Wednesday 18 January 2012

Iodine Deficiency Disorder (IDD)- Water Under the Bridge Article from Harvard Medicine (2004)- Points to BioLargo Opportunity

Water Under the Bridge
A neurologist turns to hydrology, agronomy, and veterinary medicine to tackle the world’s most preventable cause of mental retardation.

Link Here

As a young boy growing up in Indiana, G. Robert DeLong ’61 would toss sticks into creeks to gauge the speed of the water. Little could he have known how useful his childhood game would prove decades later, when he set out to eradicate a disease that for centuries had been devastating children in a remote corner of China.

DeLong traces his fascination with iodine deficiency disorders (IDD) to nearly 25 years ago, when his mentor, John Stanbury ’39, suggested that he join a medical trip to Ecuador. “I thought the reports would turn out to be exaggerated,” DeLong recalls. “But in a single month in an Andean mountain village I saw 120 cases of a disease that, until then, I’d only read about in textbooks. These were people in whom prenatal iodine deficiency—and the resulting fetal hypothyroidism—had caused cretinism, characterized by blighted physical and mental development, spastic-rigidity, and deaf-mutism. The disease just debilitated the entire community.”

DeLong remembers in particular one young woman whose limbs were so twisted that she had to use her elbows to drag her body across the floor of her family hut, with all the painful laboriousness of a beached mermaid. Her family members would often prop her up outside, then carry her in when it began to rain.

When this same young woman became pregnant, she might have given birth to a baby as impaired by iodine deficiency as she had been. But as part of the local IDD control project, she received an intramuscular injection of iodine-in-oil during the second trimester of her pregnancy. The daughter she delivered is now a college graduate who speaks three languages.

In the decades since his first encounters with IDD, DeLong, a professor of pediatric neurology at Duke University, has witnessed many other instances of the transformative power of even tiny doses of iodine in preventing the disorder. So when he encountered unusually high rates of the disease in Xinjiang, a province in northwestern China, he became determined to find a solution.


Symptoms of iodine deficiency have plagued humankind for millennia. A second-century frieze of Buddha and his disciples, for example, shows a figure with goiter. Drawings from the thirteenth century depict people with goiter and cretinism, and Renaissance painters from Dürer to Rubens captured on canvas many subjects with goitrous necks.

Today, iodine deficiency still condemns many thousands of children to cretinism, tens of millions to varying degrees of mental retardation, and hundreds of millions to milder degrees of mental and physical impairments. An estimated 1.6 billion people are at risk for IDD, now recognized as the most common preventable cause of mental retardation worldwide.

Nearly one-third of the globe’s inhabitants live in areas of natural iodine deficiency. The regions most affected are mountainous ones, where glaciation, snow, and rainfall leach the mineral from the soil; flood plains such as that of the Ganges; and inland continental expanses far from the world’s oceans, which are the primary sources of iodine.

Countries around the world have responded to the problem, adding iodine to tea in Tibet, bread in Australia, and fish paste in Thailand. Yet fortifying ordinary table salt with iodine, the most common method, is also considered the best. IDD was endemic in the Appalachian, Great Lakes, and mountainous western regions of the United States, for example, until the 1920s, when iodized salt consumption became widespread.

Iodized salt does not offer a solution for people living in many remote areas of the world, though. Some communities find it too expensive or difficult to obtain; others reject it as less flavorful than locally available salt. Efforts to provide oral or injected iodine-in-oil to people living in areas with endemic IDD often fail because of issues of cost, distribution, or sustainability. Cultural traditions and superstitions may create obstacles as well.


The problem of iodine deficiency is hardly new to Xinjiang: while traveling through the region during the thirteenth century, Marco Polo recorded observations of people with diminished intelligence, deafness, spasticity, and enlarged throats. Throughout the intervening centuries, the tragic consequences of iodine deficiency have continued to plague Xinjiang, whose water and soil contain some of the planet’s lowest levels of naturally occurring iodine.

A constellation of factors had contributed to the failure of efforts to provide the people of Xinjiang with iodine. Some of the barriers were cultural. Forty percent of the region’s inhabitants are Uighurs, a Turkic people who comprise the largest of China’s minority groups. The Uighurs—most of whom live in villages dotting the perimeter of the Taklimakan Desert—find iodized salt not only less affordable, but also less savory than the rock salt so abundant in the desert.

“The Uighurs have a tradition of picking rock salt off the desert floor, dissolving it in big clay pots, and then using the brine for cooking,” DeLong says. “The desert salt has a ‘brighter’ flavor—likely from its magnesium content—but unfortunately it contains little iodine.”

