Sea moss and your thyroid: an honest guide to iodine

Search "sea moss" and "thyroid" together and you'll find a lot of confident promises. We're not going to add to them. Belo makes food, not medicine, so we can't and won't tell you sea moss treats, prevents or manages any thyroid condition — and you should be sceptical of anyone who does.

What we can do is explain, plainly, why iodine matters to the thyroid in general, what the iodine numbers on our own gel actually mean, and exactly who should talk to a clinician before adding sea moss to their routine. That's the honest version, and it's the one worth reading.

This is general information, not medical advice. It is not a substitute for guidance from your own doctor or an accredited practising dietitian.

Why iodine matters to the thyroid (the general biology)

This is textbook physiology, not a claim about our product. Your thyroid, a small gland at the front of your neck, uses iodine as a raw material to make thyroid hormones. Those hormones help regulate metabolism across the body. Because the human body can't make iodine, it has to come from the diet — which is why iodine is classed as an essential nutrient.

Australia and New Zealand set reference intakes for it. The adult Recommended Dietary Intake (RDI) is 150 µg of iodine a day, rising for pregnancy and breastfeeding, with an Upper Level of Intake of 1,100 µg a day for adults (NHMRC Nutrient Reference Values). Australian soils are naturally low in iodine, which is part of why iodine deficiency re-emerged here and why iodised salt is now added to most bread (FSANZ). Seaweed is one of the few foods that is naturally high in iodine — sometimes very high.

That last point cuts both ways, and it's the reason this guide exists.

What the numbers on our sea moss actually mean

We measured the iodine in our finished gels rather than guessing. Tested as eaten, they came in at 0.66 mg/kg (Soothing Honey Lemon & Matcha) and 1.1 mg/kg (Classic Lime) — which works out to about 10–17 µg per 15 g serve, or roughly 20–33 µg per two-tablespoon daily amount. The full reports, and the toxicological assessment by the Western Australian Department of Health (2026), are on our lab results page.

Set that against the 150 µg RDI and the 1,100 µg upper level and you can see the shape of it: a daily serve is a modest, supportive contribution toward iodine intake at recommended use, sitting well below the upper limit for the general population. It is not a high-dose iodine supplement, and we don't position it as one.

One honest caveat: iodine in seaweed varies with species, growing conditions and processing. A 2024 study measured total iodine across edible seaweeds ranging from 52 to over 1,300 mg/kg dry weight, with the fraction the body can absorb varying widely too (Zhou et al., 2024); a systematic review of brown algae found much the same species-and-processing variability (Blikra et al., 2022). Our figures are for the batches we tested, on the species we use — Kappaphycus alvarezii ("Eucheuma cottonii", gold sea moss), a warm-water red seaweed that carries far less iodine than high-iodine brown kelps. We retest and republish rather than quoting one number forever.

Why more iodine is not automatically better

It's tempting to assume that if iodine feeds the thyroid, more iodine must be better for it. That's not how the nutrient works. Iodine has a "just right" band: both too little and too much can disturb normal thyroid function, which is exactly why health authorities set an upper level as well as a recommended one. This is general nutrition science — again, not a claim about our gel — but it's the single most important idea for anyone thinking about sea moss and thyroid health. The goal is adequacy, not maximisation.

That's also why we print "do not exceed the recommended amount" and mean it. Stacking sea moss on top of iodine supplements, kelp tablets, or a diet already heavy in seaweed can add up faster than people expect.

Exactly who should check with a clinician first — and who should not use it at all

Here is the suitability statement we put wherever iodine comes up, word for word:

Sea moss is naturally rich in iodine. This product is not appropriate for individuals with hyperthyroidism. Do not exceed the recommended amount. Consult a healthcare professional before use if you are pregnant, taking medication, or have a thyroid condition.

Breaking that down:

• If you have hyperthyroidism (an overactive thyroid), sea moss is not appropriate for you. That's not a hedge — it's a clear "this isn't your product". Extra iodine is not something an overactive thyroid needs.
• If you're pregnant or breastfeeding, your iodine needs are higher and more tightly balanced, and iodine crosses to your baby. Talk to your clinician or midwife before adding any new iodine source.
• If you take medication — thyroid medication especially, but not only — check for interactions with a professional first.
• If you have any diagnosed thyroid condition (Hashimoto's, hypothyroidism, nodules, a history of thyroid treatment), your situation is individual. The right call comes from someone who can see your bloods and your history, not from a blog or a label.

If none of those apply to you and you're a generally healthy adult, sea moss can be part of a varied diet at the recommended amount, like any other iodine-containing food. If you're not sure which group you're in, that uncertainty is itself a good reason to ask.

What good, honest information looks like

You deserve a simple test for any sea-moss-and-thyroid content you read, including ours:

1. Does it avoid disease claims? No food should promise to treat, cure, balance or fix your thyroid.
2. Does it give real iodine numbers, per serve, with a lab report behind them? Vague "rich in iodine" isn't enough to judge.
3. Does it name who shouldn't use it? Honest iodine information always includes the hyperthyroidism caution.
4. Does it send you to a clinician for anything medical? Because that's where thyroid decisions belong.

We've tried to hold ourselves to that. Our per-serve iodine, arsenic and heavy-metal panels, and microbiology are all published in full at trybelo.com/pages/lab-results, and if you want to see the product itself, here's our Classic Lime sea moss gel. Sea moss can be good for your belly — but when it comes to your thyroid, the best thing we can offer is straight facts and a nudge to talk to someone who knows your health.

References

1. National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand — Iodine. https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/iodine
2. Food Standards Australia New Zealand. Iodine in food and iodine requirements. https://www.foodstandards.gov.au/consumer/nutrition/iodine-sensitivities/iodinefood
3. Food Standards Australia New Zealand. Iodine fortification. https://www.foodstandards.gov.au/consumer/food-fortification/iodine-fortification
4. Zhou S, Zhang D, Kong Y, Zhang Q, Cui X. In Vivo Bioavailability and In Vitro Bioaccessibility of Iodine in Edible Seaweeds: Method Development and Health Implications. Environmental Science & Technology. 2024;58(51):22553–22562. doi:10.1021/acs.est.4c08990
5. Blikra MJ, Henjum S, Aakre I, et al. Iodine from brown algae in human nutrition, with an emphasis on bioaccessibility, bioavailability, chemistry, and effects of processing: A systematic review. Comprehensive Reviews in Food Science and Food Safety. 2022;21(2):1517–1536. doi:10.1111/1541-4337.12918
6. Australian Bureau of Statistics. Australian Health Survey: urinary iodine (4364.0.55.006). https://www.abs.gov.au/ausstats/abs@.nsf/mf/4364.0.55.006