to contribute to future global food security, legislative measures to ensure monitoring and labeling of food products are needed to safeguard against excessive intakes of salt, iodine, and heavy metals. [39]

A BBC item from 2011 drew attention to the benefits of eating more seaweed:

A connection between seaweed and a heightened sense of taste 'umami' is described here, with some very detailed notes on the history and production of flavour-enhancing glutamates including MSG (mono-sodium glutamate) from seaweed extracts: [39a]

Early B-&-W film of Japanese women collecting seaweed:

Some problems with Iodised Salt:

The main strategy for the control of iodine deficiency disorders (IDD) - salt iodization – was adopted by the World Health Assembly in 1993 and established as a UN General Assembly's Special Session on Children goal in 2002. Salt has been chosen as a vehicle because of its widespread consumption and the extremely low cost of iodization. However, where the prevalence of iodine deficiency is high and where salt iodization is not feasible, the alternative is to administer iodine directly, either as iodide or iodized oil, focusing on women and young children. [20]

At community level, we investigated reasons of not using iodized salt in cooking, whereby more than 40% responded that the restricted mobility and difficulty in reaching big hypermarkets were the main reasons for low consumption of iodized salt... [40]

The problem of iodine deficiency in European countries has been greatly underestimated for several decades, and so salt iodization programmes have suffered.


A few European countries require iodized salt in food processing but most do not.

So far, only Denmark, Germany, the Netherlands and Switzerland have ... amended their regulations accordingly.


Many of the remaining problems with regard to iodine deficiency in European countries are due to inadequate controls on imported salt and a lack of resources for monitoring salt iodization effectively. The most important factor, however, is the lack of a clear commitment from governments, and ultimately, an insufficiently strong consumer demand for iodized salt.


The packaging of iodized salt is very important. To avoid losses as high as 75% over a period of nine months, waterproof packaging is required... [20]

Some cultural influences can account for a lower iodine intake e.g. a decline in eating fish on Fridays, the closing of fish-and-chip shops, and using less salt for dietary and hypertension reasons.

A remarkable piece of research was undertaken in 2016 in response to the supply of five-holed salt shakers, offered free of charge by local government, to all independent fish-and-chip shops in the area of Gateshead in the North East of England, in 2006.

It had the objective, among other things:

"To determine if the amount of salt delivered by standard salt shakers commonly used in English independent takeaways varies between those with five and 17 holes"

The experimental design considered 4 independent variables:

- type of shaker used (5 or 17 holes)      NB: 5-holed salt shaker = 5HSS, 17-holed = 17HSS
- amount of salt in the shaker (shaker full, half-full or nearly empty)
- time spent shaking (3, 5 or 10 seconds)
- the person serving.

Summary of results :

This is the first documented study we are aware of exploring differences in salt delivered by salt shakers commonly encouraged in independent takeaways in England. We compared the standard 17HSS to the newer 5HSS. Across all experiments, the 5HSS delivered around 34% of the salt delivered by the 17HSS. This difference was robust to changes in the starting fullness of shakers, the length of time spent shaking and the person serving. [44]

There is no mention in that research on the type of salt (iodised or non-iodised) being used in the experiment, and no mention at all about a serious iodine deficiency in the UK.

There are problems in actually buying iodised salt in the UK. Most corner-shops and high-street supermarkets do not sell iodised salt. In the writer's experience only a local Waitrose supermarket has iodised salt on its shelf.

Prices: normal salt: 40p per 750 grams, iodised salt: £1.00 per 400 grams.

A price difference of 500 %.

In Australia (Perth), iodised salt is common-place and there is no price difference compared to normal salt.

A 400-gm tub of iodised salt bought several years ago in the UK carries a label stating:

It contains Potassium iodate to give an iodine content of not less than 1150 micro-grammes per 100g.

2g of Iodised Table Salt provides at least 15 % of the RDA of Iodine.

The same product bought more recently in 2020 has a slightly re-worded label:

... Iodised Table Salt contains Potassium iodate to provide a source of Iodine.

A 1.5g portion provides at least 20 % of the daily Reference Intake of Iodine ...

Nutrition Information: Iodine 2000 μg per 100 g.

It appears that the newer item has a much-increased iodine concentration: up from 1150 to 2000 μg per 100g, with a suggestion that less salt is expected to be used: a daily 2g portion reduced to 1.5g.

Monitoring Iodine and Providing Advice:

The International Council for the Control of Iodine Deficiency Disorders (ICCIDD) first met in 1986 in Kathmandu, Nepal.

