Iodine Supplement


It’s important to know what the best iodine supplement is in order to get the most for your money. We’re going to cover everything – including my favorites and why I chose them.

Iodine deficiency continues to be one of the most common and widespread nutrition problems in the world. In the United States, an estimated 57 percent of the population is deficient in iodine. As with many nutritional deficiencies, low levels of iodine can lead to serious health issues. The only way to tell if you are deficient in iodine is a simple blood test. This article will discuss why you may be deficient in iodine, what symptoms a deficiency may cause, what supplements can do to lower your risk and more.

Iodine Supplement

Iodine is an essential mineral that plays an important role in maintaining the health and function of your thyroid gland.

The thyroid gland is a butterfly-shaped organ located in your neck that produces specific hormones that help regulate growth and metabolism (1Trusted Source).Iodine functions as a building block of the two main thyroid hormones — triiodothyronine (T3) and thyroxine (T4) (2Trusted Source).If your intake of iodine is too low, you can end up with low levels of thyroid hormone in your blood.Insufficient levels of thyroid hormones can lead to symptoms like neck swelling, fatigue, dry skin, hair loss, difficulty regulating body temperature, and weight gain (1Trusted Source).Iodine is naturally found in a variety of foods, such as seafood, dairy products, eggs, and may also be found in grains and some fruits and vegetables. However, the exact amount is primarily dependent upon the iodine levels of the soil in which the crop was grown (1Trusted Source).

Given the variability in iodine levels in many plant-based foods, some countries have iodine-fortified foods available, such as iodized salt, to prevent deficiencies.Even so, certain groups of people are at an increased risk of iodine deficiency, including (1Trusted Source):

  • people who are pregnant
  • people living in places where the soil is iodine-depleted
  • people following strict vegan and vegetarian diets
  • people who avoid or have limited access to iodized salt

If you have difficulty getting enough iodine in your diet, your healthcare provider may recommend that you take an iodine supplement.

The supplements on this list were chosen according to ingredient quality, price, and manufacturing standards.

11 Best Vegan Iodine Supplements That Work (2021 Review)

Here are the 11 best iodine supplements for 2021.

1. A note on price

General price ranges with dollar signs ($ to $$$) are indicated below. One dollar sign means the product is rather affordable, whereas three dollar signs indicate a higher price range.

Generally, prices range from $0.06–$2.32 per serving, or $8–$69.70 per container, though this may vary depending on where you shop.

Note that serving sizes vary by product.

If you’re looking for a basic, high quality iodine supplement, look no further, as these are among the best on the market.

2. Pure Encapsulations Iodine

Each of Pure Encapsulations’ iodine capsules provides 225 mcg of iodine, or 150% of the Reference Daily Intake (RDI), in a highly absorbable form called potassium iodide.

When it comes to quality, Pure Encapsulations is an industry leader. All of their raw materials and finished products are third-party tested for purity and potency, so you can rest assured you’re always getting what you have paid for.

These capsules are vegan and free of most major allergens, including gluten, wheat, egg, nuts, and artificial colors and sweeteners.

3. Thorne Iodine and Tyrosine

Thorne is a reputable brand known for producing a variety of high quality, allergy-friendly nutritional supplements.

Its iodine supplement is designed to support thyroid health using a combination of 225 mcg of potassium iodide, or 150% of the RDI, and 500 mg of tyrosine — an amino acid your body uses to produce thyroid hormones (2Trusted Source).

This supplement is free of sugar, artificial sweeteners, and major allergens like gluten, wheat, tree nuts, dairy, and soy.

All of Thorne’s nutritional supplements are tested for purity and potency, and their manufacturing facilities are certified by multiple regulatory agencies, including NSF International and the Therapeutic Goods Administration (TGA).

4. Standard Process Prolamine Iodine

Standard Process’ Prolamine Iodine supplement provides 600 mcg of iodine, or 400% of the RDI, and 30mg of calcium in each capsule.

The iodine comes from a combination of kelp and Standard Process’ proprietary potassium iodide and cornmeal whole food complex. It’s vegan and gluten-free.

Standard Process prides itself on its high manufacturing standards. Each of their supplements is tested for purity and potency an average of six times before it’s sent to market.

Keep in mind that this supplement contains about 2% of the RDI of calcium. This is not harmful for most people, but if you’re already taking a calcium supplement, you may be at a slight risk of consuming too much.

Calcium supplements may also interfere with the absorption of certain prescription thyroid medications if they’re consumed at the same time.

Thus, you should consult your healthcare provider before adding it to your routine.