Exacerbating the problem was the centuries-long contentious relationship between the Uighurs and the majority Han, who dominate the country’s central government. And so the Chinese authorities’ attempt to offer iodine pills failed, among other reasons, because the Uighur women suspected officials of trying to slip them contraceptives.

Efforts to introduce iodine intramuscularly had fallen short as well. Injections such as those used in Ecuador required medical expertise and supplies not widely available in Xinjiang. And local public health authorities were skittish about injections for another reason: in 1988, the area had suffered a hepatitis epidemic that had left 500 dead, and they wanted to avoid the risks of shared needles.

When DeLong first visited Xinjiang in 1989, he found one in ten children suffering from severe IDD and one in three exhibiting symptoms of iodine deficiency. “We were examining literally hundreds of children,” he says. “Some showed extreme mental retardation and could not walk, stand, or even sit. Even the ones without severe signs were slack and dull-eyed. They simply lacked the natural vivacity of children.”

During repeated trips to Xinjiang, as DeLong pursued his initial goal of studying the impact of iodine deficiency on fetal brain development, he pondered ways to prevent the calamity from occurring in the first place. By then he had grown close to two Chinese colleagues, Ma Tai, a leading expert on IDD in China, and Cao Xue-yi, the head of Xinjiang’s Health and Anti-Epidemic Station. Together they explored—and rejected as impractical—possible solutions to the seemingly intractable problem.

Then, one day after working in the clinic, the collaborators happened to drive to the countryside to see the main irrigation dam, 20 miles upstream. “We looked out over the Hotien River with its complex system of irrigation canals, the basis of all human life there,” DeLong says. “It was fascinating, but I didn’t give it much thought. Back in the capital the next day, I chatted with a local water chemist about the concentrations of various minerals, such as iron and copper, in the water. But the penny still didn’t drop.”

That evening, DeLong says, “We were driving to a Uighur comedic performance when suddenly it hit me. I practically shouted, ‘We can drip potassium iodate into the irrigation water!’ Dr. Ma threw up his hands and cried, ‘We’ll all go to jail!’ But by the next day, he was thinking about it seriously. It quickly became clear that the idea could work.”

DeLong had realized that iodinating the irrigation water could protect entire villages. The plants would absorb the iodine that had leached from the treated water into the soil. The animals, in turn, would ingest the iodine-rich plants. At the top of the food chain, people would finally consume sufficient levels of iodine.

Obtaining approval for his proposal from suspicious local communities would be tricky, DeLong knew. But an incident that had taken place the previous year had helped convince the wider Uighur community of the physician’s good intentions.

Late one afternoon DeLong, Ma, and their team were working in a small clinic in the village of Tusala when a sandstorm swept in from the desert. DeLong’s wife, Nancy, who has shared his IDD work at every stage, recalls that day.

“About three o’clock the room suddenly became almost as dark as night, with an eerie yellow light,” she says. “A gale force wind was blowing the trees sideways and sending dust swirls skyward. The patients covered their mouths and noses with their headscarves and huddled along an inside corridor. The lights flickered and went out.”

Just as the medical team had begun examining patients again, a great commotion of people burst into the room; they were bringing in a young boy who had picked up a live cable blown down by the storm. For several long minutes DeLong desperately tried mouth-to-mouth resuscitation and chest compressions but could get no response. Then someone mentioned that the boy’s father had transported him to the clinic in a donkey cart for six kilometers.

“I shined a light into the boy’s eyes,” Nancy DeLong says. “He was dead. Bob straightened up, told the father he was sorry, and stood helplessly in tears, as the father, fighting for control, gently lifted his child, wrapped a sheet—now a shroud—around him, and carried him from the room, clasped tightly to his breast.”

“Tragically, our sustained efforts couldn’t revive the boy,” Ma later recounted. “Yet his family bent down to express their heartfelt gratefulness. And the story about the American doctor spread, even to the capital.”

The reservoir of good will that DeLong generated that day may have helped his cause when, a year later, he and his team explained the proposal to iodinate the irrigation water to villagers in the chosen site of Long Ru township. Each phrase was painstakingly translated into Mandarin, then into Uighur. To the team members’ relief, they found a receptive audience. The villagers discussed the dilemma, then took a vote.