The World Health Organization proposed a scheme called Universal Salt Iodization in 1994.

A Network for Sustained Elimination of Iodine Deficiency (NSEID) was formed in 2002 at a U.N. Special Session for Children.

The ICCIDD Global Network was formed from the ICCIDD and NSEID in 2012 and later renamed the Iodine Global Network (IGN) in 2014:

The UK Iodine Group was formed in 2012:

The World Iodine Association was formed in 2015:

Reminders about iodine deficiency appear from time to time issued by the IGN, such as this newsletter article dated 18 August 2017:

Even moderate deficiency, especially in pregnant women and infants, lowers intelligence by 10 to 15 I.Q. points, shaving incalculable potential off an individual's or an entire nation's development. Places like Israel and the UK count many women at risk of developing health problems in themselves such as thyroid dysfunction or more importantly in their offspring if they do not have adequate iodine intake prior to and during pregnancy.

In France, for example, they don't even allow the use of iodized salt in any processed foods, thereby neglecting the population of a potential source of iodine.

And in another article, dated 2 November 2015:

... in 2005 the World Health Organization pointed to Vietnam as a model for success in salt iodization. But only three years later, their progress had taken a U-turn. Results of a nationwide household survey showed coverage had fallen by almost a third — more than 30 years of progress undone in five.

The Ocean Liner Diamond Princess had a Covid-19 outbreak in 2020:

A cruise ship, named the Diamond Princess, travelled from Yokohama on 20 January and included stops in Japan (Kagoshima), Hong Kong, Vietnam, Taiwan and Japan (Okinawa), before arriving back in Yokohama on 3 February. [15]

Total crew and passengers: 3,711 (2,666 passengers and 1,045 crew).

83% of the people did not get infected. Average age on board: 58.

The median age of the infected passengers was over 70. Total Cases 712, Total Deaths 13, Total Recovered 651

The research team estimated that 72% of people infected with COVID-19 on board the Diamond Princess cruise ship remained asymptomatic. For each asymptomatic case, it remained uncertain how infectious they were although they were unlikely to be as infectious as a symptomatic case.

As you might imagine, before they knew it was a problem, the epidemic raged on the ship, with infected crew members cooking and cleaning for the guests, people all eating together, close living quarters, lots of social interaction, and a generally older population.

Seems like a perfect situation for an overwhelming majority of the passengers to become infected. And despite that, some 83% (82.7% – 83.9%) of the passengers never got the disease at all … why?

83% of the passengers never got the disease at all … why?“

Was it because 48% of the passengers were Japanese nationals (with adequate iodine):

When the Diamond Princess returned to Yokohama, 2,666 passengers — including 1,281 Japanese nationals — and 1,045 crew members were aboard.

And could a cruise holiday in sea temperatures of 28 C with natural marine iodine vapours surrounding the ocean liner keep people a little bit more healthy ?

Some speculation concerning sunlight:

Vitamin-D and sunlight are associated with better health. Also associated with sunlight is iodine ... iodine is very light-sensitive.

This light-sensitivity is utilised in photographic chemicals such as sodium-iodide.

To prevent degradation, some iodine compounds are stored in dark-coloured glass bottles.

The sensitivity is due to some longer, visible, wavelengths (400-600 nm) of sunlight having sufficient energy to break an iodide bond and liberate iodine. The liberation of iodine from seawater by sunlight is noted earlier in the essay here.

These longer-wavelengths of sunlight are reported to penetrate a few millimetres of exposed skin, into the epidermis. [41]

Hormones from the thyroid gland - T3 (with 3 iodine atoms), and T4 (with 4 iodine atoms) - are found in the skin’s epidermal layer. [42]

Thyroxine (T4) from the thyroid gland is an organoiodine compound. The bond-dissociation-energy (BDE) of an organoiodine carbon-iodine (C-I) bond is given as 57.6 kcal/mol ( = 241 kJ/mol) at 25 C.

Applying a conversion formula: a BDE of 241 kJ/mol equates to an energizing wavelength of 497 nm capable of breaking the iodine bond.

Ej (Joules) = BDE (kJ/mol) * 1000 / Avogadro’s number.

Wavelength λ = Planck’s constant * speed of light (m/s) / Ej.

Simplifying: Wavelength λ (nm) = 119737 / bond dissociation energy E (kJ/mol)

Q. Can sunlight liberate small amounts of iodine from thyroid hormones in the skin, or even from the thyroid gland in the neck ?

