Iodine is an important nutrient that helps our bodies maintain normal levels of thyroid hormones. In this article, we discuss which vegetables are highest in iodine, as well as which have other beneficial nutrients for thyroid health. Vegetables like spinach, kale, turnip greens and radishes can be a great source of iodine.
What foods Have Iodine?
Iodine insufficiency is one of the main causes of preventable mental deficiency and negatively affects the person during their whole life, starting from their mother’s womb. Iodine is an important component that produces thyroid hormones that are needed for the development of the brain and nervous system and the maintenance of the body temperature and energy.
To prevent health problems due to iodine deficiency, normal table salts have been converted to salt with iodine. However, excess salt consumption can cause other health problems thus we can add other foods to our diet that include iodine.
The daily advised iodine intake for an adult is 150 mcg.
SEA FOODS: Fish (especially salt water fish) are rich in iodine and can be consumed as a source of iodine.
Tuna, haddock, cold water and deep water fish have a high amount of iodine. Shrimps and other shelled sea food can be used to prevent iodine insufficiency.
SALT WITH IODINE: To replace your daily table salt with iodine salt will cover your daily iodine requirement.
VEGETABLES: Spinach, soya beans, turnip, beet, courgette, baked beans and garlic are vegetables rich in iodine. These vegetables can also be consumed as a source of vitamin and antioxidants.
STRAWBERRY: Fruit are not usually a good source of iodine and only a few fruits contain iodine. Strawberries that are amongst the few fruits containing iodine can be added to the list of healthy foods due to its low calories and minerals. 6-7 strawberries a day cover 8% of the daily iodine intake.
YOGHURT MILK AND CHEESE: Milk and dairy products are rich in iodine. One bowl of yoghurt covers 60%; one cup of milk covers 40%, one egg covers 20% of the daily iodine intake.
Iodine
What is iodine and what does it do?
Iodine is a mineral found in some foods. The body needs iodine to make thyroid hormones. These hormones control the body’s metabolism and many other important functions. The body also needs thyroid hormones for proper bone and brain development during pregnancy and infancy. Getting enough iodine is important for everyone, especially infants and women who are pregnant.
How much iodine do I need?
The amount of iodine you need each day depends on your age. Average daily recommended amounts are listed below in micrograms (mcg).
| Life Stage | Recommended Amount |
|---|---|
| Birth to 6 months | 110 mcg |
| Infants 7–12 months | 130 mcg |
| Children 1–8 years | 90 mcg |
| Children 9–13 years | 120 mcg |
| Teens 14–18 years | 150 mcg |
| Adults | 150 mcg |
| Pregnant teens and women | 220 mcg |
| Breastfeeding teens and women | 290 mcg |
What foods provide iodine?
Iodine is found naturally in some foods and is also added to salt that is labeled as “iodized”. You can get recommended amounts of iodine by eating a variety of foods, including the following:
- Fish (such as cod and tuna), seaweed, shrimp, and other seafood, which are generally rich in iodine
- Dairy products (such as milk, yogurt, and cheese) and eggs, which are also good sources of iodine
- Iodized salt, which is readily available in the United States and many other countries*
*Processed foods, such as canned soups, almost never contain iodized salt. In addition, specialty salts, such as sea salt, kosher salt, Himalayan salt, and fleur de sel, are not usually iodized. Product labels will indicate if the salt is “iodized” or provides iodide.
What kinds of iodine dietary supplements are available?
Iodine is available in dietary supplements, usually in the form of potassium iodide or sodium iodide. Many multivitamin-mineral supplements contain iodine. Dietary supplements of iodine-containing kelp (a seaweed) are also available.
Am I getting enough iodine?
Most people in the United States get enough iodine from foods and beverages. However, certain groups of people are more likely than others to have trouble getting enough iodine:
- People who do not use iodized salt. Adding iodine to salt is the most widely used strategy to control iodine deficiency. Currently, about 88% of households worldwide use iodized salt.
