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 increase your iodine levels? The very best way to maintain a normal iodine status is by eating foods high in iodine.
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 contains up to 2,984 mcg (1,989% Daily Value*)
- Dried wakame — two tablespoons contains 420 mcg (300% DV)
- Baked cod — 3 ounces contains 146 mcg of iodine (97% DV)
- Nori seaweed — 2 tablespoons (flaked) contains 116 mcg (77% DV)
- Oysters, cooked — 3 ounces contains 93 mcg (62% DV)
- Greek yogurt, nonfat plain — ¾ cup contains 87 mcg (58% DV)
- Milk, nonfat — 1 cup contains 84 mcg (56% DV)
- Iodized table salt — ¼ teaspoon contains 78 mcg (52% DV)
- Egg, hard boiled — 1 large contains 31 mcg (21% DV)
- Lima beans, cooked — 1 cup contains 16 mcg (10% DV)
- Cheddar cheese — 1 ounce contains 14 mcg (9% DV)
- Beef liver, cooked — 3 ounces contains 14 mcg (9% DV)
- Shrimp, cooked — 3 ounces contains 13 mcg (9% DV)
- Prunes — 5 prunes contain 13 mcg (9% DV)
- Corn, cooked — half-cup contains 14 mcg (9% DV)
- Tuna, canned in water, drained — 3 ounces contains 8 mcg (5% DV)
*Daily Value: Percentages are based on a diet of 2,000 calories a day.
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.
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.
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.
Conclusion
- Iodine is an essential mineral that enters the body through certain foods and salts.
- 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.
- Unfortunately, many people are deficient in this mineral, which makes consuming iodine-rich foods all the more important.
- Low iodine intake can lead to symptoms such as poor digestion, dry mouth, skin problems, poor concentration, muscle pains, weakness and others.
- The best way to safely increase your iodine intake is to consume foods rich in iodine, such as egg, algae, vegetables, beans and fish.
