Yes, seaweed can be nutritious, but is it fattening?

Few foods are as lauded by nutritionists as seaweed. A food and medicine source that the U.S. National Ocean Service notes was used for millennia by ancient Roman and Egyptian civilizations, seaweed is now frequently touted and recommended by wellness influencers, doctors, and dieticians across social media and in healthcare settings. 
Its unique nutritional benefits and medicinal properties have helped seaweed soar in popularity in recent decades, causing the global commercial seaweed market to reach more than 17 billion last year, per one analysis. 
While there are circumstances when overconsumption can become problematic, nutritionists say the food’s popularity is generally a good thing, and that it has many health advantages, including being potentially beneficial for healthy weight management. 
Similar to most land-based plant life that humans consume, seaweed can vary greatly in shape and size but consists of plants grown across the world’s oceans. “It’s made from sea vegetables that can be eaten and used for culinary purposes,” explains LeeAnn Weintraub, a registered dietician and nutrition consultant based in Los Angeles.  
Most commercial seaweed is grown and cultivated in seaweed farms, with many varieties being ready to harvest in as little as 6 to 8 weeks. Seaweed is often large and leafy, and comes in hundreds of colorful varieties including dulse, hijiki, wakame, red algae, and kombu. 
Nori is one of the most popular seaweed varieties that’s also called laver seaweed and is known for its crispy texture. It’s made from red algae that’s been cleaned and dried, then blended into a mixture before being dried again in flat sheets. It’s often seasoned and used as a substitute for tortillas, cut into chips, or rolled to wrap fish and rice to make sushi. 
This popular form of seaweed “is commonly found in Asian cuisine, particularly Japanese recipes,” says Weintraub. “It is used in miso soup, sushi rolls, seaweed salads, poke bowls, and seaweed snacks, among other foods.”
No matter how you enjoy it, seaweed is full of health benefits. Just 26 grams of Nori seaweed, for instance, packs 1.5 grams of protein, 92 milligrams of potassium, 18 milligrams of calcium, 15 milligrams of phosphorus, and 10 milligrams of vitamin C, per the U.S. Department of Agriculture. It also contains iron, magnesium, zinc, copper, riboflavin, vitamin B6, folate, vitamin A, vitamin E, and a single serving of seaweed offers a fifth of the recommended intake of vitamin K one needs each day. 
Seaweed if also a great source of fiber to promote gut health, antioxidants to prevent or delay cell damage, and may also be helpful in reducing inflammation and one’s risk of colon cancer.
“Seaweed is rich in many vitamins and contains many minerals as well,” says Weintraub. “Because of such nutrients, seaweed is a very healthy snack option.” 
Amy Goodson, a nutritionist and registered dietitian at The Sports Nutrition Playbook, agrees, but says that when consumed in very high amounts, “some seaweeds can accumulate heavy metals or other contaminants from the ocean, so it’s essential to choose reputable sources and consume it in moderation.”
She adds that some people may be sensitive to the high iodine content in certain types of seaweed, “so those with thyroid conditions should exercise caution and consult with a healthcare professional.”
Another benefit provided by seaweed is that it can be helpful in healthy weight management. Many varieties are very low in fat, and seaweed’s high-fiber content – a 5-gram serving of brown algae has nearly 15% of one’s daily recommended amount – not only helps prevent digestive issues but can also leave one feeling fuller for longer. This can help with appetite control and satiety. 
“Seaweed is also low in sugar and calories,” says Caroline Susie, a registered dietician and national spokesperson for the Academy of Nutrition and Dietetics. Indeed, 10 sheets of Nori seaweed contain just 9 calories and about tenth a gram of sugar.   
“All this makes seaweed a good choice for those watching their weight,” says Goodson. “Additionally, seaweed’s nutrient density means you get a lot of nutritional bang for your buck – making it a valuable addition to a balanced diet.”