- Pregnant women. Women who are pregnant need about 50% more iodine than other women to provide enough iodine for their baby. Surveys show that many pregnant women in the United States may not get quite enough iodine, although experts do not know whether this affects their babies.
- People who follow a vegan diet or who eat few or no dairy products, seafood, and eggs. Seafood, eggs, milk, and milk products are among the best sources of iodine. People who don’t eat much of these foods or don’t eat them at all might not get enough iodine.
- People living in regions with iodine-deficient soils who eat mostly local foods. These soils produce crops that have low iodine levels. Among the regions with the most iodine-poor soil are mountainous areas, such as the Himalayas, the Alps, and the Andes regions, as well as river valleys in South and Southeast Asia.
- People who get marginal amounts of iodine and who also eat foods containing goitrogens. Goitrogens are substances that interfere with the way the body uses iodine. They are present in some plant foods including soy, and cruciferous vegetables such as cabbage, broccoli, cauliflower and brussels sprouts. For most people in the United States who get adequate amounts of iodine, eating reasonable amounts of foods containing goitrogens is not a concern.
What happens if I don’t get enough iodine?
Iodine deficiency is uncommon in the United States and Canada. People who don’t get enough iodine cannot make sufficient amounts of thyroid hormone. This can cause many problems. In pregnant women, severe iodine deficiency can permanently harm the fetus by causing stunted growth, intellectual disability, and delayed sexual development. Less severe iodine deficiency can cause lower-than-average IQ in infants and children and decrease adults’ ability to work and think clearly. Goiter, an enlarged thyroid gland, is often the first visible sign of iodine deficiency.
What are some effects of iodine on health?
Scientists are studying iodine to understand how it affects health. Here are some examples of what this research has shown.
Fetal and infant development
Women who are pregnant or breastfeeding need to get enough iodine for their babies to grow and develop properly. Breastfed infants get iodine from breast milk. However, the iodine content of breast milk depends on how much iodine the mother gets.
To make adequate amounts of iodine available for proper fetal and infant development, several national and international groups recommend that pregnant and breastfeeding women and infants take iodine supplements. The American Thyroid Association recommends that women who are pregnant, planning to become pregnant, or breastfeeding take a daily supplement containing 150 mcg iodine as potassium iodide. The American Academy of Pediatrics has similar guidance. However, only about half the prenatal multivitamins sold in the United States contain iodine.
Cognitive function during childhood
Severe iodine deficiency during childhood has harmful effects on the development of the brain and nervous system. The effects of mild iodine deficiency during childhood are more difficult to measure, but mild iodine deficiency might cause subtle problems with neurological development.
Giving iodine supplements to children with mild iodine deficiency improves their reasoning abilities and overall cognitive function. In children living in iodine-deficient areas, iodine supplements seem to improve both physical and mental development. More study is needed to fully understand the effects of mild iodine deficiency and of iodine supplements on cognitive function.
Fibrocystic breast disease
Although not harmful, fibrocystic breast disease causes lumpy, painful breasts. It mainly affects women of reproductive age but can also occur during menopause. Very high doses of iodine supplements might reduce the pain and other symptoms of fibrocystic breast disease, but more study is necessary to confirm this. Check with your healthcare provider before taking iodine for this condition, especially because iodine can be unsafe at high doses.
Radiation-induced thyroid cancer
Nuclear accidents can release radioactive iodine into the environment, increasing the risk of thyroid cancer in people who are exposed to the radioactive iodine, especially children. People with iodine deficiency who are exposed to radioactive iodine are especially at risk of developing thyroid cancer. The U.S. Food and Drug Administration has approved potassium iodide as a thyroid-blocking agent to reduce the risk of thyroid cancer in radiation emergencies.
Can iodine be harmful?
Yes, if you get too much. Getting high levels of iodine can cause some of the same symptoms as iodine deficiency, including goiter (an enlarged thyroid gland). High iodine intakes can also cause thyroid gland inflammation and thyroid cancer. Getting a very large dose of iodine (several grams, for example) can cause burning of the mouth, throat, and stomach; fever; stomach pain; nausea; vomiting; diarrhea; weak pulse; and coma.