Some people may benefit from supplementing with high doses of iodine short term, and these are some great options to choose from.

Keep in mind that you should not attempt to take exceptionally high doses of iodine without guidance from a qualified healthcare provider.

5. Life Extension Sea-Iodine

Each of Life Extension’s Sea-Iodine capsules provides 1,000 mcg of iodine, or 667% of the RDI, sourced from a combination of kelp and potassium iodide.

All of Life Extension’s ingredients are meticulously studied, and their final products are manufactured in facilities certified by NSF International, so you know you’re always getting a high quality supplement.

For the sake of transparency, Life Extension also provides you a certificate of analysis for every batch of supplements they produce, so you can see exactly what’s in the product you’ve purchased.

6. Swanson Triple Iodine Complex

Swanson’s Triple Iodine Complex supplement provides a high dose of 12,500 mcg of iodine, or 8,333% of the RDI, in the form of potassium iodide, sodium iodide, and kelp-derived iodine.

All of Swanson’s supplements are tested for purity and potency in-house, as well as by third-party laboratories. What’s more, all of their manufacturing facilities are certified by the Food and Drug Administration (FDA).

7. Designs for Health Iodine Synergy

Designs for Health’s Iodine Synergy supplement contains 10,000 mcg of iodine, or 6,670% of the RDI, in the form of potassium iodide, plus 40 mcg of selenium, a nutrient that functions as an antioxidant and aids thyroid hormone metabolism (3Trusted Source).

It’s vegetarian-friendly and free of most major allergens, including dairy, soy, and gluten. It also comes in a glass bottle for easy recycling.

Designs for Health is a reputable brand that maintains stringent quality standards during each step of the manufacturing process. All products are tested for purity, potency, and safety, and all of their production facilities are FDA certified.

Seaweed is one of the richest natural, plant-based sources of iodine.

If you prefer taking supplements sourced from whole food ingredients, you may want to try one of these options, which are made exclusively with iodine from a type of seaweed known as kelp.

8. Peak Performance Whole Food Kelp Iodine

Peak Performance’s iodine supplement provides 150 mcg of iodine, or 100% of the RDI, sourced exclusively from organic kelp.

Its vegan-friendly and free of most major allergens, including tree nuts, fish, shellfish, eggs, wheat, and gluten.

No additives, fillers, or sweeteners are added to the supplement, and all of this company’s products are third-party tested for purity, though the name of the testing company is not disclosed for proprietary reasons.

9. NOW Kelp

NOW is a popular supplement brand that boasts an affordable price point without compromising quality.

Its vegan-friendly kelp supplement contains 150 mcg of iodine, or 100% of the RDI, sourced exclusively from whole organic kelp.

All of NOW’s manufacturing facilities are FDA approved, and all of its supplement ingredients undergo rigorous testing for purity and potency.

Best for pregnancy

Iodine is a very important nutrient for sustaining a healthy pregnancy.

Prenatal supplements contain vastly different types and quantities of nutrients, but many do not contain iodine at all.

An article published in the journal of the American Academy of Pediatrics states that although most pregnant and nursing mothers take prenatal supplements, only 15–20% are taking one that contains iodine (4).

Here are two high quality options that do.

10. GLOW Prenatal

Each serving of GLOW’s prenatal capsules provides 150 mcg of iodine, or 68% of the RDI during pregnancy, alongside more than 20 other nutrients that support healthy prenatal development.

GLOW always uses the highest quality, most absorbable nutrient forms, and all of their products are third-party tested for purity and potency.

The U.S. Dietary Guidelines recommend that people who are pregnant consume at least 220 mcg of iodine per day (1Trusted Source).

Thus, if you choose GLOW as your prenatal supplement, you still want to make sure you’re including iodine-rich foods in your diet to meet your daily needs.

Supplements are designed to fill nutrient gaps, but a balanced diet is still an integral part of a healthy pregnancy.

11. Smarty Pants Prenatal Gummies

Note: Though this product receives three dollar signs based on its list price, some retailers may offer significant discounts.

Smarty Pants’ prenatal gummies are a great option if you’re pregnant and have difficulty tolerating regular capsules.

All of Smarty Pants’ products are third-party tested for purity, so you don’t have to worry about them containing any contaminants or potentially harmful ingredients that are not listed on the label.

Smarty Pants does not disclose its third-party laboratory for proprietary reasons, but you can access certificates of compliance for each supplement on the company website.

You get 290 mcg of iodine, or 132% of the RDI during pregnancy, in each 4-gummy serving.

