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The Evidence

Page 07

Iodine on a vegan diet

Iodine is the quiet one: no drama, easy to miss, easy to fix. Iodized salt or a measured amount of seaweed does it, and kelp can overshoot hard.

Vegan Brief Evidence last reviewed July 6, 2026

This is a summary of the cited evidence, not medical advice.

  • RDA (adults) 150 mcg/day
  • Simplest source Iodized salt
  • Watch out Kelp can overshoot

The short version

Iodine rarely comes up, which is exactly why it is worth a page. In many countries the main dietary sources are dairy and seafood, so a vegan who also uses non-iodized salt can quietly run low. The fact sheet names the groups at risk.

Primary source 01 / 03

Vegans, people with certain food allergies or lactose intolerance, and others who consume no or minimal amounts of these foods might not obtain sufficient amounts of iodine [49,50].

NIH Office of Dietary Supplements US National Institutes of Health Iodine: Fact Sheet for Health Professionals, 2024

The stakes are real: sustained shortfall enlarges the thyroid.

Primary source 02 / 03

In the absence of sufficient iodine, TSH levels remain elevated, leading to goiter, an enlargement of the thyroid gland that reflects the body’s attempt to trap more iodine from the circulation and produce thyroid hormones.

NIH Office of Dietary Supplements US National Institutes of Health Iodine: Fact Sheet for Health Professionals, 2024

Getting it right without overshooting

Two vegan routes work, with one caution. Iodized salt is the easy, boring, effective answer. Seaweed is the other, and it is potent.

Primary source 03 / 03

Seaweed (such as kelp, nori, kombu, and wakame) is one of the best food sources of iodine [5].

NIH Office of Dietary Supplements US National Institutes of Health Iodine: Fact Sheet for Health Professionals, 2024

The caution is that kelp can carry so much iodine that a single serving blows past the daily target many times over, and too much iodine causes its own thyroid problems. Nori sheets are gentler. The reliable move is iodized salt, or a supplement with a known dose, rather than guessing with kelp.

  • Vitamin D on a vegan diet Vitamin D is the one almost everyone runs low on in winter, vegan or not. The plant-friendly fix is D2 or lichen D3, plus fortified foods and sensible sun.
  • Vegan diets in pregnancy and childhood This is the page to get right, so it is the page with the most hedging. The dietitians' body says a planned vegan diet works at every life stage. The same sources say B12 is not optional.
  • Selenium on a vegan diet Selenium is the mineral your food inherits from the dirt it grew in. That makes plant levels a lottery of geography, and it is why vegan intakes can run low, and why two Brazil nuts can flip the whole thing.

Frequently asked

Do vegans need an iodine supplement?

Not necessarily. Iodized salt or a measured amount of nori usually covers the 150 mcg adult target. A supplement is a reliable alternative if you avoid iodized salt.

Is seaweed a good iodine source for vegans?

Yes, but amounts vary enormously. Kelp can massively overshoot the safe intake; nori is more moderate. Iodized salt is the more predictable source.

The primary sources

The documents this page quotes. Read them yourself.

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