The daily upper limits for iodine include intakes from all sources—food, beverages, and supplements—and are listed below. These levels do not apply to people who are taking iodine for medical reasons under the care of a doctor.
| Life Stage | Upper Limit |
|---|---|
| Birth to 12 months: | Not established |
| Children 1–3 years: | 200 mcg |
| Children 4–8 years: | 300 mcg |
| Children 9–13 years: | 600 mcg |
| Teens 14–18 years: | 900 mcg |
| Adults: | 1,100 mcg |
Does iodine interact with medications or other dietary supplements?
Yes. Iodine supplements can interact or interfere with medicines that you take. Here are several examples:
- Iodine supplements might interact with anti-thyroid medications such as methimazole (Tapazole®), used to treat hyperthyroidism. Taking high doses of iodine with anti-thyroid medications could cause your body to produce too little thyroid hormone.
- Taking potassium iodide with medicines for high blood pressure known as ACE inhibitors could raise the amount of potassium in your blood to an unsafe level. ACE inhibitors include benazepril (Lotensin®), lisinopril (Prinivil® and Zestril®), and fosinopril (Monopril®).
- The amount of potassium in your blood can also get too high if you take potassium iodide with potassium-sparing diuretics, such as spironolactone (Aldactone®) and amiloride (Midamor®).
Tell your doctor, pharmacist, and other healthcare providers about any dietary supplements and prescription or over-the-counter medicines you take. They can tell you if these dietary supplements might interact with your medicines. They can also explain whether the medicines you take might interfere with how your body absorbs or uses iodine or other nutrients.
Iodine and healthful eating
People should get most of their nutrients from food and beverages, according to the federal government’s Dietary Guidelines for Americans. Foods contain vitamins, minerals, dietary fiber, and other components that benefit health. In some cases, fortified foods and dietary supplements are useful when it is not possible to meet needs for one or more nutrients (for example, during specific life stages such as pregnancy). For more information about building a healthy dietary pattern, see the Dietary Guidelines for Americans and the U.S. Department of Agriculture’s MyPlate.
Are You Eating Enough Iodine-Rich Foods?
Iodine is considered one of the body’s vital nutrients, responsible for regulating thyroid function, supporting a healthy metabolism, aiding in growth and development, and preventing certain chronic diseases. Unfortunately, many adults don’t consume enough iodine-rich foods and, thus, suffer from an iodine deficiency.
Therefore, many suffer a range of negative health consequences as a result, known as iodine deficiency disorders.
Iodine is present throughout the body in just about every organ and tissue, needed by almost every bodily system to keep us alive and energized. For this reason, iodine deficiency poses many risks — an alarming thought considering that some sources suggest around 50 percent or more of the adult population in Western developed nations are at least somewhat iodine-deficient.
That’s why eating iodine-rich foods is so vital.
What Is Iodine?
Iodine is an essential mineral that enters the body through iodine-rich foods, including certain salts (“iodized salt”), eggs, sea vegetables, fish, beans and other foods. It’s found naturally in mineral-rich soils and also ocean water.
Iodine present in foods and iodized salt contains several chemical forms of iodine, including sodium and potassium salts, inorganic iodine (I2), iodate, and iodide. Iodine usually occurs as a salt and is called iodide when it does (not iodine).
We rely on iodine to create thyroxine (T4 hormone) and triiodothyronine (T3), two of the main hormones produced by the thyroid that control numerous important functions.
Iodide is absorbed in the stomach and enters the bloodstream, circulating to the thyroid gland, where it uses appropriate amounts for thyroid hormone synthesis. The unused iodine that we get from iodine-rich foods is then excreted in the urine.
A healthy adult usually has about 15–20 milligrams of iodine present within her body at one time — 70 percent to 80 percent of which is stored in the thyroid.
What is one of the most widespread symptoms of iodine deficiency? Thyroid disorders.