The gummies are sweetened with a combination of cane sugar and tapioca syrup, but they only contain 6 grams of added sugar per serving.

They’re free of artificial sweeteners and naturally colored with fruit and vegetable juices. The company also offers an organic version for anyone who prefers organic supplements.

How to choose

When choosing a nutritional supplement, you’ll want to consider a variety of factors, including the price, quality, ingredient content, and dosage.

Certain brands are more expensive than others, but price isn’t necessarily a good indicator of quality.

In certain countries, such as the United States, nutritional supplements are not as tightly regulated as medications.

Thus, the safest option is to stick with supplements that are produced by reputable companies that maintain high manufacturing standards and routinely test their products for purity and potency.

You also want to inspect the ingredient label. If there are any specific ingredients you’re avoiding, such as added sugar, animal products, artificial sweeteners, or allergens, always check the ingredient list before purchasing.

Finally, you want to evaluate the dosage.

Supplements often contain more than the recommended daily amount of a nutrient, so you want to be careful you don’t accidentally consume too much.

Conversely, if your healthcare provider recommends that you take a high dose, make sure you choose one that provides an adequate amount to meet your needs.

Iodine Supplementation: Usage

Iodine | Breastfeeding | CDC

Iodine supplementation through salt iodization is a worldwide, effective strategy for preventing iodine deficiency-related problems. Its safety and efficacy profile has been extensively investigated, and benefits far outweigh the potential iodine-induced risks. Moreover, iodine supplementation during pregnancy in order to avoid brain damage in the newborn is considered a mainstay of preventive medicine. Exposure to high amounts of iodine is actually well tolerated in most cases and can be unrecognized. Nevertheless, at-risk individuals may develop thyroid dysfunction even when they are exposed to increases in iodine intake universally considered as safe. Iodine-induced thyroid disorders include thyroid autoimmunity, thyrotoxicosis, iodine-induced goiter, and hypothyroidism. Moreover, a relationship between iodine intake and histotype distribution of differentiated thyroid cancer has been observed, with a progressive shift from follicular to papillary thyroid cancer. To date, evaluating iodine status in a clinical setting has limitations, and assessing the actual risk for each individual can be challenging, since it is influenced by personal history, genetics, and environmental factors. In conclusion, iodine supplementation programs need to be continued and strengthened, but iodine should be used “with a grain of salt,” because a growing number of susceptible individuals will be exposed to the risk of developing iodine-induced thyroid disorders.

1. Introduction

Iodine deficiency is a significant public health problem and worldwide efforts have been made over the past 80 years in order to eliminate this condition. However many countries, including some developed nations, are still considered to be moderate to mild iodine-deficient and billions of people remain at risk for iodine deficiency all over the world. Iodine supplementation through salt iodization is an effective and sustainable strategy for preventing iodine deficiency [1, 2]. Many countries have adopted salt fortification programs and the most extreme manifestations of iodine deficiency are becoming increasingly rare. Nonetheless, iodine deficiency is still a major public health problem, with pregnant women, infants, and school-age children being the most vulnerable categories.

Iodine deficiency-related problems are well known (hypothyroidism, goiter, and hypothyroidism-related brain damage in the newborns), but iodine excess-related thyroid disorders can be a clinical problem as well.

Most people are highly tolerant to iodine and can be chronically exposed to massive amounts of iodine without developing apparent side effects [3]. Table 1 reports the recommended daily allowance (RDA) and the upper intake levels (ULs) for iodine proposed by two institutions: the Health & Consumer Protection Directorate-General of the European Commission [4] and the Food and Nutrition Board of the U.S. Institute of Medicine of the National Academies [5]. ULs are defined as the highest daily intake levels that are unlikely to cause health problems in most of the individuals.

The aim of this review is to assess potential risks deriving from both physiological iodine exposure and above-physiological iodine exposure and to identify at-risk groups who are susceptible to high iodine exposure in order to predict, prevent, early detect, and treat iodine-induced thyroid disorders.

2. Iodine Exposure and Potential Development of Thyroid Disease

Risk for thyroid disease deriving from iodine exposure is U-shaped: this indicates that potential harm for the subject can derive from both iodine deficiency and iodine excess [6]. This relationship and the actual risk for each individual are influenced by many variables: age, gender, genetic predisposition, environmental factors, personal history of thyroid diseases, concurring diseases, and some medications. Thus it can be difficult to assess the actual risk for every single person.