“When we met with the village leaders in Long Ru, the temperature was hovering near zero,” remembers Nancy DeLong. “They were all sitting around in their thin coats and wool hats. Their breaths sent tiny clouds into the air and their wonderful weathered faces looked like stone. Then suddenly everyone erupted: ‘Yes, we approve!’ ”


One of the first tasks facing DeLong’s team was calculating the flow rate of the canal. Impatient for the arrival of outside help, DeLong drew on his youthful penchants. In the eighth grade he had taken an interest inventory test that recommended he become a county agricultural agent. So it was with a sense of familiarity that he tackled the challenge.

“We stripped to our undershorts, waded into the canal to measure its cross-section, then threw sticks in the water and recorded how fast they floated by,” DeLong says. “I felt like I was back on my uncle’s farm in Indiana, tossing twigs into the creek. Much later, we learned that our estimate was within 10 percent of the official measurement.”

The team next devised a primitive delivery system: a 55-gallon oil drum coated with epoxy paint to prevent oxidation and rigged with a spigot that could be turned on and off. The spigot was not precise enough in regulating the output, though, so they used intravenous tubing and two clamps to cobble together a simple valve to provide a steady flow. They tested their contraption overnight in a hotel parking lot—and found that it worked.

Next they perched the oil drum on a wooden bridge spanning the irrigation canal. For two weeks during the spring of 1992, the team dripped a 5 percent solution of potassium iodate into the canal, which supplied four villages in Long Ru township with water. They hired a local villager to protect the drum from theft, refill the tank, and monitor the flow rate. At night, the man would unfurl his rolled-up blanket and sleep right on the rough-hewn bridge.

Soon more men were needed to safeguard more barrels. Decisions about the placement of the drums and the timing of the dripping were made with the input of local officials, particularly the kuai-ji, or water accountants, who oversaw all aspects of irrigation for the region. During the spring planting, as many as 20 tankfuls of potassium iodate solution were dripped into a canal from a single site.


Measurements from samples sent to a laboratory in Ürümqi, the capital, revealed that iodine concentration in treated areas had increased four-fold in the soil within weeks and three-fold in the crops and animals within months. Within one year, nearly all local women of childbearing age had iodine levels well out of the danger zone. The results were most dramatic in children conceived after the program began. Within three years of the first dripping, the infant mortality rate fell by half. Later assessments showed that the average height of five-year-olds had increased by four inches. And the intelligence quotients of children born after the dripping averaged 16 points higher than those of children born before the dripping.

“When we first arrived in Xinjiang, I thought the children were withdrawn because they were afraid of us,” says Nancy DeLong. “But as time passed, and the treated water took effect, I realized that the children were growing livelier.”

Local livestock thrived too. Within a year, sheep production had increased by 40 percent. And as a result, the average annual family income rose 5 percent.

From their initial study, published in 1994, DeLong and his colleagues concluded that treating irrigation water was an effective and relatively inexpensive method of supplying iodine to people in irrigated areas where IDD is endemic. With the support of the Thrasher Foundation, the Joseph P. Kennedy, Jr. Foundation, Kiwanis International, and UNICEF, the team undertook a major expansion of its program in 1997. Iodine dripping now protects 2.6 million people from IDD in the 16 most severely deficient areas of Xinjiang. Thirteen and one-half tons of potassium iodate have already been dripped, at a cost of less than six cents per person.

Iodine concentrations in soil, crops, meat, and human urine, monitored since the one-time dripping, indicate that a single dripping can provide iodine for at least six years. Iodination of irrigation water has now been undertaken in Inner Mongolia and is planned for Kyrgyzstan.


But what about iodine-deficient areas of the world where widespread irrigation doesn’t exist? In the heart of Siberia, at the geographic center of Asia, lies Tuva, the poorest republic in Russia. Home to a Mongolian people, Tuva is renowned for its rich folklore, skilled artisans, andkhoomei, a form of throat singing whose haunting notes are said to mimic the wind sweeping across the steppes. The area is also known for its elevated rates of IDD.

There infant mortality runs high, and in some areas nearly half of the newborns have hypothyroidism caused by iodine deficiency. The lasting economic disruption that followed the collapse of the Soviet Union has made iodized salt an impractical solution. And, unlike the people of Xinjiang, the Tuvans do not rely on irrigation water. They depend instead on animal herding for their livelihood, raising sheep, cattle, horses, goats, and even camels on the elevated steppes of their ancestral homeland.

When DeLong reflected on the high rates of severe IDD in Tuva, he reasoned that the most efficient way to distribute iodine would be by adding potassium iodate to salt licks for the animals on whose products—mutton, beef, milk, cheese, and yogurt—the people relied. “We knew,” he says, “that iodinating salt licks had been successful in the Netherlands and England, where the iodine levels in cows rose dramatically.”