Thyroid function relies on proper levels of iodine, so too much (or too little) can cause many serious health problems.
Wondering, “How can I increase my iodine levels?” The very best way to maintain a normal iodine status is by eating foods high in iodine.
Top 15 Iodine-Rich Foods
What foods are high in iodine? Here are the best foods with iodine, according to the U.S. Department of Agriculture, with percentages below based on the recommended dietary allowance for the average adult:
- Dried kelp — 1 whole sheet dried: 19 to 2,984 micrograms (amounts vary widely — anywhere from 11 percent to 1,989 percent)
- Iodized salt — 1.5 grams/approx. ¼ teaspoon (71 percent DV)
- Cod (wild-caught) — 3 ounces: 99 micrograms (66 percent DV)
- Yogurt (organic, grass-fed and ideally raw) — 1 cup: 75 micrograms (50 percent DV)
- Dried wakame — 66 micrograms per gram (44 percent DV)
- Grass-fed milk — 1 cup: 56 micrograms (37 percent DV)
- Dried nori — 16–43 micrograms per gram (up to 29 percent DV)
- Eggs — 1 large: 24 micrograms (16 percent DV)
- Tuna — 1 can in oil/3 ounces: 17 micrograms (11 percent DV)
- Lima beans — 1 cup cooked: 16 micrograms (10 percent DV)
- Corn (organic) — 1/2 cup: 14 micrograms (9 percent DV)
- Prunes — 5 prunes: 13 micrograms (9 percent DV)
- Cheese (look for raw, unpasteurized) — 1 ounce: 12 micrograms (8 percent DV)
- Green peas — 1 cup cooked: 6 micrograms (4 percent DV)
- Bananas — 1 medium: 3 micrograms (2 percent DV)
The ocean is considered the prime provider of iodine‐rich foods, such as seaweeds, including kelp, hiziki, kombu, nori, arame and wakame. Kelp seaweed contains the highest amount of iodine among all foods.
Other good sources include cheddar and mozzarella cheeses, along with grass-fed butter (almost all dairy products contain some iodine), sardines, scallops, shrimp and other types of seaweeds.
What vegetables are high in iodine? As you can see above, some of the top vegetable sources include green beans and peas. Organic/non-GMO corn, leafy greens, onions, sweet potatoes, many legumes/beans, nuts, seeds, and whole grains like barley are also iodine-rich foods.
Do bananas have iodine? Yes, although they do not contain as much as dried fruits like prunes and raisins.
Berries, including strawberries, also contain some.
Keep in mind that iodine levels vary greatly within a type of food depending on the conditions in which it was grown or produced. For example, because soil depletion is a concern for lowering iodine counts in foods, crops grown in depleted soils have lower levels of iodine than organically grown crops.
Similarly, wild-caught seafood and cage-free, organic eggs are more likely to contain higher levels of nutrients than farm-raised fish or conventionally produced versions.
Iodine Health Benefits
1. Supports Thyroid Health
The thyroid must have high enough levels of iodine present in order to make key hormones, including thyroxine.
Thyroid hormones regulate many important biochemical reactions every day. Some of the most significant include the synthesis of amino acids from proteins, digestive enzyme activity, and proper skeletal and central nervous system development.
When thyroid disorders such as hypothyroidism occur because of a diet low in iodine-rich foods, symptoms can range from a sluggish metabolism to heart complications, changes in appetite and body temperature, alterations in thirst and perspiration, weight fluctuations, and mood changes.
Acquiring enough of this mineral is also important for preventing goiters, or an enlarged thyroid, as well.
2. May Help Prevent Cancer
Iodine improves immunity and helps induce apoptosis — the self-destruction of dangerous, cancerous cells. While it can help destroy mutated cancer cells, it doesn’t destroy healthy cells in the process.
For example, evidence shows the ability of iodine-rich seaweed to inhibit certain types of breast tumor development. This is supported by the relatively low rate of breast cancer in parts of the world like Japan, where women consume a diet high in seaweed.
