Health Benefits & Dangers of Seaweed

Seaweed is basically sea vegetables that are just your typical algae that grow in the sea. They are not only a food source for the various ocean life, but even humans can consume seaweed for the many health benefits associated with these sea vegetables. Seaweed is usually found in a wide range of colors, from brown to black to even red to green. Seaweed is found almost all throughout the world and it grows along the rocky shorelines. It is most commonly consumed in Asian countries such as China, Korea, and Japan. Seaweed is extremely versatile and due to this, it is used in a wide range of dishes such as stews, soups, sushi rolls, smoothies, supplements, and even salads.

Health Benefits of Seaweed

Health Benefits of Seaweed

Let us take a closer look at some of the surprising health benefits of seaweed.

Seaweed is an Excellent Source of Vitamins and Minerals

There are many different types of seaweed available and the surprising part is that each one of these seaweeds has a unique set of nutrients that provide various health benefits.

For example, studies have shown that 1 tablespoon (roughly 7 grams) of dried spirulina (a type of seaweed) contains the following.

  • 20 calories
  • 4 grams of protein
  • 1.7 grams of carbohydrates
  • 0.5 grams of fat
  • 0.3 grams of fiber
  • 15% of the Recommended Daily Intake (RDI) of riboflavin
  • 11% of the RDI for thiamin
  • 11% of the RDI for iron
  • 21% of the RDI for copper
  • 7% of the RDI for manganese

Just by sprinkling a little bit of dried seaweed on top of your food, you can not only enhance the taste and flavor, but it also adds an extra texture to the meal, while boosting the intake of vitamins and minerals.

Seaweed contains small amounts of vitamins A, E, K, and C, as well as zinc, sodium, folate, magnesium, and calcium.

While seaweed might not contribute too much to the RDIs mentioned above, but still using seaweed as seasoning at least two times a week is the easiest way of adding these nutrients in your diet.

There is also some protein present in some types of seaweeds, such as chlorella and spirulina. These seaweeds contain nearly all of the essential amino acids that your body needs, ensuring that you are getting the entire range of essential amino acids that the body requires.

At the same time, seaweed is an excellent source of omega-3 fats and vitamin B12.

Dried purple and green colored seaweed, in fact, contains a rich amount of vitamin B12. A study done by the Kochi Women’s University in Japan found that there is 2.4 mcg or 100 percent of the vitamin B12 RDI present in only four grams of nori seaweed.

However, regardless of all the vitamins and minerals contained in seaweed, there is still a raging debate going on about whether your body can actually absorb and use the vitamin B12 found as well as the other vitamins and minerals found in seaweed.

Seaweeds Supports Thyroid Function

The thyroid gland is one of the most important glands of the body as it releases hormones that help in energy production, control growth, have a role to play in reproduction, and also repair the damaged cells of your body. The thyroid gland typically relies on iodine for making these hormones. When sufficient amounts of iodine are not present, then you may start to experience changes that indicate abnormal functioning of the thyroid gland, such as weight changes, swelling of the neck and fatigue over a period of time.

Generally, the RDI for iodine is 150 mcg per day.

Seaweed is unique in that it absorbs a lot of concentrated iodine from the ocean. The iodine content in seaweed varies depending on which type of seaweed you are consuming, where the seaweed has been growing, and how it has been processed. It is estimated that only one dried sheet of seaweed can contain nearly 11 to 1,989 percent of the recommended daily intake of iodine.

Here’s a look at the average iodine content found in three commonly found dried seaweeds.

  • Kombu Seaweed. 2523 mcg per gram or 1,682 percent of the RDI
  • Nori Seaweed. 37 mcg per gram or 25 percent of the RDI
  • Wakame Seaweed. 139 mcg per gram or 93 percent of the RDI

Apart from these three seaweeds, kelp is known to contain one of the highest levels of iodine. Even a single teaspoon, or 3.5 grams, of dried kelp, is known to contain nearly 60 times the RDI for iodine.

Seaweed is also rich in an amino acid known as tyrosine, which is also required by the body alongside iodine for making the two main hormones that keep the thyroid gland functioning properly.

Seaweeds are Rich in Antioxidants

Antioxidants protect the body from unstable substances known as free radicals. The intake of seaweed, which are rich in antioxidative properties, will prevent the body from damage being caused by these free radicals.

Excess production of free radicals is believed to be one of the big underlying causes of many diseases such as diabetes and cardiovascular disease.

Apart from containing the antioxidants vitamins E, C, and A, seaweed also includes a lot of beneficial plant-based compounds, such as carotenoids and flavonoids. Both carotenoids and flavonoids are proven to provide protection against damage to the cells by free radicals.

