Iodine is an often overlooked, yet essential, mineral. It may be a concern on a vegan diet, depending on the food choices made.
- What is Iodine?
- What Does Iodine Do in the Body?
- Daily Intake Requirements of Iodine
- Iodine Deficiency
- Iodine Toxicity
- How to Consume Enough Iodine as a Vegan
- Vegan Food Sources of Iodine
- Iodine Supplements for Vegans
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What is Iodine?
Iodine is an essential mineral meaning the body requires iodine but cannot produce any iodine itself. Therefore, iodine, like any essential nutrient, must be consumed through the diet.
Iodine is one of the more common nutrient deficiencies in developing countries. With the introduction of iodized salt, iodine intake in Canada is generally at adequate levels. The other major sources of iodine are dairy products and seafood.
Since vegans don’t consume dairy or seafood, and people are generally encouraged to limit salt intake, getting enough iodine on a vegan diet can become a challenging 1.
What Does Iodine Do in the Body?
Iodine is essential because it's needed to make thyroid hormones.
Thyroid hormones control the body's metabolism and are also used for proper development of the brain and bones. A lack of thyroid hormone can lead to hypothyroidism and other health concerns.
Iodine is particularly important for pregnant mothers and infants/ children due to it's critical role in growth and development.
Daily Intake Requirements of Iodine
For men and women age 19 and over, the recommended dietary intake is 150 ug (micrograms) per day. Pregnant and lactating women have different intake needs 3. There’s no evidence to suggest vegans need higher iodine intakes compared to the general population. Therefore, vegans should aim to meet the iodine intake needs outlined above (which are sourced from Health Canada).
Due to concerns of excessive iodine intake, there is also a tolerable upper limit set for this nutrient. For men and women aged over 19, the upper intake limit is 1100 ug (micrograms) per day 3. Intakes up to this level should be safe; however, intakes above this level may have adverse effects and are not recommended (unless otherwise instructed by a medical practitioner).
In adults, iodine deficiency can lead to low levels of thyroid hormones which cause hypothyroidism 1. Over time, this can lead to an enlarged thyroid, called a goiter. Other symptoms of iodine deficiency can include weakness, fatigue, intolerance to cold and weight gain.
In pregnancy, a mother’s limited intake of iodine can cause cretinism. Cretinism can present as a mental and physical disability and can result in stunted growth, low IQ, deafness and/or muteness.
If you have any of the symptoms above please go see a doctor. If you are concerned about your intake of iodine, speak to your doctor as soon as possible.
While iodine deficiency is a major concern, it’s also possible to take in too much iodine which can have toxic effects. Iodine toxicity has been reported in case studies, often in people who have an underlying condition such as a thyroid disease or in infants or the elderly 2.
Iodine toxicity can occur after a single large dose of iodine, or with chronic high levels of exposure 2. The effects of iodine toxicity could be transient (a person recovers from the toxic levels) or permanent 2. Permanent effects from iodine toxicity are typically related to impaired thyroid function, which could lead to either hypothyroidism (low levels of thyroid hormones) or hyperthyroidism (high levels of thyroid hormones) 2.
How to Consume Enough Iodine as a Vegan
On a vegan diet there are two main sources of iodine: iodized salt and seaweed. A half teaspoon of iodized salt per day is enough to meet intake recommendations for non-pregnant adults. This amount of salt provides about 1000 mg of sodium. Sodium intake recommendations vary, however many health organizations target an intake of sodium of less than 1500 mg per day 4.
Seaweed is not a reliable source of iodine as there is no way to know how much iodine is present in the seaweed. In addition, there may be concern for seaweed and seaweed products to contain high-levels of iodine that may be harmful.
Some people may benefit from limiting their salt intake. If you fall into this category, speak to a doctor or dietitian about how to best meet your iodine intake requirements.
Vegan Food Sources of Iodine
The most reliable source of iodine on a vegan diet is iodized salt. I generally recommend that if you consume salt, choose an iodized salt. Specialty salts (ex. pink Himalayan, sea salt, Kosher salt etc.) are often not iodized and therefore contain very low levels of iodine. There are brands that iodize sea salt, if that's of interest to you.
Seaweed is a potential source of vegan iodine, however there are concerns with excess iodine from seaweed, and excess iodine and arsenic with seaweed tablets 1. It’s best to speak with your doctor before deciding to increase the amount of seaweed in your diet.
Bread products can be a source of iodine on a vegan diet; however, the levels are lower than what is needed to meet daily recommendations.
Fruits and vegetables aren’t a reliable source of iodine on a vegan diet. They cannot be relied upon due to the variation in iodine content of soil. You get some iodine from fruits and vegetables, but it’s likely not enough to meet the daily requirements for this nutrient.
Iodine Supplements for Vegans
If you don’t consume iodized salt and/ or seaweed on a regular basis, speak with your doctor about an iodine supplement. Iodine supplementation isn’t necessary if you meet intake needs through food sources (iodized salt).
The concern is that it’s difficult to measure how much iodine you get from food sources alone. Only iodized salt has levels of iodine that are reliable, therefore if you use other sources of iodine and are concerned about your intake, a supplement may be useful. Always speak with your doctor before starting any new supplements.
Iodine supplements can be made from a range of sources. Iodine supplements prepared from seaweed (ex. kelp tablets) might not be the best idea due to possible arsenic contamination 1.
Potassium iodine supplements that aren’t made from kelp could be the best option 1. It’s likely that supplementing up to the daily intake recommendations are a good target; however it’s essential to speak with your doctor before starting any new supplements.
Summary: Iodine for Vegans
Iodine is an essential mineral used to create thyroid hormones. Deficiency and toxicity are both possible so care needs to be taken to ensure adequate amounts are consumed, but excess amounts are not taken. Iodized salt is the most reliable way to ensure adequate intake of iodine on a vegan diet. If you need to limit your salt intake, or are otherwise concerned about your intake of iodine, speak to a Registered Dietitian. Iodine supplements may be helpful but always speak to a doctor before starting/ stopping any supplements.
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Author Profile: Nicole Stevens
Nicole is a vegan Registered Dietitian (RD) and founder of Lettuce Veg Out. She provides vegans with balanced meals and easy-to-understand nutrition science.
Having attained a Masters degree and passing a national registration exam, Nicole is a trusted source of nutrition information. She uses this knowledge to educate others about vegan diets and how to thrive as a vegan.