Sea moss side effects

No published trial has tested this combination, so side-effect rates for sea moss with bladderwrack are unknown. The documented concerns are about iodine: seaweed products vary widely in it, and case reports link kelp and bladderwrack products with temporary thyroid overactivity. Other cautions are trace metals, burdock allergy and a hormonal signal from bladderwrack.

What is known and unknown about sea moss side effects

We found no human safety trial of whole Irish moss, and none of the Irish moss, bladderwrack, burdock and black pepper extract combination in Electric Tiger Sea Moss with Bladderwrack + Burdock. That means we cannot tell you how often any side effect happens. What exists are laboratory measurements of seaweed and individual case reports, summarised below. Case reports show that something can happen; they cannot show how likely it is.

Iodine and the thyroid

All seaweed contains iodine, and the amount varies enormously. A 2004 analysis of 12 commercial seaweeds found 16 mcg per gram in nori and over 8,165 mcg per gram in a processed kelp sample, and up to about 13-fold differences within one kelp species depending on harvest conditions (PMID 15588380). In 2021, a lab survey of 96 seaweed products found iodine per daily dose of supplements ranging from 5 to 5,600 mcg, with labels for species and iodine often inadequate or inaccurate (PMID 33889064). Irish moss is at the low end: 30 dried samples averaged 3.86 mcg per gram (PMID 32803579). Bladderwrack is the variable one in a blend.

The adult recommended dietary allowance is 150 mcg a day and the tolerable upper level is 1,100 mcg; the American Thyroid Association advises against iodine and kelp supplements delivering more than 500 mcg a day, and notes that older adults, people who are pregnant or lactating and people with existing thyroid disease are more susceptible to excess (ATA statement). Our panel does not state an iodine amount, and it varies by batch.

The reported harms are case reports. A 70-year-old woman with no thyroid history developed a fast heart rate, insomnia, anxiety and weight loss with transient hyperthyroidism about three months after starting kelp tablets, which resolved after she stopped them and took antithyroid medicine for three months (PMID 31517826). A 1998 case report is titled "Transient hyperthyroidism in a patient taking dietary supplements containing kelp" (PMID 9876004), and a 60-year-old man taking lithium developed hyperthyroidism on a herbal preparation containing bladderwrack that remitted when it was withdrawn (PMID 22127913). Kelp is far richer in iodine than Irish moss, and these reports do not show that our capsules would do this; they show why the iodine total matters. Stop taking a seaweed supplement and see a doctor if you notice a racing heart or unexplained weight change.

Trace metals

Seaweed can contain trace metals from the water it grows in. In 14 edible seaweeds, total arsenic reached 67.6, cadmium 7.2 and lead 6.7 mg/kg dry weight, varying by species; the authors judged the seaweeds tested not to be a threat but said the elements should be controlled (PMID 26817952). That analysis did not break out bladderwrack. "Organic" on a label does not address metals in seawater. The label does not claim metals testing, and no certificate of analysis for metals is on file for this product.

Burdock allergy

Burdock is a daisy-family (Asteraceae) plant. A case report describes an allergic skin reaction to burdock applied to skin (PMID 8549139). It was topical rather than swallowed, and we found no data on oral cross-reactivity, so we word it as a precaution: if you are allergic to daisy-family plants, ask a physician first.

Hormonal effects of bladderwrack

In three pre-menopausal women with abnormal cycles or related disease histories, 700 mg to 1.4 g a day of bladderwrack was followed by cycles 5.5 to 14 days longer, and hormone changes in the one woman measured; there was no control group and the author called it pilot data (PMID 15294021). It is thin evidence, but it is a reason for people with hormone-sensitive conditions to ask first.

Questions people ask

What are the risks of sea moss?

Iodine excess affecting the thyroid, trace metals, allergy to a daisy-family plant and hormonal effects are the ones with documented reports. Rates are unknown.

Do the capsules cause stomach upset?

We found no data on digestive side effects of this combination, so we cannot give a rate. Stop if anything bothers you.

How do I lower the risk?

Take the label amount once a day, not more. Add up iodine from other seaweed, kelp, multivitamins and iodised salt, and ask a doctor first if any group in who should not take sea moss describes you. Medicines are covered in sea moss and medications.