Featured Ingredients

Is Seaweed a Thyroid-Healthy Food?

By: Ginny Mahar

Average Read Time: 3 minutes


We occasionally see the term “seaweed” and “sea vegetables” used as a recommendation for thyroid patients. Eat more seaweed! Incorporate sea vegetables! Seaweed is hot right now, and seaweed-containing products and powders are becoming more common. But before we make a mistake that could undermine our health, spike our antibodies, or lead to serious thyroid problems, let’s get a few things straight about seaweed, particularly iodine in seaweed.

Here’s what I want to shout from the rooftops: NOT ALL SEAWEED IS CREATED EQUAL! Its natural iodine content is the reason seaweed is so often recommended as a thyroid-supportive food, but the thyroid is picky about how much iodine it wants, and the amount of iodine in various types of seaweed varies drastically.

In this post, we’re going to sort out which kinds of seaweed may be safe to eat and incorporate into your well-balanced diet (depending on your individual situation), and why we shouldn’t lump all types of seaweed into the same pile. It’s a matter of semantics and a matter of your safety. We’ll also look at some of the other thyroid-supportive properties of seaweed, and how to determine whether or not incorporating more seaweed into your diet is right for you.

Your Thyroid Is Picky About Iodine

The thyroid is like Goldilocks when it comes to iodine. It reacts badly to both too much iodine, and too little. Not enough iodine can make it hard for the thyroid to do its job of making thyroid hormone. Too much iodine can lead to thyroid dysfunction and aggravate the autoimmune response. The thyroid needs iodine to be just right. ⁠This is why so many thyroid experts warn against taking iodine supplements.

According to team nutritionist, Adrienne Klein:

While some thyroid experts have promoted high doses of iodine to be helpful for thyroid patients, that is not always the case. The American Thyroid Association issued a warning about the risks of too much iodine — especially from supplement forms of iodine, potassium iodide, and kelp.

Getting high doses of iodine can cause similar symptoms as iodine deficiency, like swelling in the neck, inflammation of the thyroid gland, and goiters. Studies have shown that an increased iodine load might also contribute to decreased utilization of thyroid hormones.

Thyroid patients have increased vulnerability to excess iodine, and that could lead to the autoimmune form of hypothyroidism, Hashimoto’s. Even more concerning are studies that show that too much iodine can contribute to thyroid cancer.

Thyrotoxicosis, a life-threatening complication of having elevated iodine levels, can also occur if you take iodine supplements.

If you’d like to dive deeper into the topic of iodine and your thyroid, you can read Adrienne’s full article here: Demystifying Iodine for Thyroid Patients. Also, Thyroid Refresh contributors, Dr. Alan Christianson, and Dr. Izabella Wentz have researched extensively on this topic.

The science is clear that while iodine is critical to thyroid function, we need to be careful not to overdo it. It’s also clear that supplementing with iodine is risky, and should only be done with proper testing, under the guidance of your trusted health care professional. Selenium deficiency, which is common amongst thyroid patients, can also lead to issues from excess iodine.

Yet, the fact remains: Our thyroids do need enough iodine, just not too much.

Iodine in Other Foods

Like so many other aspects of thyroid-specific eating and nutrition, whether or not to incorporate more iodine-containing foods into your diet depends on YOU, the individual.

Some of us in the hypothyroid camp find that incorporating a moderate amount of iodine-containing foods into our diets helps stimulate thyroid function and makes us feel better. Some of us in the autoimmune hypothyroid (Hashimoto’s) or hyperthyroid (Graves’ Disease) camp find that iodine is overly-stimulating, and feel better on a low iodine diet. Also, our diets vary from person to person. Maybe you don’t use iodized salt, eat processed food, or consume seafood regularly. Maybe you live on the coast and consume loads of iodine-containing foods regularly. Several factors come into play in regards to your iodine consumption.

Whether or not incorporating more iodine into your diet is right for you, depends on you, and is best discussed with your trusted nutritionist or doctor.

Some iodine-containing foods include:

Eggs (24 mcg)
Tuna (17 mcg)
Turkey (34 mcg per 3 oz)
Shrimp (35 mcg per 3 oz)
Cod (99 mcg)
Prunes (13 mcg per 5 prunes)
Cranberries (400 mcg per 4 oz)
Skin-on potatoes (60 mcg per medium potato)
Lima beans (16 mcg per 1 cup cooked)
Bananas (3 mcg)
Green peas (6 mcg per 1 cup cooked)


Iodine in Seaweed

Seaweed is one of the most commonly recommended food sources of iodine, and one of the most common foods recommended for thyroid patients. BUT, there are important details to consider in regards to seaweed. While seaweed, in general, does contain iodine, the amount varies widely among types of seaweed; so much so, that we can put our health at risk if we don’t understand the difference between these apples-to-oranges varieties.


