Kombu: Edible Kelp for Digestion, Thyroid Function & More

July 24, 2023

It’s no secret that most Americans consume an unhealthy diet, which is perhaps the leading reason there are so many health issues in the U.S. In fact, compared to Japan, Americans are more likely to develop heart disease and cancer.

But if we change the way we eat to reflect more of the healthier countries out there, perhaps we can begin to reverse this trend. Kombu, a Japanese staple, is a good place to start.

Kombu is an edible kelp found in the sea forests, also known as kelp forests. These forests are very beneficial by providing an important ecosystem for the organisms that live between the sea floor and the surface of the ocean. As such, the seaweed absorbs a vast array of nutrients, making it a powerful, health-promoting food. That’s right, seaweed is the new superfood — so let’s find out just what amazing abilities kombu holds.

What Is Kombu?

Most popular in East Asia, kombu is an edible kelp or seaweed that provides lots of nutritional benefits straight from the sea, making it yet another super seaweed similar to its cousin, wakame. The Japanese may call it konbu, while the Koreans refer to it as dashima, and the Chinese call it haidai.

Kombu comes from the Laminariaceae family, as do wakame, arame and kurome — other forms of sea kelp. Most kombu is from the species Saccharina japonica (Laminaria japonica) and is extensively cultivated on ropes in the seas of Japan and Korea. In fact, more than 90 percent of Japanese kombu is cultivated, mostly in Hokkaidō, but also as far south as the Seto Inland Sea.

Kombu offers tons of minerals, such as calcium, copper, iron, magnesium, manganese, molybdenum, phosphorus, potassium, selenium, vanadium and zinc. Brown algae, like this seaweed, offer a rich source of iodine and vanadium, also a mineral found in sea vegetables, may help convert existing blood sugars into storable starches, which could lower the risk of type 2 diabetes.

Here are a few of the most common types of seaweeds and algae that are used as foods and/or supplements:

Hijiki
Wakame
Ogo
Kelp
Nori
Arame
Dulse
Sea moss
Spirulina
Blue spirulina
Bladderwreck

Nutrition Facts

One-fourth cup serving of dried kombu (7 grams) contains about:

Calories: 17
Total Carbohydrates: 3 g
- Fiber: 1 g
- Sugar: 0 g
Total Fat: 0 g
Protein: 1 g
Sodium: 161 mg (7% DV*)
Calcium: 60 g (6% DV*)
Iron: 1.1 mg (6% DV*)
Vitamin C: 1.2 mg (2% DV*)
Vitamin A: 50 IU (1% DV*)

*Daily Value: Percentages are based on a diet of 2,000 calories a day.

What about iodine? Nutrition data was not available from the USDA. One study determined that kombu contains 1,542 micrograms of iodine per gram. That would make a 7 gram serving as 10,794 micrograms (7,196 percent DV).

Benefits

1. Improves Digestion and Reduces Gas

Kombu contains certain amino acids that can help break down the heavy starches found in foods like beans. This allows for them to be digested much easier. The glutamic acid found in this seaweed provides its pleasantly savory flavor while the fiber helps digestion overall.

Kombu is also able to minimize the gas-producing effects beans may have. For those who struggle with intestinal gas, it’s often due to a missing enzymes required to break down raffinose sugars that are found in beans. The bacteria in the gut loves these sugars, releasing hydrogen and carbon dioxide and therefore gas and even bloated stomach as well. Kombu contains the digestive enzymes that can offer a more pleasing experience when consuming legumes.

2. Potentially Helps Prevent Cancer

Sea vegetables may offer cancer-preventing benefits. We know that inflammation and chronic oxidative stress are risk factors for development of cancer, and because kombu, and other sea vegetables, are known to provide anti-inflammatory benefits, scientists are examining sea vegetables as cancer-fighting foods.

A Chinese study published in the International Journal of Biological Macromolecules revealed that kombu may have an antitumor effect on liver cancer. Tumors were inhibited in mice who were injected with the seaweed extract, with researchers concluding that “LJP exerts antitumor effect and can be used as a therapeutic agent for cancer.”

3. Aids in Staving Off Anemia

Iron plays an important role in body function due to its role in the production of hemoglobin, which is what carries oxygen through that blood as well as provides healthy cells, skin, hair and nails. Kombu may be able to provide the much-needed iron to maintain good health.

Anemia caused by an iron deficiency is quite common and occurs due to the lack of healthy red blood cells. The missing component causes the body to lack hemoglobin production. These red blood cells have the job of carrying oxygen to the tissues throughout the body while removing carbon dioxide.

If you are low in iron or out of your stores, you may feel tired and have shortness of breath. Those most at risk are women who menstruate, are pregnant or breast-feeding, anyone who has had major surgery, vegans and vegetarians, or someone who has ulcerative colitis to, name a few. Thankfully, kombu is an iron-rich food that can help prevent both iron deficiency and anemic symptoms.

4. Improves Thyroid Function

Kombu not only contains iodine — it has the highest amount of iodine of all the seaweeds, making it one of the most iodine-rich foods in the world. Iodine is important in our diets for healthy hormone production and a properly functioning thyroid. It may even help anyone who battles hypothyroidism, though monitoring intake is critical for if undergoing serious thyroid problems.

According to a report published in Thyroid Research, iodine is crucial for thyroid hormone synthesis and believed to provide antioxidants that may even help prevent heart disease and cancer. Seaweeds have the ability to soak up the natural salts found in the ocean with some varieties containing over 30,000 times the iodine concentration found in the deep blue sea.