Research has particularly been focused on a type of carotenoid known as fucoxanthin. Fucoxanthin is particularly found in brown algae such as wakame, and it is known to have nearly 14 times more antioxidant properties as compared to vitamin E. Studies by the Hokkaido University in Japan has shown that fucoxanthin has protective properties that protect cell membranes even better than the protection provided by vitamin A.

However, the human body is unable to absorb fucoxanthin properly, which is why it should be consumed together with fat to boost the absorption process.

Good Gut Health Benefits of Seaweeds

Gut bacteria have a huge role to play in maintaining your overall health. Research estimates that there are more cells of bacteria in your body as compared to human cells. If an imbalance occurs between the ‘good’ and the ‘bad’ bacteria cells in the gut, then it can cause many illnesses.

Seaweed is known to be a great source of fiber, which helps in boosting your gut health.

In fact, fiber makes up for around 25 to 75 percent of the dry weight of seaweed. This percentage is much higher than the fiber content present in most vegetable and fruits.

Fiber is known to resist digestion, which is why it helps prevent a spike in your blood sugar levels after a meal. Fiber is also a good food source for the friendly bacteria present in your large intestine.

Furthermore, there is certain sugar in seaweed known as sulfated polysaccharides, which help increase the growth of the ‘friendly’ gut bacteria.

These sulfated polysaccharides also boost the production of SCFA (short-chain fatty acids). SCFAs are known to provide nourishment and support to the cells that line the gut.

Weight Loss Benefits of Seaweed

As mentioned above, seaweed is a rich source of fiber. Fiber does not have any calories, making it a great source of losing weight. The fiber present in seaweed also promotes a slower emptying of the stomach, helping you feel full for a longer period of time, thus also delayed any hunger pangs.

Apart from the presence of high levels of fiber, seaweed is also known to have certain anti-obesity effects. Many animal studies have shown that the substance fucoxanthin present in seaweed helps decrease body fat. In fact, one animal study found that the rats who were given fucoxanthin ended up losing substantial weight, while the rats who were given the control diet without fucoxanthin did not lose weight. The study was carried out by the Laboratory of Biofunctional Material Chemistry at the Hokkaido University in Japan. Their results found that fucoxanthin increases the expression of a specific protein that helps metabolize fat in these rats.

While other animal studies have also reached similar conclusions, there have been no human studies done till date that prove the same effects in humans as well, though the effects are likely to be the same in humans as well.

Furthermore, fucoxanthin has also shown to dramatically lower blood sugar levels in rats, another factor helping boost weight loss.

It is, however, important that the same findings are replicated in human studies to conclude this with certainty.

Are There Any Dangers of Consuming Seaweed?

While seaweed is considered to be a very healthy food to have, there are certain potential dangers of consuming too much seaweed. These include.

Seaweed contains a very large amount of iodine. In some types of seaweed, the amount of iodine can be potentially dangerous. However, on the other hand, the high iodine intake of the Japanese population is believed to be the reason why they are amongst the healthiest race of people in the world. The daily average intake of iodine amongst the Japanese population is expected to be around 1,000 to 3,000 mcg, which is nearly 667 to 2,000 percent of the RDI for iodine. This is known to be a significant risk for people who consume seaweed every day because 1,100 mcg of iodine is said to be the tolerable upper limit of iodine consumption for adults on a daily basis. The saving grace here, though, is that in most Asian cultures, seaweed is generally consumed along with foods that inhibit the uptake of this excess iodine by the thyroid gland.

Seaweed also has a heavy metal load. This means that seaweed is able to absorb and store minerals in very concentrated amounts. This is a significant health risk because seaweed also contains very large amounts of some toxic heavy metals such as lead, mercury, and cadmium. The heavy metal content in most seaweeds is typically below the maximum concentration that is allowed in most countries and studies have found that the amount of metals contained in the common types of seaweeds that are consumed are unlikely to pose any major health risk. Nevertheless, if you are consuming seaweed on a daily basis or regularly, there is a potential risk of these heavy metals building up in your body over a period of time. It is better to buy organic seaweed, which is likely to contain a lesser amount of heavy metals.


Seaweed is becoming a popular ingredient in many types of cuisines all around the world. Seaweed is the best source of dietary iodine you can get and it will help support your thyroid gland tremendously. Apart from iodine, seaweed also contains many important vitamins and minerals such as B vitamins, vitamin K, iron, and zinc. It is also rich in antioxidants, which protects the cells of your body from damage caused by free radicals. However, keep in mind that too much of iodine can also harm your thyroid function. This is why for achieving the best health benefits from seaweed, enjoy this ingredient in small amounts on a regular basis.

Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:April 5, 2019

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