Amount of Evidence: High Potential Benefits: Reasonable Safety: High
TABLE OF CONTENTS
What is iodine?
Iodine is a trace mineral and an essential nutrient, found primarily in seaweed, iodized salt, and certain types of fish and seafood. In the body, the mineral is mainly responsible for making thyroid hormones. This article is about the main benefits of taking iodine, its potential side effects, the best time to take it, and more.
Potential benefits
It is important to note that all of the potential benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.
Major benefits
Correcting an iodine deficiency – Iodine deficiency can be terrible for your health and overall quality of life. Fortunately, a severe deficiency is relatively rare. A mild deficiency is much more common and can cause hypothyroidism, which can lead to many problems mentioned later in the article. If you are experiencing symptoms of deficiency or know that your iodine levels are too low, correcting a deficit is the main benefit of iodine supplements.
Minor benefits
Reduced rates of infections – Iodine is used topically as a disinfectant to treat wounds or sterilize industrial equipment. It may act the same way inside the body. Having high levels of this nutrient may partially protect us from dangerous microbes.
Inflammation – The mineral appears to lower CRP (C-reactive protein), one of the main biomarkers of inflammation. The supplement may have anti-inflammatory properties even if you are not deficient in the nutrient.
Fibrocystic breast disease – Iodine may improve the tenderness associated with fibrocystic breast tissue, especially for people with low levels of the mineral.
Protection from radioactive iodine – Radioactive iodine gets released in nuclear accidents. High doses of non-radioactive iodine can block the uptake of radioactive iodine in the thyroid.
Unproven benefits
There is not enough evidence that iodine notably affects these health metrics, or the science shows little to no efficacy in these areas.
Skin quality – Unfortunately, the supplement does not seem to help with acne, wrinkles, or other skin problems. It also doesn’t help hydrate the skin or keep it elastic.
Blood flow – Scientific studies have never shown a significant effect on blood flow.
Blood pressure – There is no high-quality evidence that the supplements affect blood pressure to any significant degree.
DNA protection – The supplement has not been shown in human studies to protect DNA from oxidative damage.
Triglycerides – There is no significant influence, or at least it has never been observed.
Brain health and cognition – The supplement does not directly improve brain health and cognitive abilities.
Testosterone – The supplement does not significantly affect DHT, free testosterone, or total testosterone levels.
Cholesterol – The supplement has no direct effect on HDL or LDL cholesterol levels.
Cancer – The supplement has never been shown in reliable human studies to affect cancer rates or tumor growth.
Well-being – Supplementation with the mineral doesn’t appear to increase subjective well-being. However, the supplement could improve your well-being if you are deficient in iodine.
Weight loss and fat loss – Taking the supplement doesn’t notably affect weight loss or burning of fat.
Strength and muscle growth – The supplement does not help you increase strength or muscle mass faster. Reliable human studies have never shown this effect.
Asthma – The supplement has not been shown to help with asthma to a significant degree.
Power output during exercise – The supplement does not directly influence power output during aerobic or resistance training. It does not impact VO2 max or aerobic endurance either.
Kidney function – The supplement does not significantly change kidney function biomarkers.
Sleep quality – The supplement does not directly improve sleep quality. It also does not seem to affect sleep duration.
Stress and anxiety – The supplement does not affect cortisol levels, at least not directly.
Metabolic rate – The supplement does not speed up your metabolism or slow it down.
Possible side effects
These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.
Iodine toxicity – While toxicity is rare, taking high amounts of the mineral could lead to some health problems over time. For example, over 18,000 mcg/d can cause goiter. Extremely high doses (in grams) could also lead to abdominal pain, fever, nausea, vomiting, and coma. It’s best to avoid very high doses since they do not appear to be safe to take over a long period. Specifically, you want to stay below 1000 mcg a day.
Worsened Hashimoto’s disease – Doses as low as 200 mcg daily have been shown to worsen symptoms of Hashimoto’s thyroiditis and Grave’s disease, autoimmune conditions that involve the body attacking its thyroid gland. The supplement may not be safe if you have one of these conditions.
Worsened thyroid health – Doses higher than 1000 mcg taken daily over a long period can negatively change blood markers of thyroid health. However, this may not be a concern since some cultures eat as much as 15000 mcg daily without any apparent side effects.
Contamination – Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, the supplement companies can change their manufacturers at any time without announcing it to the FDA.
Who should not take iodine?
You should probably avoid taking the supplement if you:
already consume enough of the mineral from food or salt
experience a severe adverse reaction after taking the supplement
suffer from Hashimoto’s thyroiditis (doses as low as 200 mcg daily have been shown to worsen symptoms of Hashimoto’s disease)
suffer from Grave’s disease (the same said about Hashimoto’s also applies to Grave’s disease)
are on a tight supplement budget (since there are more cost-effective supplements on the market)
Who will benefit the most?
