Iodine, Explained: What to Know About Sea Plants and Your Thyroid

If you read supplement labels closely, you have probably paused at the word iodine, especially if the product contains sea moss. That pause is reasonable, and we would rather meet it with numbers than with reassurance. This post covers what iodine does, why seaweed is such an unpredictable source, and how we approach it in the Tide Line.

A safety note first

Formulas that contain Wild Purple Sea Moss and bladderwrack provide naturally occurring iodine and are not recommended for those diagnosed with hyperthyroidism. If you have a thyroid condition, or you take thyroid medication, talk with a clinician before adding any new supplement, including ours. Nothing in this post is medical advice, and no supplement can or should claim to address a thyroid condition.

Why this comes up at midlife

Many women start paying closer attention to thyroid health in the years around menopause. The American Thyroid Association estimates that about 1 in 8 women will develop a thyroid condition in her lifetime, and that women are 5 to 8 times more likely than men to be affected.That is a big reason marine-supplement labels get read carefully at this stage of life. It is also the reason we made the design choice described below. We are not trying to address any of this with a supplement.

Iodine 101: a "just enough" nutrient

Iodine is a building block of the thyroid hormones T4 and T3, so the body needs it. But according to the NIH Office of Dietary Supplements, both too little and too much iodine can disturb normal thyroid function, and the two situations can look surprisingly similar. The comfortable middle is a steady, moderate intake.

For adult women, the reference points we use are 150 mcg per day (the RDA for women 19 and over) and a Tolerable Upper Intake Level of 1,100 mcg per day from all foods, water and supplements combined. Needs are higher during pregnancy and lactation (220 and 290 mcg per day). Our formulas are not for use during pregnancy or breastfeeding.

The marine wildcard

Seaweeds are among the richest natural sources of iodine, and they are wildly variable. The NIH reports commercial seaweed ranging from 16 to 2,984 mcg of iodine per gram. A published survey of commercially available edible seaweeds (Teas and colleagues, Thyroid, 2004) documented the same kind of spread. When the source varies by a factor of well over a hundred, the amount in any given capsule is hard to know unless someone measures it.

What we do about it

Every Tide Line formula is built on Everwild SeaMatrix™, our marine mineral complex led by Purple Sea Moss. The approach has four parts:

• A firm ceiling. No more than 30 mcg of iodine per serving, with a target of about 25 mcg. Our Night formula targets about 5 to 15 mcg.
• Controlled at the source. Marine ingredients are chosen and processed to a low-iodine specification. The Matrix itself is built mainly from lower-iodine red and green algae, with a single low-dose brown seaweed extract (10 mg). A full 440 mg serving of the Matrix is designed to deliver roughly 10 to 20 mcg.
• Disclosed on the label. The iodine amount per serving is printed in micrograms on every Tide Line label.
• Tested every batch. Finished-blend iodine is a release requirement, so the number on the label is a measured value.

Even a full daily routine of Tide Line products is formulated to keep combined iodine a small fraction of the 150 mcg RDA and far below the 1,100 mcg upper limit.

We want to be exact about what rests on what. The published literature supports the general science: iodine is essential, seaweed iodine is variable, and excess can affect thyroid function. The specific per-serving numbers rest on our own per-lot testing, which is why we print them and why we test every lot.

What "iodine-conscious" means, and what it does not

Iodine-conscious is a formulation and transparency choice: iodine kept low, disclosed in micrograms and verified by testing. For women who like to keep tabs on their intake, we think that is genuinely useful. It is not a treatment, it is not a claim that our products are suitable for any thyroid condition, and it is not a substitute for the conversation with your own clinician.

A few practical takeaways

• Read the iodine line on the Supplement Facts panel, and be cautious with marine products that do not list one.
• Count iodine from all sources: food, water and supplements together.
• If you have a thyroid condition or take thyroid medication, bring the label to your clinician before you start.
• If you have been diagnosed with hyperthyroidism, formulas containing Wild Purple Sea Moss and bladderwrack are not recommended.

We will keep writing about the science behind our marine ingredients, and we will keep the numbers where you can read them.*

Formulas containing Wild Purple Sea Moss and bladderwrack provide naturally occurring iodine and are not recommended for those diagnosed with hyperthyroidism.

Sources

1. American Thyroid Association. Press Room: Prevalence and Impact of Thyroid Disease. https://www.thyroid.org/media-main/press-room/
2. Teas J, et al. Variability of iodine content in common commercially available edible seaweeds. Thyroid. 2004;14(10):836-841. https://pubmed.ncbi.nlm.nih.gov/15588380/
3. NIH Office of Dietary Supplements. Iodine: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/
4. Farebrother J, Zimmermann MB, Andersson M. Excess iodine intake: sources, assessment, and effects on thyroid function. Ann N Y Acad Sci. 2019;1446(1):44-65. https://pubmed.ncbi.nlm.nih.gov/30891786/
5. Kim Y, et al. The prevalence of thyroid dysfunction in Korean women undergoing routine health screening: a cross-sectional study. Thyroid. 2022;32(7):819-827. https://pubmed.ncbi.nlm.nih.gov/35293242/
6. Leung AM, et al. Potential risks of excess iodine ingestion and exposure: statement by the American Thyroid Association Public Health Committee. Thyroid. 2015;25(2):145-146. https://pubmed.ncbi.nlm.nih.gov/25275241/

*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.