The recommended daily intake of iodine is 150 mcg for most adults. Dietary intake can vary widely, day-to-day, but the NIH says the upper limit for iodine intake is 1,100 mcg, again for most adults. Also, the amount of iodine in seaweed can vary significantly depending on where it’s grown.

There are several varieties of edible seaweed, but we’re going to focus on a few of the most commonly used and widely available:


These are the dried, papery, seaweed sheets that are used to wrap your favorite sushi roll. Also, those dried “Seaweed Snacks”? Same stuff.

1 sushi-size sheet of nori contains approximately 24 mcg of iodine, or 16% DV. 


When you order the seaweed salad from your favorite sushi bar, wakame is typically what you get. It’s also usually what’s floating around in your bowl of miso soup.

We typically eat bigger portions of wakame, and therefore get a significantly higher amount of iodine, at 840 mcg per 1/4 cup serving, or 560% DV. 

Atlantic Dulse:

(Rhymes with “pulse.”) Dulse is a leafy red variety of seaweed that is available fresh, dried, or in flakes. Gourmands treasure its umami flavor that many say is reminiscent of bacon.

1 gram of dried dulse contains 150 – 300 mcg of iodine, or 100% – 200% DV. 

Kelp, aka Kombu:

This is the stuff that grows in vast ocean forests. Dried kelp leaves are sometimes used in Japanese cooking to flavor soup stocks (like dashi broth), before being discarded. It’s not considered safe to eat in the same way as other types of seaweed due to its extremely high iodine content.

Just 1 gram (about half a teaspoon) of kelp contains 2,984 mcg of iodine. That’s 20x the recommended daily intake, nearly 3x the safe upper limit, and 2000% DV in a teeny-tiny amount.

So, before you go adding a big scoop of kelp powder to your smoothie, thinking you’re doing your thyroid a favor, remember…not all seaweed is created equal.

Other Health Benefits of Seaweed:

The thyroid-healthy properties of seaweed go far beyond its iodine content. In addition to iodine, some of the other key thyroid-supporting nutrients found in various types of seaweed include tyrosine, potassium, iron, magnesium, zinc, selenium, and B vitamins. Seaweed also contains some rare anti-inflammatory compounds, anti-cancer properties, can help balance our blood sugar and is highly supportive to our gut health.

While some information (and misinformation) has spread online regarding things like heavy metals in seaweed, or radiation in seaweed caused by the Fukushima disaster, famous food researcher, Dr. Sarah Ballantyne, PhD (aka Paleo Mom) did a deep dive on this topic, and feels that seaweed is still a safe and amazing food for our health. One of the primary health benefits of seaweed is that they contain loads of micronutrients, including antioxidants, unique polyphenols, unique dietary fibers, and several trace minerals that are hard to get from other foods.

It’s easy to see why seaweed so often takes the nutritional spotlight, and why we may benefit from mindful consumption of it.


Bottom Line:

Because the thyroid needs adequate iodine to function properly, moderate amounts of nori, wakame, and even dulse seaweed can be part of a nutrient-dense, thyroid-healthy diet (taking your other bio-individual factors into consideration). When it comes to seaweed consumption, it’s important to keep in mind that kelp contains dangerously high levels of iodine. That’s why the term “seaweed” or “sea vegetables” shouldn’t really be used as a blanket recommendation for thyroid patients, without clarifying the vast difference between safer choices like nori, wakame, and dulse, and potentially dangerous kelp.

I hope this has informed and empowered you to make smart, safe, and thyroid-healthy decisions around seaweed consumption. Knowing the details and variances between nori, wakame, dulse, and kelp is critical knowledge that will enable you to do just that!

About the Author

Thyroid Refresh Co-founder Ginny Mahar is the mom and recipe blogger formerly known as Hypothyroid Chef. After struggling with the residual symptoms of Hashimoto’s for over four years, she embarked on her own process of adopting a thyroid-specific diet and lifestyle. Within one year, she restored her vitality and lowered her thyroid antibodies by half. Ginny is a passionate advocate of supporting others on their journeys toward better health. She is a Cordon Bleu trained chef, cooking instructor, writer, and entrepreneur.