What about iodine on a vegan diet?

The objection

“Iodine comes from dairy and seafood. Vegans are setting themselves up for thyroid problems.”

The answer

The objection lands a real hit here, and pretending otherwise would undermine everything else on this site. Iodine is a genuine weak spot of unplanned vegan diets.

The evidence is clear. A systematic review across diet groups found vegans tend to have the lowest iodine intake and the lowest urinary iodine (the standard marker of status), frequently below adequacy. In countries that don’t iodise salt or fortify widely, vegans and vegetarians show measurable deficiency risk. Dairy and seafood genuinely are the main iodine sources in many Western diets, so removing them without a plan leaves a gap. Iodine matters: it’s essential for thyroid hormones, and deficiency in pregnancy harms fetal brain development.

But “needs planning” is a long way from “impossible,” and the fix doesn’t involve animals. Iodised salt is the cheapest, most reliable global solution, and a small amount covers requirements. A measured iodine or kelp supplement providing around the 150 µg adult target works too.

The one thing not to do is wing it with seaweed. Seaweed iodine content is wildly variable. Some kelp delivers a dangerous excess in a single serving, which can disrupt the thyroid as badly as deficiency. So the advice is a known, measured dose, not “eat lots of sea vegetables and hope.”

So the defensible position is straightforward. Iodine is the strongest nutritional argument for planning a vegan diet rather than drifting into one. Planned, it’s a non-issue. Ignored, it’s a real risk, and saying so plainly is the honest thing to do.