You should consider taking the supplement if you:
experience symptoms of deficiency, or you know you are deficient based on blood tests
avoid iodized salt and don’t get enough iodine from food
suffer from fibrocystic breast disease
regularly swim in chlorinated swimming pools (since chlorine might interfere with iodine function)
get exposed to flame retardants, dyes, insecticides, furniture foam, gasoline, and the casings of electronics (since bromine in these things also interferes with iodine function)
get exposed to high levels of radiation with radioactive iodine
Forms of iodine supplements
The forms of iodine supplements include:
Kelp – This is the most natural form and probably the best one to take. Kelp supplements contain other beneficial compounds, such as fucoxanthin and fucoidan.
Other types of seaweed – Nori, wakame, bladderwrack, and other types of seaweed can also be sold as dietary supplements. These types contain significantly less iodine per gram. That is not necessarily bad since they usually provide more of the other beneficial compounds like fucoxanthin and fucoidan. The downside of these types is that they tend to be significantly more expensive than kelp.
Lugol’s iodine – This form, also known as aqueous iodine, is a mixture of molecular iodine and potassium iodide. It is purer than kelp supplements.
Iodoral – Iodoral is also a combination of molecular iodine and potassium iodide and its effects are almost identical to Lugol’s iodine.
Nascent iodine – While some people claim nascent iodine can release energy when consumed and provide high doses of the mineral without hurting the thyroid, there is no high-quality scientific evidence to support these claims. This form is likely just as effective as the other forms but not more effective.
Povidone-iodine – This form is used topically or as a nasal spray. You can absorb the mineral through the skin so this form can improve your iodine status. Unfortunately, it is difficult to accurately estimate the dose so povidone is not the best for this purpose.
Potassium iodide – Potassium iodide is the most popular iodide salt. This form is just as effective as the other forms.
Sodium iodide – The effects of this form are virtually identical to those of potassium iodide. The problem is that it may be hard to find sodium iodide supplements. Because sodium iodide is not popular as a dietary supplement, it is not easy to obtain it from regular supplement stores. While you can order pure sodium iodide from chemical companies, it may be risky to do so since chemicals not intended for human use are not nearly as regulated as dietary supplements and are much more likely to contain dangerous fillers. iodide.
Potassium iodate – This form is commonly added to iodized salt. There is not a big difference between iodate salts and iodide salts as far as the effects on the body. As a supplement, this form is also difficult to obtain. Everything said about sodium iodide also applies to potassium iodate.
Of all these forms, kelp appears to be the best one because of the other compounds in the supplement. Other types of seaweed supplements could be even better but are considerably more expensive. All the other forms are roughly equal.
Signs of iodine deficiency
Iodine deficiency is rare in developed countries because of iodized salt and other interventions. With that said, some groups of people are at risk of deficiency.
Counter-intuitively, a deficiency is more common among health-conscious people. That is because many individuals who care about their health tend to avoid iodized salt and eat high amounts of cruciferous vegetables.
The most common symptoms of deficiency include:
Fatigue
Brain fog
Joint pain and stiffness
Swelling in the joints
Stiff muscles and muscle pain
Poor memory
Puffy face
Puffiness under the eyes
High cholesterol
Bloating and constipation
Impaired digestion, especially when it comes to fatty foods
Mood swings and depression
Breast pain
Increased rate of infections
Goiter (an enlarged thyroid gland)
Problems with periods (absent, irregular, or unusually heavy periods)
All of these are connected to and caused by hypothyroidism.
A deficiency is especially concerning during pregnancy and the first few years of life, because it can cause permanent developmental effects. Even mild hypothyroidism in children can cause a lifelong decrease in IQ and other problems.
Keep in mind that these signs are just indications of a deficiency. If you experience some of them, it does not necessarily mean you need more iodine. On the other hand, some people may be deficient even though they are completely asymptomatic.
With that said, if you experience many or most of these symptoms, there is a high chance that you are not getting enough iodine. The more of these symptoms you have and the more severe they are, the more likely you are to have a deficiency.
How much iodine should you take?
The RDA (recommended daily allowance) for iodine is 150 mcg/day for both men and women. Two exceptions are pregnant and breastfeeding women. The RDA for pregnant women is 220 mcg, and for breastfeeding women, it is 290 mcg/day.
Those numbers were based on how much of the mineral the thyroid gland uses each day and how much is lost in the urine. While the daily amount you should be getting depends on multiple factors, 150 mcg is a great estimate.
If you are not getting enough of the mineral from food, 100-150 mcg appears to be the best dose to take for most people. This amount should provide most of the benefits without meaningful side effects. Feel free to experiment with up to 1000 mcg to see if a higher dose makes you feel better.
Certain things may increase your need for iodine. For example, fluoride, chlorine, and bromine all have the potential to interfere with iodine function. Fluoride is mainly found in toothpaste and fluoridated water. Chlorine is mainly found in swimming pools and cleaning products. Bromine is found in flame retardants, dyes, insecticides, furniture foam, gasoline, and the casings of electronics. The more you get exposed to these things, the more iodine you likely need.
Also, compounds known as goitrogens can interfere with the uptake of iodine into the thyroid gland. These are found primarily in fruits and vegetables, most notably in cruciferous vegetables.
