Nori Red Flags: Potential Downsides and Side Effects

Nori, the Japanese term for edible seaweed, has been a big part of East Asian diets for hundreds of years, mainly in Japan, Korea, and China. Nori is also known as ‘laver’ in the Western world – the dark green wrapper that all sushi lovers recognize. With the seaweed market valued at many billions of US dollars, seaweeds such as nori are gaining worldwide popularity. This tasty and salty snack has emerged as a healthy food that helps with weight loss and iodine deficiency. However, like many health foods, nori also comes with its downsides.

Nori provides an abundance of health benefits when you eat it in moderate amounts. However, excessive consumption and pre-existing medical complications can cause serious side effects.

Are you wondering about the health risks of seaweed like nori? Then, read on to find out all about the possible drawbacks and side effects of nori. 

1. Digestive Discomfort

Something good for one person might not be so good for someone else. For example, Nori is a food high in fiber content that can aid digestion. However, it can also cause some people tummy troubles. Having too much fiber often results in stomach problems such as gas, constipation, and bloating. Keep in mind that the recommended dietary fiber intake is 21-38 grams a day. Since each gram of fiber accumulates, overeating seaweed can cause you to cross the daily recommended dose of fiber. 

Our digestive systems often can’t digest the types of carbohydrates in seaweed. As a result, people prone to digestive issues or experiencing small intestinal bacterial overgrowth may encounter significant problems.

People who eat seaweed have sometimes complained about having abdominal pain, diarrhea, nausea, and bloating. But, you don’t have to worry if you make sure to eat nori in moderation! Severe side effects have been rarely reported.

2. High Iodine Content

A primary concern in eating too much nori is its high iodine content. The daily recommended intake of iodine is 140 micrograms. Overeating Nori can easily make you go over the recommended amount of iodine.

People who have thyroid-related health issues may discover that nori affects their thyroid function and medications. Those with any specific risk factors related to the thyroid should especially be aware that seaweeds like nori are saturated in iodine and take it in moderation. However, an average person can easily handle a high iodine level and will not experience any side effects. 

Some symptoms of iodine excess are weight gain, thyroid dysfunction, swelling, or tightness around the neck. 

3. High Sodium Content

Sodium is an essential element that helps maintain healthy blood pressure and keeps our nerves and muscles functioning correctly. The recommended dose of sodium is 2,300 milligrams per day. However, a typical American receives about 3,400 milligrams of sodium per day, often posing health risks.

Since it grows and absorbs salt from the sea, seaweed is always very high in salt levels. Although an average nori sheet provides 3 milligrams of sodium, nori sheets are often flavored with additional sodium. Additionally, your sodium content can easily exceed the limit if you eat nori with dishes spiced with soy sauce and salt.

Excessive sodium is known to increase high blood pressure and may eventually lead to heart failure, cirrhosis, and chronic kidney disease. So it’s always a smart idea to watch out for the sodium level in your meals, including your favorite dish with nori!

4. Pregnancy and Lactation

A healthy diet is crucial for both a pregnant mother and her baby. When you get pregnant, many foods you love are now out of bounds. Happily, seaweed lovers can still eat and benefit from some types of seaweed during pregnancy. Seaweed is high in iodine and can be beneficial to a pregnant mother—as long as she eats it in moderation.

Doctors recommend a daily iodine intake of 220 micrograms during pregnancy and 290 micrograms during breastfeeding. High levels of iodine in pregnancy can cause hypothyroidism in the baby, resulting in a goiter, which can interfere with breathing. Pregnant mothers should not take more than 500 mcg to 1100 mcg for an extended period.

Furthermore, a baby receives all the iodine it needs from the mother’s milk. This means that it’s vital for the mother to be getting enough iodine. On the other hand, excessive iodine in breast milk might cause thyroid dysfunction in the baby. Therefore, it’s always important to talk to your doctor if you have any breastfeeding questions.

Although iodine is necessary for both a mother and a baby, it’s always important to take it in the right amount. Snacks and recipes with seaweed often contain high sodium levels, so make sure to check the labels before trying out packaged seaweeds like nori.

