Four Surprising Nutrients In Seaweed

Photo credit: jonkriz via / CC BY

If you’ve noticed lately, seaweed seems to be getting a lot of publicity. As Korean food becomes more popular (Korean BBQ) and sushi becomes more a norm (and not gross people out), you’re going to see seaweed a lot more. Instead of reaching for chips or some other kind of unhealthy snack, you see more people reaching for seaweed. Why not? They’re cheap, they’re relatively healthy (when you don’t take into account the salt on them), and you get the crunch satisfaction. Seaweed has been used in Asian cuisine for millennia. We grew up eating seaweed all the time, so it’s nothing new to me. Other than the usual associations of seaweed, did you know that it’s packed with four very important nutrients? No? Well, my friend, read on!

1. Iodine

We all know iodine because of salt. Do y’all remember Morton’s Iodized salt with the picture of the little girl under the umbrella? I’ve always wondered why she was under an umbrella holding the salt upside down. If you click the link in the caption, there’s a pretty cool history behind the logo as well.

Morton's iodized salt
Morton’s Iodized Salt Source: Retro Planet

“Iodine is a good example of a trace mineral whose deficiency creates a disease that is easily corrected by resupplying it in the diet.” Because of a number of goiter cases that occurred, Iodine was added to table salt in 1924. The “Goiter Belt” included the Northern part of the United States where the soil was depleted of iodine. “The iodine content of plant foods varies widely since it depends on how much is in the soil. The farther food is grown from the ocean, the less likely it is to be rich in iodine.” 

goiter belt
Goiter Belt in the United States Source: The Salt Institute

Iodine is needed because it’s a requirement to make thyroid hormones. There’s a delicate balance that you need. Not too much and not too little. Your thyroid hormones help with everything from your metabolism to nerve formation to cell respiration to your mental state. That’s a lot! So, it’s not just your thyroid that needs iodine. Your entire body needs it.

It’s important for pregnant women also. A condition called Cretinism is caused by hypothyroidism (not enough thyroid hormones) is linked to an iodine deficiency. Cretinism is “a condition of severely stunted physical and mental growth.”

There are a number of sources where you can get iodine. “The salt that is added to processed foods by manufacturers is usually not iodized.”4 Some sources are milk, cheese, eggs, and yogurt. This is all if the cow and chicken are exposed to iodine by having it in their feed or grazing on plants grown in iodine-rich soil. Some vegetables may also contain iodine, but again that’s if the vegetable was grown in iodine-rich soil. So, it’s probably best to put a little bit of iodized salt on your food or drown it in salt like I do, or you can take a small supplement. Sea vegetables is a rich source of iodine. So you can snack on some seaweed a few times a week.

RDA for iodine
AI Levels and RDAs for Iodine

2. Calcium

calcium, milk, nutrient in seaweed

Calcium is usually associated with milk and how it’s needed for healthy bones and teeth. It’s the most abundant mineral in the body and plays an important role in many functions in the body. The most widely-known function for calcium is helping with healthy bones and teeth. However, calcium is so much more complicated and important. It helps with heart function, reducing cardiovascular disease, menstrual problems, nerve conduction, cell division, and much more.

In order for calcium to work properly and to be absorbed, it needs a few partners like magnesium and vitamin D. Calcium absorption is sensitive so something like stress or too little exercise can affect its absorption. Anywhere from 30-80% of calcium could end up being excreted from the body and not absorbed.

One thing to look for is phosphorus. When you have too much (phosphoric acid is added to soft drinks), you can lose calcium through the urine, and then your body will pull it from your bones.

Calcium is, of course, found in fortified plant milk and juices, figs, tahini, and milk products. However, it’s also found in plant sources as well: broccoli, collard greens, turnip greens, bok choy, kale, almonds, sunflower seeds, sesame seeds, blackstrap molasses, tofu (when it’s made with calcium-sulfate), and kelp.


