Iodine on a Vegan Diet – Sources, Deficiency, Absorption, Supplements
February 28, 2022
Getting enough iodine on a vegan diet is important. Iodine is an ‘essential mineral’, meaning that our body cannot make it and it has to be consumed from the diet. It is important for thyroid function as it supports the production of vital thyroid hormones, which have several functions (1,2):
- Controlling our metabolism
- Producing cells
- Balancing hormones
- Heart, muscle and digestive system function
- Central nervous system and bone development for infants and foetuses
- Intellectual function for children
Iodine requirements on a vegan diet
Requirements are the same for those following a vegan diet as they are for non-vegans. Groups that have the highest requirements include women who are pregnant or breastfeeding/lactating.
Best food sources of iodine
Iodine is most easily found within animal foods such as seafood, eggs and meat, meaning that it can be a bit more difficult to get enough on a vegan diet. Plant foods that contain iodine include seaweed, kelp and some fruits and vegetables.
However, it is difficult to predict iodine content as it can be highly variable. In Australia, most soil is iodine-poor which reduces the mineral content in these foods.
The two main sources of iodine for vegans are seaweed and iodised salt. It is not recommended to rely on seaweed for adequate intake of this mineral because seaweed can be highly variable and in some cases, too high which can risk iodine toxicity. Seaweed is also at risk of heavy metal contamination (3). The safest seaweeds appear to be nori and wakame as they have been found to have the lowest iodine content (4).
Iodised salt is fortified with iodine and can help to meet needs on a vegan diet (5). In Australia, iodised salt contains 25–65 micrograms of iodine per gram of salt. This means that ½ teaspoon of iodised salt provides about 50-120% of iodine requirements (for the general population) across the day. It is also legally required that bakers use iodised salt in bread products (6).
Be mindful that specialty salts (Himalayan, sea salt) are usually not fortified with iodine. If you are currently using these, consider swapping over to an iodised salt.
Meeting iodine needs: day on a plate
Breakfast: 2 slices seeded bread/toast (not organic) + ½ a med avocado + ½ med tomato + 30g hemp seeds + squeeze of lemon juice
Lunch: Wholegrain wrap with 1 cup salad vegetables, ¼ cup hummus and 100g tofu (baked/pan fried with olive oil + 1/8 tsp iodised salt)
Dinner: Mediterranean chickpea & vegetable fettuccine (with 2 cups mixed vegetables roasted with ¼ tsp iodised salt)
Snacks: 1 med banana + ¼ cup plant-based yoghurt + 30g almonds
Iodised salt and high blood pressure risk
Consuming too much sodium (from salt) is linked to health conditions such as hypertension (high blood pressure), heart failure and renal (kidney) disease.
On a balanced and healthy diet, guidelines in Australia recommend limiting sodium intake to 2000mg per day. It is important to still include some sodium in the diet as it has a range of functions including maintenance of blood plasma and cell production (6).
Consuming ½ teaspoon of iodised salt provides ~1000mg sodium with 70-170μg of iodine. This will likely meet the 150mcg daily requirement for a non-pregnant or breastfeeding adult when some salt is included in cooking and combined with fortified bread products.
While monitoring sodium levels is important, choosing iodised salt will help vegans to reach sufficient iodine intake.
Maximising iodine absorption
While consuming enough iodine is important, it’s also important to understand that some foods contain chemical components that can reduce the uptake of iodine into our bodies (1). Goitrogens are a type of compound found in some raw green leafy vegetables that can interfere with the synthesis of thyroid hormones by impairing the binding of iodine.
Sweet potato and corn contain chemicals that compete for the same receptors as iodide (which is iodine when bonded to another element), which can block uptake by the thyroid (1).
Examples of foods that inhibit iodine absorption include:
- Soy foods
- Raw cruciferous vegetables (cabbage, broccoli, brussel sprouts)
- Sweet potato
- Corn/maize products
Is being vegan a risk factor for developing an iodine deficiency?
There are several populations, including vegans, who are at risk of developing an iodine deficiency. Iodine deficiency has been a global concern for over 100 years.
In the 1920’s, iodised salt was introduced as a way to increase the population’s iodine intake. In the early 2000’s, national studies showed that Australians were still not getting enough iodine, regardless of following a vegan diet or not.
Food Standards Australia and New Zealand (FSANZ) made a decision that from 2009, all bread on the market (with the exception of organic bread) was to use iodised salt as their bread conditioner (2,3) to help boost iodine levels nationwide.
Signs of an iodine deficiency
Mild iodine deficiency is somewhat prevalent in Australia, and severe deficiency (intake below 50μg/day) can lead to conditions such as hypothyroidism. This condition results from the thyroid not producing enough thyroid hormones, slowing down the function of the gland.
Symptoms of hypothyroidism include:
- Dry skin
- Hair loss
- Increased sensitivity to the cold
- Weight gain
- Decreased fertility rate
- Muscle weakness and stiffness
Very severe iodine deficiency (below 30μg/day) during pregnancy can lead to a condition called cretinism in infants and children. This can have significant impacts as it can affect their development physically and mentally with an increased risk of intellectual disability (1,2).
Should I supplement iodine as a vegan?
It is definitely attainable to consume enough iodine on a vegan diet, however there may be some instances where a supplement may assist. If you rarely consume seaweed, have to limit salt intake and/or do not eat fortified bread products, it may be wise to supplement iodine individually or as part of a multivitamin.
For pregnant or lactating mothers, requirements are highest and supplementation will likely be necessary. However, before starting iodine supplements, it’s best to speak to your GP or dietitian.
Our dietitian team at Plant Nutrition and Wellness are experts in vegan and plant-based nutrition and can provide guidance on meeting iodine requirements. If you are wanting to make sure that you are meeting nutrient needs on a vegan diet, book a free discovery call today.
This blog was co-written by PNW Clinic dietitian Megan Boswell and student dietitian Leanna Fyffe.