The plan required machinery for crushing rock salt, adding iodate, and making salt blocks. The Tuvan government approved the plan and promised to supply the potassium iodate and workers to operate the plant. Local authorities agreed to distribute free iodinated salt blocks to all herders in the region.

But the machinery still needed to be financed, manufactured in India, and transported by ship, the Trans-Siberian railway, and truck to Tuva. And all this had to be arranged from half a world away. DeLong secured financial support from friends and members of Kiwanis International. By the fall of 2002 the machinery had arrived. So DeLong returned to Tuva with his Kiwanian friends.

“One of them was a high school mechanical shop teacher,” DeLong says, “and he had that machine up and running in two days.” By the time the Kiwanians staged a repeat visit the following spring, local workers were turning out iodinated salt blocks and distributing them to Tuva’s mountain communities.

“Their sheep had been producing poor quality wool because of the lack of iodine,” DeLong says. “If we’re lucky, the salt licks should improve not only human health, but also the health of the local wool industry.”

DeLong and his team hope that, as knowledge of the health benefits, affordability, safety, and economic advantages of iodinating irrigation water and salt licks spreads to affected areas of the world, so will the adoption of their practical methods. “With all the medical technologies we have to work with today,” DeLong says, “it’s easy to forget the incredible difference an ancient trace mineral can make to a single life, to a community—even to the world.”

Gordon Worley ’73 is an associate clinical professor at the Duke University School of Medicine.

This article appeared in the Spring 2004 issue of the Harvard Medical Alumni Bulletin.

Photo caption: Gordon Worley’s idea to introduce an iodine solution into the water systems of a remote part of China helped reduce the incidence of iodine deficiency disorders among residents.

Sunday 15 January 2012

Iodine is Critical - Feed your thyroid: Nutrients and foods that nourish the thyroid

Feed your thyroid: Nutrients and foods that nourish the thyroid

Want to ensure good thyroid function through what you eat? The following foods contain nutrients helpful for thyroid function.

Thu, Jan 12 2012 at 1:15 AM EST
picture of seaweedPhoto: Jeff Kubina/Flickr
Are you sluggish, stiff, have unexplained weight gain, and cold all the time? You may have an under-active thyroid. According to the Mayo clinic, these are some of the many signs that your thyroid is sluggish.
If you suspect you have thyroid issues, you should, of course, seek professional help. But what if you want to stave off future problems? Are there any foods or supplements that you can take to help give your body what it needs to have a healthy metabolic function?
Some experts say yes. According to John Dommisse, MD,certain minerals and vitamins play a supportive role in thyroid function. Iodine, selenium, zinc, magnesium and Vitamin A are all important nutrients the body uses to manufacture thyroid hormones. This means if you have serious thyroid issues, it could be helpful to have blood tests drawn to see what your nutritional status is. For the rest of us, eating specific, nourishing foods may help give our bodies the nutrition they need to have well-performing thyroids.
Let’s start with vitally important iodine. Iodine isn’t found in high amounts in many foods (which is why, if you are low, you may need to supplement with your health provider's supervision). Yet there is one food that is an excellent source if eaten on a regular basis: seaweed (check out this fact sheet for amounts of iodine in food).
However, unlike our Japanese friends, most Americans aren’t used to eating it on a regular basis. My family developed a taste for seaweed by enjoying sushi (we don’t eat a lot of raw fish, so we especially enjoy avocado sushi). We also like eating seaweed chips that are lightly fried in decent oil and salted or slightly sweetened (bought at the health food store). We buy dulse flakes and sprinkle it over rice, and you can also buy kelp salt replacers (add to soups and other dishes for a “salty taste”). Drop kumbu in homemade simmering broths, or in a pot of homemade beans during the beginning stages. It adds not only iodine, but other important minerals. It also seems to help make beans more digestible and less gas-causing.
For selenium, brazil nuts are one of the best sources. Eating 3-5 a days provides plenty. Other sources include crimini mushrooms, cod and mustard seeds. For a selenium feast, why not make a braised cod dish with a mustard sauce and Garlicky Sauteed Mushrooms on the side?
For zinc, eating calf’s liver, venison and beef top the list. Eating that steak may not be so bad for you after all (though I highly recommend you buy grass-fed beef). Lamb, spelt, scallops and sesame seeds or pumpkin seeds are also good sources. One zinc-rich favorite snack around here is pumpkin seeds with raisins. Pumpkin seeds are also one of the best sources for another important, thyroid-building nutrient, magnesium. Other food sources of magnesium include spinach, Swiss chard, sesame seeds and cashews.
Finally, for Vitamin A, I feel one of the very best natural sources is fermented cod liver oil. Read more about this super food here. Plant based food sources include sweet potatoes and carrots.
However, it’s not just important to build up your nutrient intake — it’s also important to avoid or limit certain foods that actually have a goitrogen effect (that is, they suppress the thyroid). Soy is the biggest offender. Even cruciferous vegetables, when eaten often raw, can be an issue.
While a serious thyroid issue needs professional help, we all need these nutrients for good health. Adding in foods rich in the above nutrients can help make us well-nourished and give our body needed nutrients for making thyroid hormones.
I’d love to hear your thoughts! Do you have any recipes to share that would provide a nutrient rich, thyroid supporting meal?