Natural and artificial iodine sources are many, and exposure to “more than adequate” or “excessive” iodine levels can occur quite unknowingly. Exposure to very high doses of iodine may cause significant thyroid dysfunction in susceptible individuals. This predisposition resides broadly in a dysfunction of the self-regulatory mechanisms of thyroid hormone biosynthesis, which protect the thyroid gland from the fluctuations of iodine intake and from iodine overload. However, thyroid dysfunction can occur in patients with no history of thyroid disease.

Iodine supplementation through salt iodization is universally considered as a safe prevention strategy. It aims at exposing populations to physiological iodine amounts, and the potential risk of causing “more than adequate” or “excessive” iodine intake is low. However, evidence exists about iodine-induced thyroid disorders in areas with long-standing iodine deficiency where salt iodization is introduced or increased according to controlled prevention national programs.

Rather new sources of iodine are dietary supplements (such as kelp), multivitamins, and over-the-counter (OCT) drugs. National regulations regarding these drugs may vary substantially, and the product labeling can be misleading. In fact, some food supplements [8], prenatal multivitamins [9], and OCT drugs [10] have been proven to contain very high doses of iodine (up to several milligrams of elemental iodine/day), and actual iodine content can be higher than the one reported by the product labeling. The American Thyroid Association (ATA) has recently released a statement advising against the ingestion of dietary supplements containing >500 μg of iodine daily (considering an UL for iodine of 1,100 μg/day) [11].

3. How to Assess Iodine Intake

It is very important to stress the difference between taking “adequate,” “more than adequate,” and “excessive” iodine. The World Health Organization (WHO) uses the median urinary iodine excretion (UIE) to define “excessive” iodine intake in the overall population (Table 2): median UIE > 300 μg/L (for general population) and >500 μg/L (for pregnant women) are considered “excessive” and should be avoided for the potential adverse effects on health.

Moreover, the WHO points out that median UIE > 200 μg/L should be avoided in populations characterized by long-term iodine deficiency that are exposed to significant increase of iodine intake [7]. In particular, these populations may be at risk for developing iodine-induced hyperthyroidism, since the thyroid has become very efficient in taking up and processing even small amounts of iodine. Recent national surveys based on median UIE showed that the number of countries with “more than adequate” or even “excessive” iodine intake has increased over the past years, indicating that a growing number of susceptible individuals are exposed to the risk of developing iodine-induced thyroid dysfunction [1].

In common clinical practice, spot urinary iodine values are generally used to assess iodine status. Nonetheless, there is substantial diurnal and day-to-day variation in UIE, and less than ten urine samples in an individual may be misleading [12]. Therefore, UIE is more useful for groups and population studies than for individuals.

Thyroid volume can be used as another parameter to evaluate iodine status in the general population. It tends to decrease after months/years of iodine supplementation in previously iodine-deficient communities, as shown in school-age children in Côte d’Ivoire [13]. Thyroid size and goiter volume can be easily assessed by ultrasound according to international reference values [14], and goiter shrinkage can be considered a sensitive long-term indicator of iodine sufficiency. Anyway, to date thyroid volume cannot be used to assess “more than adequate” or “excessive” iodine intakes.

Serum thyroglobulin (Tg) has been proposed as an alternative biomarker to assess iodine intake. A rise in thyroid-stimulating hormone (TSH) caused by iodine insufficiency can be responsible, indeed, for enhanced Tg production and cleavage: this leads to increased serum Tg levels. 13 μg/L has been proposed as a cut-off serum Tg level to distinguish between insufficient and adequate iodine intake, especially in school-age children [15]. Anyway, data regarding adults and pregnant women are conflicting and large national and international randomized placebo-controlled trials are needed to assess the role of serum Tg as a biomarker of iodine intake in the general population. To date Tg cannot be used to as a biomarker to establish “more than adequate” or “excessive” iodine intakes.

4. Iodine “Excess” and Risk of Thyroid Autoimmunity

Iodine “excess” is an environmental risk factor for the development of thyroid autoimmunity, both in genetically prone animal models (such as the nonobese diabetic, NOD, mouse) and human population studies [16]. Iodine seems to stimulate thyroid autoimmune damage in a dose-dependent manner, and several mechanisms have been advocated (Figure 1).