In the same way that clear-glass passes sunlight and dark-coloured glass blocks sunlight, so fairer skin might allow more sunlight to pass than darker skin.

An historic treatment of an illness (tuberculosis) by exercising patients in open-air is described here:

The first German sanatorium for the systematic open-air treatment had been started by Hermann Brehmer (1826-1889) at Görbersdorf in Silesia in 1854. To start with it was a small group of cottages; ultimately it would grow to 300 beds. Brehmer advocated high altitude (it was at 518 m), abundant diet with some alcohol, and exercise in the open air under strict medical supervision. The results were regarded as highly successful, surpassing any previous treatment. [43]

It is not uncommon to find sanatoria located near a coastline.

The introduction of Lugol's Iodine Solution for the treatment of tuberculosis in 1829 is noted earlier in the essay here.

Some observations:

1. Countries which have historic iodine-deficiency show major problems with Covid-19.

2. Countries with a consumer diet high in iodine show fewer problems with Covid-19.

3. Common symptoms of Covid-19 - loss of the sense of taste and smell, breathlessness - are also symptoms of iodine deficiency.

4. Common co-morbidities associated with Covid-19 - diabetes, hypertension, obesity - are also symptoms of iodine deficiency.

5. An iodine mouthwash solution has been observed to kill the SARs virus in test-tube tests - and the SARs virus is related to Covid-19.

Here, we demonstrate in vitro virucidal activity of an oral PVP-I product against SARS-CoV-2, the virus causing COVID-19. [1]

(PVP-I is Povidone-Iodine, an iodine disinfectant.)

6. A major gender bias in serious Covid-19 infections has been reported: more males are affected than females …

In the UK, men with COVID-19 are more likely to need intensive care and they are more likely to die.

In the first week of April 2020, the UK Intensive Care and National Audit Research Centre (ICNARC) published a report on the first 2,249 patients admitted to intensive care in the UK with COVID-19.

It showed that in the 775 patients with full data, men with COVID-19 were more likely to die than women (53.2% v. 37.5%) and were over-represented among those needing mechanical ventilation (73% v. 27%) and basic respiratory support (71% v. 29%). [2]

7. … and there is a gender bias in iodine prevalence in humans: females have extra iodine in mammary glands.

Because infants are born with small amounts of stored intrathyroidal iodine, they depend on human-milk iodine for normal physical and neurologic growth and development. The mammary gland concentrates iodide; however, there is a lack of consensus on the concentrations of breast-milk iodine necessary to achieve equilibrium in the infant. [3]

Q. Does extra iodine give extra protection ?

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30-Dec-2020: Currently has dropped offline.

Deaths-per-million in Tables 2 and 3 are provided by the www source, and are calculated by dividing the number of deaths by the country's population expressed in millions e.g. 900 deaths / 21 million = 43 D-p-m.

Many of the extracts from online journals have spelling mistakes, and only a few have been corrected.

This essay was started in July and progressed until September. It was re-formatted in December. More points remain to be added.

From Iran, some research to indicate that low iodine levels may be linked with cancer:

To the best of our knowledge this was the first study to evaluate the iodine status in Iranian patients diagnosed with a malignancy. However, results of the present study showed severe iodine deficiency in the patients. Therefore, checking the status of iodine in normal populations and cancer patients may be crucial. In addition, we suggest that daily consumption of salt fortified with iodine or other approaches might be an effective strategy for prevention or reduction of malignancies. [46]

In a report from the UK Office For National Statistics (ONS): “Coastal towns have experienced lower rates of coronavirus (COVID-19) related deaths during 2020 than non-coastal towns".

A product using a non-iodine
extract (carrageenan, a natural polymer) from Red Seaweeds such as Carrageen or Irish Moss, to fight Covid-19:

A link to show sea-surface temperatures around the world:

Bangladesh: population 165 million, Covid-19 deaths-per-million 46.
Most of the country lies below 12 metres above sea-level, and it contains the world's largest mangrove forest.

A substance that overcomes the activity of a disinfectant is called an inactivation agent, neutralizing agent, or antidote. A neutralizing agent for iodine disinfectant is Polysorbate 80. [see 47] Polysorbate 80 is also used as an emulsifier in food products such as ice-cream, and other frozen desserts, in some canned vegetables, and has been used in numerous pharmaceutical items including vaccines, vitamin pills, and medications e.g. amiodarone.

To print this essay with yellow hiliting, in Print Options enable 'Background Colour'.