Iodine Deficiency Strikes Again- The Times of India reports-After milk, salt under quality check scanner - 71 Million Affected 200 Million at Risk

NEW DELHI: After milk, salt - another most common food item - is under the Food Safety Standards Authority of India's (FSSAI) scanner.

The FSSAI is collecting salt samples from across metros to check iodine levels. The study aims to find out how much iodine is available in the salt being sold to consumers.

"We want to see how much iodine is being consumed through salt by consumers. The study is being carried out in metros like Delhi, Mumbai, Chennai, Kolkata, Pune, Bangalaore and Guwahati among others. Around 100 samples of salt- both packed and being sold loose - are being tested from each city. The results will be available soon," a health ministry official told TOI.

According to the Coverage Evaluation Survey, adequately iodated salt consumption in the country was about 71% and the rest (29%) contained nil and inadequate iodine. About 71 million Indians are suffering from Iodine Deficiency Disorders (IDD). IDD is the leading cause of mental retardation globally. Every year, 13 million Indian children are born unprotected from brain damage caused by iodine deficiency.

It is estimated that 200 million Indians are exposed to the risk of IDD.

Health ministry data says that out of 324 districts in all the 28 states, 263 districts are endemic, where the prevalence of IDD is more than 10%.

Under the 12th Five Year plan, India aims to bring down prevalence of IDD below 5%. By 2017, the Union health ministry wants to ensure 100% consumption of adequately iodated salt in households.

"We want to conduct a fresh IDD survey/resurvey of 643 districts of the country. It is estimated that an amount of Rs 643 lakh will be required during the entire Plan period for the survey. During the 12th Plan, we have asked the Planning Commission for Rs 1,225 lakh to set up one IDD monitoring lab with one laboratory technician and one lab assistant for every state," a ministry official said.

Sunday 8 January 2012

World's Healthiest Foods Highlights American's Risk of Iodine Deficiency- Essential Nutrient and Key to BioLargo Technology

The World's Healthiest Foods

Americans at High Risk for Iodine Deficiency: Sea Vegetables a Reliable Source

Research published in Environmental Science and Technology, (Dasgupta P, Liu Y, et al.) has revealed that iodized salt is not likely to contain the amount of iodine it's supposed to, and even if it did, many Americans are cutting back on salting home-cooked meals.

Because excessive sodium intake can increase hypertension risks, many agencies now recommend reducing salt intake. A 1995 report found 58% of men and 68% of women reported never using salt, using "lite" salt, or rarely using ordinary table salt.

In addition, the use of iodized salt is not mandatory in the U.S., and virtually all of the salt used in restaurants and processed foods in the U.S. is not iodized, leaving Americans at high risk for iodine deficiency.

Although product labels state that U.S. iodized salt contains 45 µg of iodine per gram, when University of Texas researchers analyzed 88 samples of iodized table salt from 40 states, 53% of samples contained less. Iodine values in freshly opened, top-of-the can samples ranged from as little as 12.7 to 129 μg/kg. And the amount of iodine within each can was not homogenous but varied as much as 3.3 times among the 5 samples taken at different depths from the same container. In addition, iodine was also found to decrease greatly during high humidity storage, although light or heat had little effect.

In sum, even if you don't eat out a lot and are using iodized salt, you have no idea how much iodine it is actually providing, and the longer you've had that container of salt, the more likely its iodine content has decreased.

Why should we be concerned? Iodine is necessary for the body's production of thyroid hormones, which, in addition to regulating metabolic rate, direct brain development, making iodine critical starting in the first trimester of pregnancy through adolescence.

