Mozuku Seaweed Is a Longevity-Boosting Staple in Okinawa

It’s no secret that sea moss is overtaking every smoothie bar in town these days. TBH, we saw it coming last year, long before Hailey Bieber’s Strawberry Glaze Skin smoothie at Erewhon took TikTok by storm.

In an effort to stay up-to-date on one of our favorite oceanic food trends, we recently asked two registered dietitians about the science-backed health benefits of sea moss, and learned that all edible forms of algae can, in fact, offer gut and heart health benefits, help support a strong and healthy immune system, boost cognitive functioning, and fight inflammation. In short, consuming seaweed is a treat for both our taste buds and our bodies, and we should be consuming it in much more than just smoothie form.

However, as sea moss rapidly rises in popularity, we can’t help but wonder: What other nutrient-rich forms of sea greens should we be noshing on? When investigating some of the best seaweed sources around the globe, it was no surprise when we landed (figuratively) on the shores of Okinawa, Japan, known to be home to some of the longest-living people in the world. In the Blue Zone region of Okinawa, brown seaweed, otherwise known as mozuku, is an everyday staple in the centenarians’ diets. We spoke with an registered dietitian to learn more about mozuku, including its health benefits and how to incorporate it into meals.

What is mozuku seaweed, and what are its health benefits?

According to Lauren Manaker, MS, RDN, LD, CLEC, CPT, a registered dietitian based in Charleston, a few things set Okinawan seaweed, mozuku, apart from all of the rest. “If you have seen seaweed that is more brown than that classic green color many of us are accustomed to, then you may be feasting your eyes on mozuku—a nutrient-dense seaweed that offers unique health benefits,” Manaker says. While most forms of sushi seaweed and sheets of dried nori come from a species of red seaweed known as Pyropia (including P. yezonesis and P. tenera), Okinawan mozuku is derived from the genus Cladosiphon okamuranus.

According to Manaker, unlike green or red seaweed, brown seaweed is the only type that contains fucoidan, which is a naturally-occurring compound that boasts a bevy of health benefits. “Fucoidan has been shown to have antioxidant, anti-tumor, anti-coagulant, anti-thrombotic, anti-viral, and anti-inflammatory effects,” she says.

Although more studies are needed to analyze the health benefits of mozuku, Manaker says that preliminary data suggests that consuming this seaweed may offer heart health perks. Another study examined the anti-inflammatory effects of fucoidan in relation to the quality of life in advanced cancer patients, and found that proinflammatory cytokines were significantly reduced after two weeks of fucoidan ingestion.

So, does this mean we should start eating more brown seaweed? “Data shows that eating fucoidan, even in high quantities, is safe for generally healthy people,” Manaker says. “Nutrients may vary among different seaweeds. But generally speaking, seaweed is a natural source of iodine, a nutrient that helps support thyroid health. It is also a natural source of fiber, which can support gut health,” she adds. However, that’s not to say that it’s right for everyone. “If you have a thyroid disorder, it’s important to ask your health care provider if seaweed can be a part of your diet, as certain varieties may contain too much iodine for your needs.”

How do Okinawans commonly eat mozuku seaweed?

The brown algae is often harvested in the shallow, warm water off the coast of Okinawa by hand and then rinsed to remove any remnants of sand or hidden sea creatures. To preserve its health benefits, Okinawans typically eat mozuku raw, dressed with sweet vinegar, or paired with other gut-healthy ingredients like nattō, aka fermented soybeans; however, it can also be eaten deep-fried (as tempura) or in soups. The best way to get your hands on (literally) the freshest form of the seaweed would be to collect it yourself, but you can also find packaged mozuku at Japanese grocery stores or on Amazon, like this dried version.

Not only is mozuku a large part of the Okinawan diet, but it also is considered a “treasure under the sea” that’s an integral part of the local economy. According to the Okinawa Institute of Science and Technology (OIST) Graduate University, in 2006, the Japanese Cabinet Office estimated a 20,000-ton production, with an economic value of billions of Yen. However, within the last decade, rising sea temperatures have put the production of this valuable crop (and a source of income for many Okinawans) at stake. After all, 99 percent of this seaweed is produced in Okinawa and is almost entirely farmed by humans. This is why scientists are working endlessly to find the best ways to preserve this aquatic gem—one that’s a staple in the Okinawan diet.

Sushi on your mind? Same. Here’s what an RD would order on a hypothetical sushi date:

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