What is Nori? Nutrition, Health Benefits, Side Effects and More

Nori, (Japanese for edible seaweed) is produced from Porphyra, a type of seaweed and is widely used in Japan.  In that country, three hundred and fifty thousand tons of Nori are produced from over 220 square miles of the sea.  The value of this crop is estimated to be in the billions of dollars! This makes it very likely that you have tried nori before and to learn more about it continue reading to find out all about it, how it’s made, any benefits and any side effects of eating it.

nori sheet

How is Nori produced?

The reason for the vast production of Nori in Japan is obvious, it is a big part of Asian diets so no wonder producing Nori has become a highly mechanised process, in Japan.

The production starts by placing Nori seeds into huge nets on land and then taking them out to sea in large tanks. It takes less than two months for the small Nori fronds to grow to about 15 cm in length. Monitoring at this stage is constant, to guard against susceptibility to disease.

The temperature of the water and its saline content can also affect the young plant.  Once the Nori crop is ready to harvest it is never sold as a fresh product but is made into sheets.

After washing with fresh water, it is shredded reducing the individual pieces to sheets of about 0.5cm x 1cm.  Fresh water is added and the mixture poured into a frame.

The last step in the process is the application of heat that produces a solid sheet product that is ready to ship.

Is nori Vegan?

Japanese Seaweed Yaki-Nori is considered to be vegan, as seaweed is the only listed ingredient. Another type called Aji-Tsuke Nori (flavoured Nori) can have crab, bonito, shrimp, and other flavourings so would not be suitable for a vegan diet. Korean Nori labelled as flavoured is fried with salt and is also OK for a vegan.

Is nori Kosher?

The safest way to buy Nori that is kosher is to buy it from a store or a source that has done the legwork for you to ensure no shellfish is involved in its production!

Does nori have any health benefits?

There is no doubt that this seaweed product offers health benefits being very rich in micronutrients, offering more minerals and vitamins than most fruit and vegetables! It’s full of vitamins C and B12 and also contains the minerals iodine, calcium, magnesium, zinc and iron.

Iodine is a very important element that your body needs to make thyroid hormones. These hormones help to control your body’s metabolism and are involved in other important functions. Unfortunately, some people are at risk of iodine deficiency especially those who don’t eat fish and seafood which are good sources of iodine. For them, it’s a good idea to eat nori or other seaweed types regularly in order to prevent deficiency and symptoms such as goitre, dry skin and hypothyroidism.

B12 vitamin, also found in nori, is important for the healthy functioning of the nervous system and it’s also involved in the production of red blood cells. Vegans who don’t eat any animal products struggle to get enough of this important vitamin through diet alone but eating nori regularly can certainly help them meet the recommended daily intake (as long as they also get B12 from other sources such as fortified vegan foods and possibly supplements).

Nori is not only beneficial for your thyroid system but it has also been shown to reduce cholesterol levels in some animal studies.

What’s more, being rich in calcium and magnesium, nori helps to keep our bones healthy and may even help to reduce the symptoms of existing joint conditions such as osteoarthritis.

Yes, nori has many health benefits!

More nutritional information about Nori

Calories and carbs

Nori is very low in calories. For only 9 calories you can feast on ten sheets of Nori (about 26 gm.).  This amount of Nori will also contain 1.3g of carbs, 1.5g of protein, fibre at 0.1 grams, and a minuscule 0.1g of sugar.  Being low in carbs, Nori sheets are ideal for a Ketogenic diet.

Is nori gluten-free?

Nori in sushi will be gluten-free provided no extra ingredients are added for flavour such as teriyaki or soy sauce. You can consider the original unflavoured Japanese Nori, gluten safe. However, Korean-made Nori often has soy sauce flavouring and cannot be considered gluten safe.

Iodine content in nori

Unlike the content of iodine found in brown seaweed, the iodine content in Nori (often used for sushi rolls) is a lot lower. Nori iodine content will vary between 16–43 mcg/gm., and around 10–30% of the daily-recommended intake. (1).

Is nori low FODMAP?

Any seaweed, including Nori, as well as products like rice will be considered naturally low FODMAP.

Is Nori good for you?

Well, packed as it is with nutrients and all good things Nori is certainly good for you.  There have been a lot of studies and one, carried out at the Universidad Complutense in Madrid, Spain concluded that eating seaweed could have anti-mutagenic as well as anticoagulant effects and antioxidant properties. It also has a strong role to play in the modification of lipid metabolism in the body.  (2)

Can you eat Nori when you are pregnant?

One aspect of eating seaweed when you are pregnant is that it is a significant source of Iodine. However, there are around ten thousand different types of seaweed, worldwide that you could buy.  Along with the different types of seaweed there are also differences in the iodine they provide.  The risk of taking in too much iodine is relatively small, but it would always be advisable to make sure that the seaweed that you use is from a trusted and reputable source.  As in all things, if you are not sure, consult your doctor.

Does nori have any side effects?

While it is acknowledged that eating Nori or other seaweed might help to decrease cholesterol levels and lower blood sugar as reported in a 2008 study published in Nutrition Research and Practice (3), you should always seek medical advice if you plan to eat large amounts of seaweed such as nori to check it will not interact adversely with any medication you are on.

Tummy Troubles

There have been some reports of people who eat seaweed having some abdominal pain, nausea, and diarrhoea and bloating.  However, severe side effects reported, are rare.