Lack of sufficient iodine is the leading cause of preventable mental retardation in the world. Even a mild iodine deficit in pregnant women, infants, and children, can lower intelligence by 10-15 IQ points, lessening an individual's mental abilities throughout life.

Public-health studies over the past 30 years indicate that iodine levels in the U.S. population, particularly in women of childbearing age, are too low. Urinary iodine (the standard means of evaluating iodine levels in the body) has plummeted by almost 50% in adults, and the frequency of moderate iodine deficiency (urinary iodine excretion of less the 50 μg per liter) in pregnant women has jumped from 1% to 7%.

In an editorial in the New England Journal of Medicine entitled "Iodine Nutrition - More is Better," thyroidologist Robert Utiger of Harvard Medical School urges that the recommended daily intake of iodine be increased to 300 to 400 μg.

Practical Tip: Kelp, dulse, hijiki, and nori, can be relied upon as an excellent source of iodine (a mere ¼ cup supplies 415μg). To ensure you are getting enough iodine, make sea vegetables a staple in your healthy way of eating.

One important caveat: Purchase only certified organic sea vegetables to ensure they are free of contamination. Sea vegetables have a high affinity for heavy metals, and if grown in polluted waters, can soak up not only healthful minerals, but also contaminants such as arsenic, lead, cadmium or mercury. (van Netten C, Hoption Cann SA, et al. Sci Total Environ)

Dasgupta P, Liu Y, Dyke J. Iodine nutrition: iodine content of iodized salt in the United States. Environ. Sci. Technol., 42 (4), 1315-1323, 2008.

Utiger RD, N Engl J Med. 2006 Jun 29;354(26):2819-21, PMID: 16807421

van Netten C, Hoption Cann SA, Morley DR, van Netten JP. Elemental and radioactive analysis of commercially available seaweed. Sci Total Environ. 2000 Jun 8;255(1-3):169-75. PMID: 10898404

Iodine- Part of the World's Healthiest Foods - Essential Nutrient - And Key Feature of BioLargo Technology

The World's Healthiest Foods


(Link Here)

What can high-iodine foods do for you?

  • Help ensure proper thyroid gland functioning

What events can indicate a need for more high-iodine foods?

  • Goiter (enlargement of the thyroid gland)
  • Fatigue
  • Weakness
  • Depression
  • Weight gain

Concentrated food sources of iodine include sea vegetables, yogurt, cow's milk, eggs, strawberries and mozzarella cheese. Fish and shellfish can also be concentrated sources of iodine.

Nutrient Chart


What is Iodine?

If you backpack in the mountains, you may have used iodine tablets to purify your drinking water. Or, perhaps you've used an iodine-based disinfectant to clean a minor skin wound. But did you know that iodine is essential to life?

Iodine, a trace mineral, is required by the body for the synthesis of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). (T4 contains 4 iodine atoms. When one of the iodine atoms is stripped off of T4, it becomes T3, with 3 iodine atoms remaining.)

Under normal circumstances, your body contains approximately 20 to 30 mg of iodine, most of which is stored in your thyroid gland, located in the front of your neck, just under your voice box. Smaller amounts of iodine are also found in lactating mammary glands, the stomach lining, salivary glands, and in the blood.

How it Functions

What is the function of iodine?

As a component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), iodine is essential to human life. Without sufficient iodine, your body is unable to synthesize these hormones, and because the thyroid hormones regulate metabolism in every cell of the body and play a role in virtually all physiological functions, an iodine deficiency can have a devastating impact on your health and well-being.

Regulating thyroid hormones

The synthesis of thyroid hormones is tightly controlled. When the amount of thyroid hormone in your blood drops, the pituitary gland secretes a hormone called thyroid-stimulating hormone (TSH). As its name suggests, TSH then stimulates the thyroid gland to increase its uptake of iodine from the blood, so that more thyroxine (T4) can be synthesized. When necessary, thyroxine is then converted to the metabolically active triiodothyronine (T3), a process that involves removing one iodine atom from T4.

Several other physiological functions for iodine have been suggested. Iodine may help inactivate bacteria, hence its use as a skin disinfectant and in water purification. Iodine may also play a role in the prevention of fibrocystic breast disease, a condition characterized by painful swelling in the breasts, by modulating the effect of the hormone estrogen on breast tissue. Finally, researchers hypothesize that iodine deficiency impairs the function of the immune system and that adequate iodine is necessary to prevent miscarriages.

Deficiency Symptoms

What are deficiency symptoms for iodine?

