Kelp for Hair: Iodine, the Thyroid & What the Research Shows

Kelp is a seaweed and a concentrated source of iodine. The risk with kelp is too much iodine, not too little: in a study of regular seaweed eaters, iodine status was excessive, and a published case describes thyroid dysfunction after a kelp-containing diet. We found no study of kelp for hair.

Here's what the research shows about kelp, iodine and the thyroid, and how that connects to hair.

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Key Takeaways

• In 44 seaweed consumers in Norway, median urinary iodine was 1,200 μg/L, an excessive iodine status, and the authors advised consumers to be aware of the risk.
• A case report describes a woman with no previous thyroid disease who developed hyperthyroidism followed by hypothyroidism after a kelp-containing diet.
• The recommended daily iodine intake is 150 μg for adults who are not pregnant or lactating.
• We found no study of kelp for hair.

What Is Kelp?

Kelp is a type of seaweed, or macroalga, and a rich source of iodine. It's eaten as food and sold as supplements.

Does Kelp Help Hair?

No study says so. Iodine matters because your thyroid needs it to make thyroid hormones, which also affect hair. See our iodine and hair article. But taking extra iodine from kelp isn't a hair strategy and can backfire.

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Using Kelp Carefully

• Don't megadose. Kelp products can contain very large amounts of iodine, and labels often lack the iodine content.
• Talk to your doctor before taking kelp or iodine supplements, especially if you have thyroid disease.

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What The Research Shows

Seaweed Eaters

In 44 macroalgae consumers in Norway, median urinary iodine concentration was 1,200 μg/L. Seaweed was the major contributor to iodine intake, and labelling of iodine content was lacking for a large share of the products consumed. TSH levels were within reference values but higher than in comparable population groups. The authors concluded that including macroalgae in the diet may give excessive iodine exposure (Aakre et al., 2020).

A Case After A Kelp Diet

A 45-year-old woman with no previous thyroid disease developed signs of hyperthyroidism shortly after starting a marketed diet containing kelp, which lasted 2 months and was followed by overt hypothyroidism. The report suggested iodine-induced thyrotoxicosis from kelp and advised that consumers of diets containing kelp or other iodine-rich ingredients be warned about the risk of thyroid dysfunction (Di Matola et al., 2014). It was a single case.

Iodine Intake

Recommended daily iodine intake is 150 μg in adults who aren't pregnant or lactating. Intakes above that are generally well tolerated, but susceptible people, including those with pre-existing thyroid disease, the elderly, fetuses and neonates, may develop iodine-induced thyroid dysfunction (Leung & Braverman, 2014).

Iodine is the mineral usually discussed with kelp, and our article on iodine and hair looks at it on its own.

See also: Selenium and Hair: What the Research Shows

Frequently Asked Questions

Does kelp help hair growth?

We found no study showing that it does.

Can kelp cause thyroid problems?

Excess iodine from kelp has been linked to thyroid dysfunction in a case report and to excessive iodine status in seaweed consumers.

Is kelp safe?

Talk to your doctor before taking kelp supplements, especially if you have thyroid disease or are pregnant.

References

1. Aakre I, Tveito Evensen L, Kjellevold M, et al. Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway. Nutrients. 2020. PubMed
2. Di Matola T, Zeppa P, Gasperi M, et al. Thyroid dysfunction following a kelp-containing marketed diet. BMJ Case Rep. 2014. PubMed
3. Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol. 2014. PubMed