Iodine Toxicity

The type of seaweed you take will determine the level of iodine provided. Some seaweed, however, can deliver as much as 4.5 gm.  Too much iodine can lead to thyroid problems and the development of a goitre.  An acne type rash has also been reported, so if you do suffer from any unusual effects like these, you should always see your doctor without delay.

High in salt

Being from the sea, seaweed is always going to be high in salt, which in turn is known to cause high blood pressure.  Supplements can be especially high in salt, so if you suffer from high blood pressure, or even if you don’t, it is always best to keep an eye on how much salt is in the Nori that you eat.

Heavy Metal Contamination

If the Nori you eat has been grown in the water where heavy metals or arsenic are found then they might be absorbed into the Nori.  The ingestion of too much of these kinds of contaminants can have very serious effects on your health.  Checking that the Nori product you are buying is certified to have been grown in uncontaminated waters is always the best idea.

Interaction with medicines

We mentioned interaction with medicines although, in fact, most medications will not interact with Nori.  However, medication to thin the blood, including Warfarin can be affected by the high vitamin K levels in Nori.  That is because blood thinners work by disrupting the way that vitamin K works in the body.  If you do increase vitamin K intake, by eating Nori then it might also be necessary to increase the dosage of your medication so that it still works.

Types of nori

Nori can come in many different grades and qualities ranging from the very cheap to the very expensive and in various forms from raw through to toasted, although if you do buy it raw you will need to toast it before you eat it.

Some cheaper varieties, often from China will cost only .04 cents a sheet while from Japan’s Ariake Bay in Kyushu, Nori can cost up to .90 cents a sheet, and more!  The Japanese eat a lot of Nori and it is no coincidence, maybe, that their rates of obesity are ten times less than those seen in the USA.

How to eat Nori

Here are a few suggestions on how you can use Nori in your everyday diet:

  • Beans with Nori
    You can try adding Nori when you cook dried beans.  This will enhance the dish with vitamins and minerals as well as enhancing the flavour and making your beans easier to digest!
  • Nori as a snack
    Although Nori is barely there in weight, it can be surprisingly satisfying and is always nutritious.  It is a great choice to make as a take-to-work snack and a better choice than other salty snacks, to satisfy you.  The crispy texture makes it appealing to kids too.
  • Seaweed smoothies
    Using powdered Nori is a great way of sourcing natural protein, making it a favourite for a morning starter of a post work out replenisher.  Use a teaspoon of the powdered seaweed to add to your favourite smoothie and then adjust the amount you use, as you get accustomed to it.
  • A few seaweed flakes added to your meal
    Visit any health food stores or an Asian market and you will find a variety of products and seasonings that include seaweed. You could also make your own by combining ground or fine-chopped Nori, Dulse, Kombu, black pepper, sesame seeds and sea salt.
  • Stocks, soups and stews love Nori!
    Nori, or any seaweed is a great addition to savoury or more liquid foods.  Using a strip of Nori in veggie stock and then strain it out along with whatever other ingredients have been used.  You can also add it to a soup or a stew but it is best to take out the solid Nori strip before serving. Although, if you are making miso soup, it’s essential to leave the nori in as that’s what gives it that typical flavour.
  • Salad dressing, spiced up with seaweed
    Sprinkling some powdered Nori into a salad dressing is a great way to enhance the dressing.  Just allow it to sit for a few moments to absorb, before use.
  • Seaweed salad with Nori
    To make a delicious Nori salad, use it with sesame oil, spring onions, garlic, vinegar and oil along with salad vegetables.  Experiment with various veggies to see which combination you like best.
  • Nori sushi with rice and fish
    You don’t even have to make sushi yourself, you can easily buy it from a sushi takeaway restaurant or even from a supermarket. Fresh sushi is the best, of course, so avoid supermarkets if you can! If you prefer not to eat fish you can make vegan nori rolls at home.

sushi with nori

There are, of course, many other ways that you can eat and enjoy Nori (for example, with tofu and quinoa) but these ideas should get you started!


Nori is a great source of goodness as part of a healthy diet so yes, it is good for you, just be aware of its downsides.

We have tried to give you an accurate picture of the benefits and any possible drawbacks of Nori and we hope that the information in this article will help you to decide whether you would like to incorporate it into your diet.

Related content:
Kombu vs Nori

(1). Thyroid. 2004 Oct;14(10):836-41.
Variability of iodine content in common commercially available edible seaweeds.
Teas J1Pino SCritchley ABraverman LE.

(2). Food Chem Toxicol. 2003 Nov;41(11):1473-80.
Diets containing a high percentage of Nori or Konbu algae are well-accepted and efficiently utilised by growing rats but induce different degrees of histological changes in the liver and bowel.
Bocanegra A1Nieto ABlas BSánchez-Muniz FJ.

(3). Effects of seaweed supplementation on blood glucose concentration, lipid profile, and antioxidant enzyme activities in patients with type 2 diabetes mellitus
MS Kim, JY Kim, WH Choi… – Nutrition research and …, 2008 – synapse.koreamed.org
… 36. Urbano MG, Goni I. Bioavailability of nutrients in rats fed on edible seaweeds, nori
(porphyra tenera) and wakame (undaria pinnatifida), as a source of dietary fibre. Food
Chem 2002;76:281–286. 37. Warnick GR, Benderson J, Albers JJ …

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