In the early part of the 20th century, iodine deficiency was quite common in the United States and Canada. However, this problem has since been almost completely resolved by the use of iodized salt. In addition, iodine is now added to animal feed, which has increased the iodine content of commonly consumed foods, including cow's milk.

Unfortunately, in countries where iodized salt is not commonly consumed, iodine deficiency remains a signficant problem. Dietary deficiency of this vital mineral results in decreased synthesis of thyroid hormone.

Goiter, or enlargement of the thyroid gland, is usually the earliest visible symptom of iodine deficiency. (Goiter can occur for many other reasons as well, but iodine deficiency is among the most common causes worldwide.) The enlargement of the thyroid results from overstimulation of the thyroid gland by thyroid stimulating hormone (TSH), as the body attempts to produce increased amounts of thyroid hormone.

Goiter is more common in certain geographical areas of the world where iodine is lacking in the diet and where selenium is lacking in the soil. (Selenium is directly involved with certain activities of the thyroid gland.)

Iodine deficiency may eventually lead to hypothyroidism, which causes a variety of symptoms including fatigue, weight gain, weakness and/or depression. Interestingly, iodine deficiency can also cause hyperthyroidism, a condition characterized by weight loss, rapid heart beat, and appetite fluctations.

Severe iodine deficiency during pregnancy or infancy causes cretinism, a condition characterized by hypothyroidism leading to failure of the thyroid gland and/or severe mental retardation, stunted physical growth, deafness, and spasticity. If discovered in its initial stages, cretinism can be corrected with iodine supplementation.

Toxicity Symptoms

What are toxicity symptoms for iodine?

Accidental overdose of iodine from medications or supplements in amounts exceeding one gram may cause burning in the mouth, throat and stomach and/or abdominal pain, nausea, vomiting, dirarrhea, weak pulse, and coma.

It is difficult to take in too much iodine from food sources alone. It is estimated that men and women consume at most 300 mcg and 210 mcg of iodine per day, respectively. In general, even high intakes of iodine from food are well-tolerated by most people.

However, in certain circumstances, excessive consumption of iodine can actually inhibit the synthesis of thyroid hormones, thereby leading to the development of goiter (enlargement of the thyroid gland) and hypothyroidism. Excessive iodine intake may also cause hyperthyroidism, thyroid papillary cancer, and/or iodermia (a serious skin reaction).

In an attempt to prevent these symptoms of iodine toxicity, the Institute of Medicine established the following Tolerable Upper Intake Levels (TUL) for iodine:

  • 1-3 years: 900 mcg
  • 4-8 years: 300 mcg
  • 9-13 years: 600 mcg
  • 14-18 years: 900 mcg
  • 19 years and older: 1,100 mcg
  • Pregnant women 14-18 years: 900 mcg
  • Pregnant women 19 years and older: 1,100 mcg
  • Lactating women 14-18 years: 900 mcg
  • Lactating women 19 years and older: 1,100 mcg

It is important to note that if you have an autoimmune thyroid disease (for example, Grave's disease or Hashimoto's disease) or if you have experienced an iodine deficiency at some point in your life, you may be more susceptible to the dangers of excessive iodine consumption, and may, therefore, need to monitor your intake of iodine more carefully.

Impact of Cooking, Storage and Processing

How do cooking, storage, or processing affect iodine?

Food processing practices often increase the amount of iodine in foods. For example, the addition of potassium iodide to table salt to produce "iodized" salt has dramatically increased the iodine intake of people in developed countries. In addition, iodine-based dough conditioners are commonly used in commercial bread-making, which increases the iodine content of the bread.

Factors that Affect Function

What factors might contribute to a deficiency of iodine?

Since absorption of iodine from the digestive tract is very thorough, deficiency of iodine typically occurs from too little intake of iodine-containing foods. However, there has been some controversy surrounding the impact of diet not on iodine absorption, but on iodine utilization by the thyroid gland. Since the thyroid requires iodine to make thyroid hormones, this utilization is essential. Two groups of substances found in food - isoflavones, most commonly found in soy foods, and thiocyanates, most commonly produced in the body from glucosinolates found in cruciferous vegetables like broccoli - have been shown to interfere with iodine utilization by the thyroid gland, but only under very specific circumstances. These circumstances involve simultaneous dietary deficiency of iodine or selenium (or both) and imbalanced overall dietary intake. We're not aware of any evidence showing problems with iodine metabolism by the thyroid gland when either soy foods or cruciferous vegetables are eaten in moderate amounts in an overall balanced diet that also contains appropriate amounts of iodine and selenium. Since soy foods and cruciferous vegetables provide so many well-documented health benefits, we do not believe there is ordinarily any reason to eliminate these foods from the diet for iodine-related reasons. However, for individuals with a history of thyroid problems, poor dietary balance and deficient intake of iodine and/or selenium, we recommend consultation with a healthcare provider to decide about the role of these foods in health support.