5. Nori and Heavy Metals

Another common concern of nori involves heavy metals. Like a sponge, seaweed absorbs the minerals and chemicals around them in the seawater. If the seaweed is farmed in water containing toxins and metals, it will absorb them.

With that said, heavy metal content in nori is below the maximum concentration allowances in most countries. Furthermore, studies have shown that the metal concentration levels in seaweed do not cause any hazardous health risks.

However, it’s always best to consume seaweeds like nori at a moderate level to avoid any risks. Regular overconsumption of seaweed can cause toxic metals to pile up in your body over time, which can pose severe effects on your health.

Checking the source of your nori and choosing organic seaweed is always an excellent idea.

6. Drug Interaction

Some types of seaweed can interact with anti-thyroid and anticoagulant drugs, resulting in medical complications. Fortunately, the majority of medications do not pose a risk when consuming nori.

However, if you are undergoing treatment for hyperthyroidism, consuming iodine can cause abnormalities in the function of your thyroid gland. Similarly, the high content of Vitamin K in nori can interact with blood-thinning medications such as Warfarin. 

7. Source of DHA

Seafood products such as tuna, sardine, and salmon are rich in omega-3 fatty acids. Seaweeds like nori are an excellent plant-based source of omega-3 fatty acids. DHA is a type of omega-3 fatty acid that is helpful for brain, nerve, and vision health. However, DHA also lowers blood pressure. If you are suffering from low blood pressure or are already taking medication to lower your pressure, you might want to be extra careful to take nori in moderation.

8. Vitamin K Content

Nori could well be called the powerhouse of vitamins. Along with vitamins C, A, and B, nori is also a source of vitamin K. This vitamin allows blood to flow freely throughout the body and prevents arterial blood clotting. However, an excess of vitamin K can interact with anticoagulant drugs like Warfarin. The vitamin K content in nori might hamper the effectiveness of the medication and pose a risk of blood clots and stroke. If you are on any blood-thinning medicines, it’s always best to talk to your doctor before including nori in your diet.

9. Radioactivity

The fear of radioactivity has always been a problem for many people, especially after the Fukushima nuclear meltdown in 2011. Since Japan is one of the significant seaweed producers, there is a concern that nori harvested on Japanese coasts might be contaminated with radioactive exposure.

Does this mean that you have to give up on sushi and seafood completely? No, researchers do not advise restricting seaweed consumption due to possible radioactivity. Most nori producers perform radiation safety tests regularly and have stamps proving that contamination is under safety level. Nori from Fukushima has also passed the radiation safety tests and has begun shipments.  

Furthermore, seaweed is located at the bottom of the food chain, making it far less toxic than fish and other seafood.

Regularly consuming a moderate amount of seaweed and nori can protect against radioactivity. This is because of the high iodine and chlorophyll concentration in nori, a natural detoxifier that avoids and cleanses your body of radiation.

Anyhow, be cautious about the source of your nori, and you can enjoy it with complete peace of mind.

All in All

Seaweed, like nori, has quickly gained popularity as the new, healthy food trend in the Western world. It has seemed to escape from delicacy restaurants and made its way into everything from crackers to snacks, ice cream, and even seaweed pills. 

Nori is indeed a food rich in vitamins and nutrients that you can benefit from. However, it’s never a good idea to overdo anything, and it’s best to watch out for any health risks involved. Now that you know all about the dangers and disadvantages of nori, you can moderately implement it into your diet and benefit from this superfood.

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This article was co-authored by our team of writers and editors who share one thing in common: their passion for food and drinks!

JC Franco
Editor | + posts

JC Franco works as a New York-based editor at Foodrinke, driven by his lifelong love for food. His culinary journey began in childhood, as he eagerly assisted his mother with her local sandwich and bakery business, relishing every opportunity to sample her creations. Known among family and friends as an easy eater, JC has a particular affinity for Chinese, Italian, Mexican, and Peruvian cuisine. At Foodrinke, he channels his passion for food into his work, sharing his enthusiasm and knowledge with readers.