Unless you are pregnant, breastfeeding, or trying to correct a severe deficiency, taking more than 150 mcg daily should not be necessary. Also, the higher the dose you take, the higher the risk for side effects.
The upper limit for iodine is 1000 mcg. Do not take more than this amount if you don’t have a great reason to do so.
Food sources of iodine
The iodine content in food highly depends on the soil and how rich the soil is in this nutrient. To put this into perspective, a potato grown in one area can have as much as 100 times more iodine than the same type of potato grown in another place.
So, unfortunately, foods that come from the land are not a good source of iodine because it is difficult to predict how much of the nutrient they contain.
Foods from the sea and ocean are a much more stable source of this trace mineral. While fish and shellfish contain a decent amount, seaweed is by far the richest food source of iodine.
Iodine content in seaweed varies greatly from one type to another. Here are some popular types of seaweed and how much of the mineral they contain per gram of dry weight: – Kelp (1500 mcg/g) – Arame (700 mcg/g) – Bladderwrack (500 mcg/g) – Hijiki (390 mcg/g) – Alaria esculenta (100 mcg/g) – Kelp Granules (67 mcg/g) – Wakame (60 mcg/g) – Nori (45 mcg/g) – Dulse (45 mcg/g)
As far as fish and seafood, the richest sources of iodine are: (the amounts below apply to raw weight, not cooked) – Haddock (250 mcg/100g) – Cod (100 mcg/100g) – Mackerel (130 mcg/100g) – Mussels (110 mcg/100g) – Salmon (60 mcg/100g) – Kippers (50 mcg/100g) – Herring (30 mcg/100g) – Sardines (30 mcg/100g) – Prawns (20 mcg/100g) – Tuna (15 mcg/100g)
Unfortunately, iodine evaporates during the process of making sea salt. This means that natural sea salts do not contain meaningful amounts of the mineral. However, iodine is often added to salt, making it “iodized.” Iodized salt is the main source of the mineral in most western diets. A gram of iodized salt typically contains 20-50 mcg.
The easiest way to find out how much iodine you are getting in your diet is with Cronometer.com – this free app allows you to track all vitamins, minerals, and more.
Best time to take iodine
Since the mineral is water-soluble, it doesn’t make a big difference whether you take the supplement with or without food. The only exception is if you experience stomach upset after taking the supplement, in which case it is better to take it with food.
Also, if you are taking kelp supplements and want to maximize the benefits of the other compounds, such as fucoxanthin, you want to take the supplements with food since many of the compounds in kelp are fat-soluble.
Whether you take the supplement in the morning or the evening doesn’t matter. It does not interrupt your sleep in any way.
Where to buy iodine
Amazon seems to be the best option for ordering iodine supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.
Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.
FAQ
You can take the supplement daily and do not need to cycle it. However, it is certainly not a problem if you don’t take it daily. Not taking the supplement every once in a while could lead to better absorption, but no studies have proven this.
All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, to dose them correctly, you may need a highly accurate scale (preferably 0.001g). You can get one for as little as $20 from Amazon.
Yes. The nutrient doesn’t impact your sleep in any negative way in the short term.
The supplements rarely go bad, but they can lose potency over time.
Keep the supplements in a cold, dark, and dry place, and they will remain just as potent for many months or even years.
Unfortunately, iodine evaporates during the process of making sea salt. That means that natural sea salts do not contain meaningful amounts of the mineral. However, iodine is often added to salt, making it “iodized.” Iodized salt is the main source of the mineral in most western diets. A gram of iodized salt typically contains 20-50 mcg.
While toxicity is rare, too much iodine in the system can cause some health problems, such as goiter. Extremely high doses (in grams) could also lead to abdominal pain, fever, nausea, vomiting, and coma. It is best to stay below 1000 mcg daily to prevent these side effects.
Kelp appears to be the best form of all supplemental forms on the market because of the other compounds in kelp, such as fucoxanthin. Other types of seaweed are also a great choice. All the other forms are roughly equal.
The most common reason people become deficient is that they don’t get enough iodine from their diet. However, other things, such as sulforaphane in cruciferous vegetables, fluoride in water, chlorine in swimming pools, bromine in flame retardants, and other things, may also lead to a deficiency since they increase your need for the nutrient.
You probably need more of the nutrient if you: – experience signs of deficiency, or know that you are deficient from blood tests – get exposed to high levels of radiation with radioactive iodine – regularly swim in chlorinated swimming pools (since chlorine might interfere with iodine function) – suffer from fibrocystic breast disease – avoid iodized salt and don’t get enough iodine from food – get exposed to flame retardants, dyes, insecticides, furniture foam, gasoline, and the casings of electronics (since bromine in these things also interferes with iodine function)
Most of the mineral gets flushed out of your system within 24 hours. A small amount stays in your thyroid gland for much longer.
In the long-term, it typically takes around a month after you start taking the supplement to start noticing benefits.
Yes, most iodine supplements on the market are vegan-friendly.
The nutrient is water-soluble.
No, it does not. The supplement does not interfere with fasting in any significant way.
It does not have a reasonable amount, unfortunately.
References
Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We excluded from consideration studies that are either confounded or have a high conflict of interest.