    • Make sure your diet is rich in protein by including at least three servings of legumes in menus every day.
    • Eat plenty of calcium-rich foods. Aim for 3 cups per day of foods that provide calcium–leafy greens (collard greens, turnip greens, kale, and bok choy), fortified plant milks and juices, calcium-set tofu, soybeans, tempeh, and figs. Almond butter and seasmae tahini are other good calcium sources.
    • Get adequate sun exposure or take a supplement providing at least 600 IUs of vitamin D.
    • Pack your menus with fruits and vegetables.
    • Eat lots of leafy greens–all different kinds–for their calcium, vitamin K, magnesium, and potassium.
    • Exercise every day and include strength-training in your regimen. If you are limited in the type of exercise you can do, talk to a physical therapist to find a plan that fits your needs.
    • Cut back on sodium by avoiding processed foods and limiting added salt in the foods you prepare yourself.
    • Keep alcohol intake moderate.
    • Stop or cut back on smoking.

3. Potassium

Potassium is another mineral that’s important to the body and is one of the electrolytes (the others are sodium and chloride).


With sodium, potassium helps with maintaining the water balance in the body. It helps with nerve pulses, regulates blood pressure, carbohydrate metabolism, and for muscle growth. It’s crucial to cardiovascular and nerve functions.

“Potassium-rich foods help to balance out acid-causing dietary factors and may reduce calcium loss from bones. One reason why vegans have less acidic urine might be because the main sources of protein in their diet–legumes–are also rich in potassium. It’s difficult to meet potassium needs if you aren’t eating a diet that’s rich in fruits, vegetables, and legumes.”

bananas, potassium

Potassium is found in a lot of fruits and vegetables like bananas, spinach, oranges, broccoli, peas, whole grains, legumes, avocado, beet greens, swiss chard, sweet potatoes, and tomato juice. However, it’s easily lost during the cooking process so be careful.

4. Iron


Iron is something else that plant-based eaters need to be conscious about. Protein and iron are automatically associated with flesh foods. With the case of iron, the type of iron that’s more easily absorbed is only found in meat.

Plant foods are rich in iron, and vegans typically have high iron intakes. However, iron from legumes, grains, nuts, and seeds is bound to phytate, a naturally occurring compound that reduces mineral absorption. Vitamin C can break the bond between iron and phytate, though, freeing the iron and increasing it’s absorption.

The form of iron that’s found in meat is heme iron. What’s in vegetables is nonheme iron, which isn’t absorbed and utilized all that well.

Meat foods improve absoption, possibly by stimulating increased stomach acid production and by the fact that the iron contained is already bound into muscle and blood issue in the form of the iron proteins myoglobin and hemoglobin.

The primary function of iron is to make hemoglobin. Hemoglobin carries oxygen to your tissues. “Myoglobin is similar to hemoglobin that it’s an iron-protein compound that holds oxygen and carries it into the muscles, mainly skeletal muscles and the heart.” Iron is also needed by enzymes for energy production and protein metabolism.

Foods most concentrated in iron
Source: Haas, E., with Levin, B. Staying Healthy with Nutrition: The Complete Guide to Diet and Nutritional Medicine. New York: Celestial Arts, 2006
Messina, V. with Fields, JL. Vegan for Her: The Woman’s Guide to Being Healthy and Fit on a Plant-Based Diet. Boston: Da Capo, 2013.

In closing, please don’t take what I’ve written as the gospel truth. I am not a trained professional. I haven’t finished my schooling yet. I’m just a person who’s curious about nutrition like you.


1. Messina, V. with Fields, JL. Vegan for Her: The Woman’s Guide to Being Healthy and Fit on a Plant-Based Diet. Boston: Da Capo, 2013.

2. Haas, E., with Levin, B. Staying Healthy with Nutrition: The Complete Guide to Diet and Nutritional Medicine. New York: Celestial Arts, 2006
























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