Iodine functions in the body as a building block for thyroid hormones1. Through the thyroid hormones, iodine affects normal growth and development, particularly in the central nervous system. Thyroid hormones also play a role in basal metabolism as well as adjustment to prolonged stress. Both excessive and insufficient intake of iodine over a prolonged period cause impairments to thyroid function, which is why ensuring appropriate intake of iodine is important. In Finland, the amount of iodine in the soil is poor, and therefore iodine is added into table salt and animal fodder.
The vegan diet contains fewer sources of iodine than an omnivorous diet. For this reason, the Finnish recommendation is that all vegans use a dietary supplement containing iodine2, 3. However, children below school age can meet their iodine needs by consuming large enough amounts of iodine-fortified plant milks. Young children may even exceed the upper limit for safe intake if they also use an iodine supplement and iodized salt in addition to fortified plant milks. Read more about planning a safe vegan diet for kids and iodine intake here.
Where do vegans get iodine?
Sources of iodine in the vegan diet include iodized salt, iodine-fortified plant milks, yogurts and quarks as well as seaweed4. Many special salts such as sea salt and Himalayan salt do not naturally contain iodine in nutritionally significant quantities. However, iodized versions of these salts are also available. In 2015, The National Nutrition Council of Finland gave a recommendation for increasing the use of iodized salt in the food industry2. After this, the use of iodized salt has become more common in products such as bread and ready meals.
Click this link to see the iodine contents of different plant-based milks.
Table 1. Iodine contents of certain food products per gram.
| Product | Iodine content, μg per g |
| Seaweed, kombu, dried | 4290 |
| Kelp powder | 650 |
| Seaweed, wakame, dried | 152 |
| Table salt, iodized | 25 |
| Seaweed, nori, dried | 21 |
| Sea salt, non-iodized | 0,74 |
| Iodized oat milk | 0,16 – 0,225 (16 – 22,5 μg per 100g) |
| Iodized plant-based yogurts, e.g. Oddlygood brand | 0,225 (22,5 μg per 100g) |
Problematic seaweed
Though ostensibly a good source of iodine, there are several problems with using seaweed. Determining the iodine contents of seaweed is difficult, because the amount of iodine in seaweed varies greatly. Factors such as geographic habitat, sea depth, saline levels of sea water, storage conditions as well as food preparation methods affect the final iodine contents of seaweed5. On these grounds, it is understandable that in Finland, it is recommended that infants do not consume seaweed6. Children between the ages of 1 and 6, as well as pregnant and breastfeeding adults, should not consume seaweed if the iodine content is unknown or known to be high. Some seaweed has also been found to contain high levels of heavy metals6.
How to get enough iodine?
Adequate iodine intake on a vegan diet can be reached either by using a supplement or consuming iodized food products. The easiest and most reliable way is to use a supplement that contains iodine, as many supplements contain the recommended daily amount for adults. Alternatively, iodine needs can be met by consuming iodine-fortified plant milks and yogurts as well as iodized salt, as long as they are consumed regularly and in sufficient quantities. For example, 4 grams of iodized salt (100 μg of iodine in total) plus a little over 2 deciliters of iodine-fortified oat milk that contains 22,5 μg of iodine per 100 ml (50 μg of iodine in total) would be enough to meet the recommended daily intake for adults and children over the age of 10, which is 150 μg. However, not all plant milks are fortified with iodine.
Because the maximum recommended daily intake for table salt is five grams, the recommended amount of iodine cannot be obtained just from iodized salt. Seaweed can also be used as a source of iodine if the exact iodine content of the seaweed is known and as long as total iodine intake from food and supplements does not exceed 600 μg per day in adults.2, 6 Kombu seaweed as well as kelp powder contain such high levels of iodine that safe dosage cannot be guaranteed. Iodine is absorbed more or less completely, which is why extra care must be taken not to exceed the upper limit for safe intake. In studies, iodine intake and the body’s iodine levels have often been suboptimal in vegans, including in Finland7.
Children below school age can meet their iodine needs without a supplement by consuming iodine-fortified plant milks and yogurts. For example, 5 deciliters of iodized oat milk provide between 80 and 113 μg of iodine. The upper limits for safe iodine intake are lower for children than for adults (Table 2). Children may exceed the upper limit for safe intake if they use an iodine supplement and simultaneously consume large amounts of iodized plant milk products. For this reason, we do not recommend an iodine supplement for children below school age who consume at least 5 deciliters of iodized plant milk products daily.
Iodine supplements suitable for vegans
There are a few supplements on the market which contain iodine and are suitable for the vegan diet. Typically, these products contain 150 μg of iodine, which is the daily recommended intake for adults3. The upper limit for safe iodine intake for adults is 600 μg, and this should not be exceeded for an extended period of time3. Iodine tablets sold in pharmacies for the event of a radiation accident cannot be used as dietary supplements. They contain more than 50 times the upper limit for safe iodine intake.
Iodine supplements suitable for the vegan diet include:
- Multivita Vegan multivitamin (150 µg)
- Solgar Kelp (200 µg)
- VEG1 (150 µg)
- Vegetology MultiVit (150 µg)
- Vitatabs Jodi (150 µg)
- Vitaali Jodi (150 µg)
- Sana-sol vegaani multivitamin (150 µg)
Supplement products aimed at pregnant and breastfeeding people, such as Terranova Prenatal (100 µg) do not usually contain enough iodine for the needs of those pregnant or breastfeeding, which is why iodine intake must be supplemented with other sources.
Table 2. Adequate iodine intake as well as upper limit for safe iodine intake for different age groups.3, 8
| Age | Adequate daily intake | Upper limit for safe daily intake |
| ≤ 6 m* | 80-90** μg | not defined |
| 7-11 m | 80-90** μg | not defined |
| 1-3 y | 100 μg | 200 μg |
| 4-6 y | 100 μg | 250 μg |
| 7-10 y | 100 μg | 300 μg |
| Women | ||
| 11-17 y | 120 μg | 11-14 y: 450 μg; 15-17 y: 500 μg |
| ≥ 18 y | 150 μg | 600 μg |
| Pregnant people | 200 μg | 600 μg |
| Breastfeeding people | 200 μg | 600 μg |
| Men | ||
| 11-14 y | 130 | 450 μg |
| 15-17 y | 140 | 500 μg |
| ≥ 18 y | 150 | 600 μg |
*Exclusive breastfeeding is recommended for infants between 0 and 6 months of age. The values for infants below the age of 6 months are based on estimated intake from breast milk and represent sufficient intake3.
**Adequate intake for iodine for infants below the age of 12 months is presented as a range: 80 μg of iodine per day for populations with adequate iodine intake, and 90 μg of iodine per day for populations with mild to moderate iodine deficiency3.