The American Thyroid Organization states that because our bodies don’t naturally make iodine, it’s important to make sure you get the daily requirements in order to have a properly functioning thyroid. About 40 percent of people in the world are at risk for iodine deficiency, making kombu a great way to incorporate it into your diet.

5. Combats Rheumatoid Arthritis

Kombu contains fucoidan, which is a sulfated polysaccharide found in various species of brown algae and brown seaweed. A study conducted by the Affiliated Hospital of Changchun University of Traditional Chinese Medicine’s Department of Medical Affairs investigated the effects of kombu against rheumatoid arthritis by evaluating the cell invasion process of the seaweed.

It appears that the arthritis-causing inflamed cells were significantly impaired by the fucoidan treatment, reducing the survival of the bad cells. Because of this, researchers believe it’s a possible treatment for rheumatoid arthritis symptoms.

How to Use

Kombu, dried over a fire until crisp, is usually found in strips, squares or circles. These pieces are also known as kiri. This seaweed can be found as a fine powder called Saimatsu. Doshi kombu is a form of stock used for soups, and there is even a form used as fertilizer.

To cook with it, you can add a three- to four-inch strip to beans as they cook, or add it to your soup recipes. It’s an edible sea vegetable, so once the cooking process has completed, pull out the kombu, chop it into small pieces and place it back into the pot.

If you add it to precooked beans or cans of soup, soak it for about 20 minutes, then add the seaweed and the soaking water to the pot to get all the minerals.

It’s best to purchase organic kombu to avoid chemical residues.

Recipe

You can make a delicious stock using kombu that can be incorporated into almost anything from soups to beans and more. This recipe is about as simple as it gets, too.

Ingredients

4–6 cups water
6-inch piece dried kombu

Directions

In a pot on the stove, combine 4–6 cups of water and a 6-inch piece of dried kombu. (Tip: Lightly score the the kombu to release more flavor.)
Allow the kombu to soak for about 15–20 minutes, then bring to a simmer, uncovered, over medium heat.
Remove the kombu from the pot, and save it to use in the another dish.

You can use the kombu one or two more times before discarding. To reuse, add to soup or beans, or repeat this process. If you want to take it even further for optimal benefits, combine it with a bone broth recipe for an amazing pot of nutrition!

History

It’s been reported that it’s somewhat difficult to find historical information regarding seaweed because it easily decomposes. However, some evidence has pointed toward the wakame seaweed, which has been found in the ruins of the Jomon Period. This information, and some documentation that dates back as far as 12,000 B.C., has lead researchers to think that kombu was eaten at about that time, too.

Kombu was offered as a tribute to the Yamato Court, among others, but it was during the Muromachi Period that a new drying technique was discovered, allowing the kombu to be stored for a few days or so. This gave way to exportation of it as a product. Kombu is also a staple of Okinawan cuisine, which differs from mainland Japanese cuisine.

It wasn’t until 1867 that the word “kombu” first appeared in an English-language publication. It took some time before dried kombu was exported from Japan, occurring in the 1960s. Asian food shops and restaurants were the first to offer it — however, now it can be found in some supermarkets, health food stores and specialty shops.

It’s pretty well-known that the Japanese have a long life expectancy, partially due to the low rate of some cancers. Part of what makes a difference is their high iodine intake from seaweeds. Numerous sources cite some pretty phenomenal Japanese health statistics, which are believed to have a relation to the high seaweed intake:

The Japanese average life span is about five years longer than U.S. averages.
It was reported that in 1999, breast cancer death rates were three times higher in the U.S. than in Japan.
Studies showed that breast cancer rates, in those who came to the U.S. from Japan, jumped from 20 per 100,000 to 30 per 100,000.
The rate of prostate cancer in the U.S. in 2002 was 10 times higher than in Japan.
Deaths associated with heart conditions in both men and women aged 35–74 are higher in the U.S. than in Japan.
Infant deaths were reported as 50 percent higher in the U.S. in 2004 than in Japan.

Precautions and Side Effects

As noted earlier, if you suffer from thyroid problems or are on potassium medication, please take extra caution by consulting your healthcare professional. All seaweed contains iodine, and with kombu’s high iodine content, it could result in daily consumption of about 1,000 times more than recommended.

These high levels may suppress thyroid function. As consuming too much iodine on a regular basis, thyroid hormone synthesis can be inhibited. Some could even experience toxicity, depending on how much you consume and if you have underlying issues. Excessive consumption can cause goiter, elevated TSH levels, and hypothyroidism can result.

U.S. health officials recommend 150 micrograms of iodine per day for adults, with the upper limit around 1,100 micrograms. Just one gram of raw dried kombu contains 1,542 micrograms. While raw dried kombu contains the most iodine per microgram, keep in mind that cooking kombu reduces its iodine content.

A study of healthy Japanese people, however, points out that seaweed consumption is common, with an average of 1,000 to 3,000 micrograms per day.

Final Thoughts

Kombu is an edible kelp found in sea forests that’s been shown to improve digestion, reduce gas, potentially help prevent cancer, aid in staving off anemia, improve thyroid function and combat arthritis.

It can provide a delicious addition to soups, stews and more while offering quite a nutritional bundle, given that it’s filled with useful minerals. Consider trying one of the recipes above, and if you aren’t so sure, use half the amount to start.