Specific types of iodine treatments are also sometimes used to help treat thyroid cancers.
3. Supports Growth and Development in Children
Iodine is most critical in the early stages of development, as a fetus’ brain tissue and thyroid receptors are extremely dependent on this mineral to form normally.
Research shows that an iodine deficiency during pregnancy and infancy can disturb healthy growth and brain development. Infants with iodine deficiency are more susceptible to mortality and at a higher risk for neurodegenerative problems — like a form of mental disability known as cretinism — low growth rate, motor-function problems and learning disabilities.
Although doctors commonly test women during pregnancy for iodine deficiency, it’s difficult to get an accurate reading of iodine levels. Thus, many health experts now encourage women to increase their intake of iodine-rich foods in their pregnancy diet and supplement with iodine considering how common deficiencies are.
4. Maintains Healthy Brain Function
Studies show that iodine plays a role in healthy brain development and ongoing cognitive abilities — therefore deficiency is thought by experts to be one of the most common preventable causes of mental disorders in the world, as well as neurodegenerative impairment.
Some of the ways that it supports cognitive health include by facilitating brain development during specific time windows influencing neurogenesis, neuronal and glial cell differentiation, myelination, neuronal migration, and synaptogenesis.
5. Preserves Skin Health and Fights Infections
A common sign of iodine deficiency is dry, rough and irritated skin that becomes flaky and inflamed. This mineral also helps regulate perspiration, so people might experience changes in how much they sweat if their levels become imbalanced.
Another benefit is potentially helping to treat minor infections, such as those that form in scrapes, when applied topically since it has natural antibacterial properties.
6. Helps Control Sweating and Body Temperature
Sweating is an important detoxification method that the body uses to discard toxins and even excess calories. Iodine deficiency can disturb the natural way we flush waste from the body through our pores and control our body temperatures.
Similar to an ability to produce enough sweat, a lack of iodine also can cause dry mouth due to an abnormally low production of saliva. This makes it difficult to enjoy eating and can impair digestion to some degree.
Iodine Deficiency
Worldwide around 2 billion people are estimated to suffer from insufficient iodine intake, although many are unaware because they don’t display symptoms. Populations in South Asia and sub-Saharan Africa are particularly affected.
In the U.S. and Europe, deficiency is believed to be on the rise.
Common signs of an iodine deficiency include:
- Trouble producing saliva and properly digesting food
- Swollen salivary glands and dry mouth
- Skin problems, including dry skin
- Poor concentration and difficulty retaining information
- Muscle pains and weakness
- Increased risk for thyroid disease
- Increased risk for fibrosis and fibromyalgia
- A higher risk for developmental problems in babies and children
Although too much iodine is a potential risk for thyroid disruptions, it’s much less common and considered a relatively small risk compared to the substantial risks of deficiency. Plus, consuming very high levels from foods high in iodine alone is very unlikely.
Due to the high prevalence of iodine deficiencies globally, plus the serious health concerns as a consequence, there is much more emphasis in the health community on adding more of this mineral into the average person’s diet than worrying about removing it.
Why are more people experiencing iodine deficiency?
Several reasons might be to blame, including:
- A reduction in dietary iodine intake.
- A higher exposure rate to certain chemicals found in processed foods that reduce iodine absorption (especially the compound called bromine, found in many plastic containers and baked goods, for example).
- A depletion in the amount of iodine found in soils.
Bromine, found in lots of industrial-produced packaged food products, is of particular interest to researchers, since it’s known to block foods rich in iodine from being useful and absorbable to some degree. Bromine is able to displace iodine and might lead to higher rates of iodine deficiency.
When it comes to soil depletion, research points to the fact that, around the world, soils contain varying amounts of iodine, which in turn affects the quantity of this mineral within crops. In some areas, mineral deficient soils are more common, which makes it more likely that people will develop deficiencies.
Efforts to reduce deficiencies, known as “salt iodization programs,” help reduce the rate of deficiency in some parts of the impoverished world that experience high rates of ill health effects. But the surest way to prevent deficiencies (and the safest) is to increase your intake of iodine-rich foods.