Drug-Nutrient Interactions

What medications affect iodine?

Amiodarone, a drug most commonly sold under the brand name Cordarone (TM), is sometimes used to treat irregular heart beat. This medication contains iodine and can disrupt proper thyroid function.

Similarly, erythrosine, a red coloring agent commonly used in foods and medications, also contains significant amounts of iodine and may also impact thyroid activity.

Nutrient Interactions

How do other nutrients interact with iodine?

The conversion of thyroxine (T4) to triiodthyronine (T3) requires the removal of an iodine molecule from T4. This reaction requires the mineral selenium. The iodine molecule that is removed gets returned to the body's pool of iodine and can be reused to make additional thyroid hormones.

If your body is deficient in selenium, the conversion of T4 to T3 is slowed, and less iodine is available for the thryoid to use in making new hormones.

Animal studies have shown that arsenic interferes with the uptake of iodine by the thyroid, leading to goiter. In addition, dietary deficiency of vitamin A,vitamin E, zinc and/or iron can exaggerate the effects of iodine deficiency.

Health Conditions

What health conditions require special emphasis on iodine?

Iodine may play a role in the prevention and/or treatment of the following health conditions:

  • Cognitive impairment
  • Cretinism
  • Fibrocystic breast disease
  • Goiter
  • Hyperthyroidism
  • Hypothyroidism
  • Multiple miscarriages

Form in Dietary Supplements

What forms of iodine are found in dietary supplements?

The elemental form of iodine is available in dietary supplements as iodine caseinate and in products that contain kelp. Many supplements contain iodine complexed with potassium or sodium, called potassium iodide or sodium iodide, respectively.

Food Sources

Introduction to Nutrient Rating System Chart

The following chart shows the World's Healthiest Foods that are either excellent, very good or good sources of this nutrient. Next to each food name you will find the following information: the serving size of the food; the number of calories in one serving; DV% (percent daily value) of the nutrient contained in one serving (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. Read detailed information on ourNutrient Rating System.

Introduction to Nutrient Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the World's Healthiest Foods that are either an excellent, very good, or good source of iodine. Next to each food name, you'll find the serving size we used to calculate the food's nutrient composition, the calories contained in the serving, the amount of iodine contained in one serving size of the food, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

World's Healthiest Foods ranked as quality sources of:
Foods Rating
Sea Vegetables0.25 cup8.6415.00276.7579.1excellent
Yogurt245 g154.387.2258.16.8very good
Milk1 cup122.058.5639.05.8very good
Eggs1 each77.527.0018.04.2very good
Strawberries1 cup46.112.968.63.4very good
Cheese1 oz-wt72.
World's Healthiest
Foods Rating
very goodDV>=50%ORDensity>=3.4ANDDV>=5%

Public Health Recommendations

What are current public health recommendations for iodine?

In 2000, the Institute of Medicine at the National Academy of Sciences developed new Dietary Reference Intakes for iodine. Adequate Intakes were established for children up to one year old, and Recommended Dietary Allowances were determined for all people over one year old. These recommendations appear below:

  • 0-6 months: 110 mcg
  • 7-12 months: 130 mcg
  • 1-8 years: 90 mcg
  • Boys 9-13 years: 120 mcg
  • Girls 9-13 years: 120 mcg
  • Boys 14-18 years: 150 mcg
  • Girls 14-18 years: 150 mcg
  • Men 19 years and older: 150 mcg
  • Women 19 years and older: 150 mcg
  • Pregnant women 14 years and older: 220 mcg
  • Lactating women 14 years and older: 290 mcg

In an attempt to prevent these symptoms of iodine toxicity, the Institute of Medicine established the following Tolerable Upper Intake Levels (UL) for iodine:

  • 1-3 years: 900 mcg
  • 4-8 years: 300 mcg
  • 9-13 years: 600 mcg
  • 14-18 years: 900 mcg
  • 19 years and older: 1,100 mcg
  • Pregnant women 14-18 years: 900 mcg
  • Pregnant women 19 years and older: 1,100 mcg
  • Lactating women 14-18 years: 900 mcg
  • Lactating women 19 years and older: 1,100 mcg

For more details on this, see the Toxicity Symptoms section above.


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