What is iodine and why is it important?
Iodine is an essential mineral that we typically get from our diets, and it plays a vital role in our hormone balance. Our bodies need iodine to make thyroid hormones that control our metabolism, among other critical functions. The thyroid hormones made possible by iodine also support fetal brain and skeletal development during pregnancy and adolescence, so it is especially important for pregnant mothers and very young children to get enough.
How much iodine do we need?
The US FDA recommends that adults consume a Daily Value (DV) of 150 mcg of iodine. This is a very small amount of iodine, but critical to your health nonetheless. In the US, the median intake of iodine is about 240 - 300 mcg per day for men and 190 - 210 mcg for women. As with most essential nutrients, too little can cause health problems, but too much can also cause health problems; it's all about proper balance. The maximum amount you can take without a potential negative impact on your health is 1,100 mcg per day (7.3 times more than the recommended DV), also known as The Tolerable Upper Intake Level (UL). While adequate levels of iodine support thyroid and hormone health, too much may disrupt thyroid function, leading to hypo- or hyperthyroidism, and weight gain. It is very uncommon for people to consume more than the UL. Iodine deficiency is more common.
Iodine deficiency, symptoms, and health consequences
According to The Lancet medical journal, a large study on iodine intake showed more than 1.9 billion people have inadequate iodine intake on a global basis. The highest prevalence is found in Europe, where 59.9% tested with inadequate iodine levels. The lowest prevalence is in the USA, where 10.1% tested deficient. These study findings prove that iodine deficiency is still a public health issue worldwide.
Symptoms of iodine deficiency are wide-ranging, including:
- Weight gain
- Weaker immune system
- Feeling cold all the time
- Dry and cracked skin
- Enlarged thyroid gland (goiter)
Health consequences of iodine deficiency are most severe for developing fetuses and very young children. In extreme cases, fetal brain and skeletal development can be impaired if the mother is extremely deficient. Very young children can also experience the same issues if their diets do not include enough iodine.
Why are vegans more prone to iodine deficiency?
The major sources of iodine in the American diet include dairy products and seafood. Vegan sources of iodine are less abundant compared to animal sources of iodine, and for that reason, vegans are more prone to iodine deficiency. In 2016, an Oxford study of 18,244 meat-eaters, 4,531 fish-eaters, 6,673 vegetarians and 803 vegans showed that vegans were falling short of iodine. Another published study assessed the diets of 81 adults, finding 80% of vegans and 25% of vegetarians were iodine deficient versus only 9% of people on diets that included animal sources.
The best vegan iodine sources from plant-based food
Fortunately, there are potent vegan iodine sources. The iodine-rich foods vegan experts recommend include seaweed and iodized salt, which can easily be added to any vegan diet. If you don't like seaweed, it is very easy to sprinkle iodized salt on your meals, so there is no excuse for being deficient in this mineral. But note: the concentration of iodine in seaweed is extremely variable, and can be very high (see table below), so avoid this food if you have a thyroid problem, and seek the advice of a physician. Some health organizations advise limiting seaweed to one serving per week during pregnancy because if it contains too much iodine, it could disrupt thyroid function. Other plant food sources that contain iodine, although at lower concentrations, are listed in the table below:
Vegan Iodine Source
Iodized salt (1.5 g, ~1/4 tsp)
Seaweed, whole or sheet, 1 g
16 to 2,984 mcg
11% to 1,989%
Enriched white bread, 2 pc
Dried prunes ( 5 prunes)
Lima beans (mature), boiled, 1/2 cup
Banana (1 medium)
Other iodine-rich foods vegans should seek out include green beans, kale, organic potatoes with skin, spring greens, zucchini, watercress, and strawberries.
Although vegan sources of iodine are available, for those of us who don't want to spend the effort planning for adequate iodine intake, or who eat out often and don't want to carry around a bottle of iodized salt, then it may be difficult to meet our daily requirement through food alone. For this reason, we should consider a vegan iodine supplement.
Vegan iodine supplements: Should you take them? Which are best?
If you opt for a vegan iodine supplement, which is a good choice for many vegans, then don't use one that contains more than the DV of 150 mcg of iodine. You will get some iodine from your diet, so when you add that diet-sourced amount to the 150 mcg from the supplement; it should be sufficient to keep you healthy without risking too much intake.
You can take a supplement with iodine only, but I recommend that my vegan patients take a vegan multivitamin with 150 mcg of iodine because other nutrients work synergistically with iodine, like selenium. I also recommend taking iodine in a multivitamin because there are many other nutrients vegans need, like vitamin B12 (which must be supplemented by vegans), omega 3-6-9, iron, choline and zinc. Instead of a pill vitamin, I recommend a new MICROGEL™ supplement by Healthycell made specifically for vegans to fill the gaps in plant-based diets, called Vegan Essentials.
To your health,
Dr. Vincent Giampapa, MD, FACS
Visiting Scholar, The Sinclair Lab
Harvard University, Boston, MA
Cell Aging Researcher & Author
Director, Cell Health Institute