Supplements and Dosage
Low iodine status and diets low in foods with iodine are associated with an increased risk for thyroid disease, but there are also potential thyroid and hormonal risks associated with taking too much iodine, especially from supplements that contain it in the form of iodide.
Although it seems counterintuitive, research suggests that consuming more than the suggested amount per day is even associated with an increased risk for thyroid disorders as opposed to preventing them.
Recommended daily intake:
Iodine recommendations are given in terms of “dietary reference intakes” (DRIs). DRIs were developed by the Food and Nutrition Board at the Institute of Medicine of the National Academies as a set of values used for planning and assessing nutrient intakes of healthy people.
According to the USDA, the recommended amount of iodine depends on your age and gender and are as follows:
- Birth to 6 months: 110 micrograms
- 7–12 months: 130 micrograms
- 1–8 years: 90 micrograms
- 9–13 years: 120 micrograms
- 14 years and older: 150 micrograms
- Pregnant women: 220 micrograms
- Breastfeeding women: 290 micrograms
How can you best meet these recommended amounts? Eat more foods rich in iodine, especially the kind that naturally contain this mineral and aren’t fortified.
Recipes
Including seaweeds and algae in your diet is one of the best ways to boost your intake, considering their high iodine content — along with other important minerals and antioxidants they contain.
Various forms of seaweed (such as kelp, nori, kombu and wakame) are some of the best, natural sources of iodine. Like all crops, however, the exact content depends on the specific food and where it came from.
Other good iodine-rich foods include seafood, raw/unpasteurized dairy products, certain whole-grain products and cage-free eggs. It’s believed that dairy products and grains are the major contributors of iodine in the average American’s diet, although chances are people can afford to consume more raw, unpasteurized dairy and ancient, whole grains rather than conventional dairy and packaged foods.
To some extent, fruits and vegetables also contain iodine. The amount depends a lot on the soil, fertilizer and irrigation practices used to grow the crops.
Because high-quality meat and dairy products come from animals raised on grass and given healthy diets, the amount of iodine in animal foods also varies depending on the quality of their diets and where they were free to graze.
Risk and Side Effects
As mentioned earlier, too much iodine can lead to thyroid disorders because it has the potential for causing goiters on the thyroid just like an iron deficiency does. People who have Hashimoto’s disease, thyroiditis or certain cases of hypothyroidism should speak with their doctors to discuss how much, if any, iodine should be taken through supplements carefully.
Are iodine salts and supplements healthy?
According to the USDA, more than 70 countries, including the United States and Canada, have public health salt iodization programs, and 70 percent of households worldwide use iodized salt.
The intentions of iodizing salt originally was to prevent deficiencies, so in the U.S. manufacturers started adding iodine to table salt in the 1920s.
The U.S. Food and Drug Administration approves potassium iodide and cuprous iodide for salt iodization, and the World Health Organization recommends the use of potassium iodate due to its greater stability.
On average, about 45 micrograms of iodine can be found in each eighth of a teaspoon of iodized salt in the U.S.
By law, food manufacturers almost always use non-iodized salt in processed foods and list salt as iodized in the ingredient list on foods that use iodized salt. The reason is to prevent very high intakes of iodine, considering the majority of salt intake in the United States comes from processed foods.
It’s best to consume real salt, either Himalayan or Celtic sea salt, as opposed to iodized table salt. Sea salt contains more than 60 trace minerals and doesn’t pose a risk for overconsuming iodine like table salt does. It’s also much more natural, beneficial and tastes better.
Many supplements also contain iodine in the forms of potassium iodide or sodium iodide, including many multivitamins. Kelp capsules also contain iodine.
These usually aren’t necessary when someone consumes enough iodine-rich foods and may even be dangerous if taken in high doses. Taking supplements within the recommended daily amount can be helpful and is considered safe, but it’s also best to follow dosages carefully and aim to get nutrients from food whenever possible.