Iodine excess can enhance oxidative stress of thyrocytes by activation of the reactive oxygen species (ROS) cascade, which is normally required for iodine oxidation and organification [17]. This is possibly caused by a latent alteration of intracellular processing of iodine, which is unmasked by iodine overload. This may lead to cellular injury (including apoptosis or necrosis) and proinflammatory changes in genetically prone thyroid tissue, such as increased cytokine and chemokine production [18, 19], major histocompatibility complex (MHC) class II expression [20], and intercellular adhesion molecule (ICAM)-1 expression [21] on thyrocytes. Moreover, excess iodine can change the 3D structure of Tg either by greater iodine organification [22] or by ROS-mediated Tg proteolysis [23]. As a consequence Tg autoantigenicity increases, leading to attraction of immunocompetent cells to the thyroid. All these changes are potential triggers for the development of thyroid autoimmunity, both as immune cell thyroid infiltration and autoantibody production. Both tissue infiltration and autoantibody production can be stopped by silencing CD4+ T lymphocyte, CD8+ T lymphocyte, or B lymphocyte response [24], indicating a pivotal role of lymphocytic infiltration in the development of iodine-induced autoimmune thyroiditis.

Several human population studies have shown a positive correlation between iodine exposure and the development of autoimmune thyroiditis. Li et al. [25] have shown an increased incidence of anti-Tg antibodies during a 5-year follow-up in a Chinese region with chronic excessive iodine exposure, and high iodine intake was a risk factor for developing hypothyroidism in antibody-positive subjects. Moreover, iodine prophylaxis has been put in relation to a higher incidence of Hashimoto’s thyroiditis in Italy [26], antithyroid peroxidase (TPO) antibody positivity in Polish adults [27], and anti-Tg antibody positivity in female school-age children in Sri-Lanka [28]. A gradual increase of the incidence of Hashimoto’s thyroiditis was also observed in Slovenia [29] after increase in salt iodization from 10 to 25 mg of potassium iodide per kg of salt in 1999. Finally, a study from Greece [30] shows how the shift from iodine insufficiency to adequate or excessive iodine intake has been accompanied by a higher rate of thyroid autoimmunity, mainly in young women. The prevalence of autoimmune thyroiditis in school-age children raised from 3.3% in 1994 to 9.6% in 2001, and the association between higher UIE and autoantibody positivity was significant.

5. Iodine “Excess” and Risk of Thyrotoxicosis

Excessive iodine intake may be responsible for iodine-induced thyrotoxicosis (Jod-Basedow phenomenon), caused by iodine action on thyrocytes whose function is TSH-independent. Therefore, susceptible subjects are patients with Graves’ disease (even if in remission or under medical treatment) and patients with nodular goiter living in iodine-deficient areas. The first group usually includes younger subjects with diffuse goiters and detectable thyroid-stimulating antibodies (TSAb). On the other hand, the second group consists of older subjects with undetectable TSAb and nodular goiters which harbor areas of functional autonomy.

As a consequence, living in moderate to mild iodine-deficient areas is a risk factor per se for the development of thyrotoxicosis if the population is exposed to a sudden increase of iodine intake. The actual extent of this phenomenon depends on the duration of iodine deficiency, on the severity of iodine deficiency, and on the degree of iodine load [31]. By far the best documented epidemic of iodine-induced thyrotoxicosis occurred in Tasmania in the late 1960s and beyond [32], after the introduction of iodized bread and iodophors in the dairy industry and after increasing distribution of iodine-rich foods imported from Australia. Thyrotoxicosis was most evident in older subjects (>40 y.o.). Similar results have been observed in Austria after an increase in salt iodization in 1990 from 10 to 20 mg of potassium iodide per kg of salt [33]. An increase of cases of hyperthyroidism was observed, peaking 1–4 years after the enhancement of iodine prophylaxis: toxic nodular goiter was responsible for 75% of all cases, whereas Graves’ disease accounted for 19%. The preferential incidence of iodine-induced thyrotoxicosis among older subjects can be responsible for a higher rate of complications, such as cardiac arrhythmias and heart failure.

However, the incidence of iodine-induced thyrotoxicosis tends to decrease over time after the introduction of iodine supplementation. In fact, prophylaxis is expected to reduce the number of patients with toxic nodular goiter, which are susceptible to the Jod-Basedow phenomenon.

6. Iodine “Excess” and Risk of Iodine-Induced Goiter and Hypothyroidism

A chronic exposure to iodine excess can lead to the development of goiter, with or without hypothyroidism. Rarely, hypothyroidism without goiter can occur.

Two different pathogenic mechanisms have been advocated: direct, iodine-induced toxic damage of thyrocytes and loss of the “escape” phenomenon after the Wolff-Chaikoff effect, which is a physiological response likely due to downregulation of sodium-iodide symporter (NIS) (Figure 2).

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