Clinical Pearl Wednesday: How Much Iodine Is Too Much?

Jenni Gallagher, APRN

People are prioritizing healthy eating now more than ever, with many dieters looking to social media influencers for nutritional advice. Iodine and iodized salts are the newest foods now demonized by unqualified health coaches, which has triggered detrimental health effects for those with diverse medical needs. Some pop-practitioners recommend replacing iodized salt with “natural” alternatives like rock salts or Himalayan pink salts. This may create significant nutritional gaps, with the potential to cause hypothyroidism. Here, we break down the myths and facts about dietary iodine, and the measurable effects this simple ingredient has on full-body wellness.

The bioavailability of iodized salt

Data suggests that one gram of iodized salt contains approximately 40 to 45 mcg of iodine. Approximately half of this iodine is bioavailable. One teaspoon of salt contains four to six grams of salt with about 240 mcg of iodine. If half of that is available for absorption and use, the body takes in and metabolizes around 120 mcg of iodine.

Some experts report that only 30% of that 45 mcg of iodine is useable, meaning that about 81 mcg of iodine is available per teaspoon of salt consumed. The recommended daily allowance (RDA) of iodine is 150 mcg per day. Using these calculations, approximately two teaspoons of iodized salt are needed to develop significant iodine levels in the body.

Is iodized salt unhealthy?

Mainstream medicine often emphasizes the importance of moderated salt intake, recommending less than one teaspoon per day. However, there is little scientific data to support such a low recommendation. Due to the low bioavailability of iodine in iodized salt, a person may be eating double the recommended serving of salt per day while remaining iodine deficient.

Salt is iodized for a specific reason. While essential for optimal health, very few foods contain any iodine at all. The typical American diet contains only trace amounts of iodine. This observation was first seen in World War I when large numbers of soldiers developed goiter. Upon investigation, it was found that most of the men with goiter came from regions with iodine-deficient soils. To fill this gap in the average diet, iodine was infused into table salt.

How should supplemental iodine be dosed?

Dosing Lugol’s iodine can be tricky. There are about 2.5 milligrams of iodine in each drop of Lugol’s Solution of Iodine 2%. This is drastically higher than the recommended 150 mcg per day of iodine. Note: one milligram contains 1000 micrograms.

This means that one drop of Lugol’s Solution of Iodine 2% provides a dose nearly 17 times the recommended daily allowance of iodine. Alarmingly, some health “experts” prescribe patients over 20 drops per day! This can result in iodine overdose if taken over weeks, months, or years, which negatively impacts thyroid health. This can stress the liver and cause permanent hormonal damage.

Lugol’s Solution of Iodine 5% contains 6.3 mg of iodine per drop. This equals to 6300 mcg of iodine per drop, or 42 times the RDA of iodine. Iodine supplementation should never be dosed without explicit and specific guidance from an experienced medical provider. This provider should fully understand the effects of iodine dosing, the amounts being recommended, and the consequences and risks of those recommendations. Habitually consuming more than the RDA of iodine can be especially dangerous for patients with Hashimoto’s or Graves diseases.

What are the dangers of iodine overconsumption?

Serious health problems may arise if a person ingests too much iodine. Hypothyroid patients should only take low doses of iodine in the presence of thyroid prescription medication.  Supplemental iodine will increase thyroid activity if ingested alongside thyroid medications. Common symptoms of iodine dysregulation may include:

  • Elevated blood pressure
  • Tachycardia
  • Heart palpitations
  • Anxiety and panic attacks
  • Nausea and vomiting
  • Insomnia
  • Dyspnea

Decoding internet advice

The use of “thyroid supportive” supplements is often touted by nutrition gurus that lack proper education. Videos, blogs, and podcasts meant to “educate” the public may be thinly veiled marketing schemes meant to sell untested and unregulated “cure-alls.” While some people can benefit from some of these “natural” supplements, many vulnerable and at-risk individuals may be harmed by these products.

Remember, natural is not automatically positive. Think of it this way: cyanide is natural, but would you recommend it to your patients? Just because a vitamin or supplement worked for one person, does not mean it is good across the board for people with diverse health needs.

Other “experts” publish information claiming that powdered and ground organ meats in concentrated forms are a magic cure for hypothyroidism. These supplements may work fine for people needing a “little boost” to their energy levels, but taken in excess or in addition to thyroid medicine can put patients’ health in danger. These supplements can also skew the lab values of a patient’s thyroid levels and contribute to treatment-resistant symptoms.

Always be aware of how and where your patients are getting their iodine. Ask specifics about the type of salt they consume. If they don’t know, educate. Encourage them to read iodine supplement labels and fill them in on dosing and serving sizes. Many people believe that if a little is good, a lot is better. That is simply not true –the dose makes the poison.

Get other recommendations on a variety of evidence-based supplements and vitamins while exploring core concepts related to nutritional medicine in Elite NP’s The Functional Vitamin, Supplement, and Nutrition Course.

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