As you may have noticed, nori is the new potato chip. Or at least that’s how marketers are trying to position it. Slightly salty with a delicate crunch, snack-sized sheets of roasted nori have become popular munchies for adults and kids alike. These seaweed “crisps” are crowd pleasers not only because of the taste, texture and low calorie count, but because we figure that eating any kind of vegetable – even if it’s from the ocean – must be good for us. More and more parents are tossing those nifty seaweed snack-packs into school lunch boxes, relieved to have finally found something green that their children will eat.
But what do we really know about the benefits of eating seaweeds? Long a staple in Asian countries, most westerners are fairly new to the sea veggie scene. The popularity of seaweeds in the U.S. has been on the rise because they are indeed nutritious – and because recent studies point to health benefits ranging from weight loss to cancer prevention. Although it is decidedly a good move to add some seaweed to your dietary mix, there are a few things worth considering about the promise and safety of eating these marine greens, before you dive in.
There are thousands of kinds of seaweed, but only a small fraction are typically eaten. Members of the algae family, seaweeds are categorized into three varieties: brown, red and green. Brown seaweed, which includes kelp and wakame, is the most commonly consumed worldwide, followed closely by red. Red seaweed encompasses dulse and all types of nori, which holds our sushi rolls together and fills those snack-packs sold by Trader Joes, SeaSnax, and Marin County based GimMe Seaweed (owned by Annie Chun). Of the less popular green seaweeds, sea lettuces are among the variety most frequently eaten.
Seaweeds can be eaten fresh from the sea, but are more often dried and then roasted or reconstituted to their original form and incorporated into soups or salads. Just like the land-grown vegetables that we eat, seaweeds are cultivated and harvested commercially. Although harvested around the globe, China is responsible for nearly 60% of the world’s seaweed production. Much of the nori that is packaged and sold in the U.S. seems to be farmed in Korea, although more locally sourced seaweeds are sold by smaller companies such as Rising Tide Sea Vegetables, which hand-harvests wild seaweeds off the Mendocino Coast.
Fiber, Protein and Iodine Powerhouses
Seaweeds provide nutrients such as calcium and vitamins A, B-6 and C. Many seaweeds are also loaded with fiber and protein. But seaweed’s biggest claim to nutritional fame is that it is packed with iodine, a mineral that is essential for maintaining a healthy thyroid, which regulates our hormone levels.
Iodine deficiencies are on the rise among Americans because of our shift to natural sea salt rather than iodized salt, and can result in a wide range of problems including weight gain, depression and nausea. Getting enough iodine is particularly essential for pregnant women, helping to ensure healthy fetal development. Foods like baked potatoes, yogurt and cranberries are good sources of iodine, but none compare to the amounts found in most seaweeds.
But before you take the “more is more” approach, it’s important to note that you can overdo it. Too much iodine consumption can lead to problems very similar to iodine deficiency. Iodine levels can vary depending on where the seaweed is cultivated, and some seaweeds tend to contain much higher levels of iodine than others (kelp tends to be high, while nori is typically low).
The single serving of nori contained in a SeaSnax roasted seaweed snack-pack contains 25 mcg of iodine, which is “well within the safe zone,” according to Dr. Jane Teas, a prominent researcher at the University of South Carolina. The National Institutes of Health recommends no more than 1100 mcg maximum iodine intake for adults and 300 mcg for kids 4-8, while the minimum daily RDA is 150 mcg for adults and 90 mcg for 4-8 year-olds.
According to Teas, healthy Americans who don’t have iodine sensitivities shouldn’t worry about getting too much from eating any kind of seaweed in moderation. “For people in Japan, there seems to be some habituation to high iodine in their diet, and most people are not affected,” says Teas. She does caution that you can get too much iodine from taking seaweed capsules as a supplement, however.
The Promise of Prevention
Researchers have only just begun to uncover the medicinal properties of the unique chemical compounds found in seaweeds. Anecdotal evidence suggests that ancient Egyptians used seaweed to treat breast cancer, something scientists are studying today. A small proof of concept study conducted recently by Teas and her colleagues showed that seaweed may help regulate estrogen levels. Teas calls for future research to see if it may also contribute to reducing the risk of breast cancer and even helping reduce symptoms of PMS. In Japan, where breast cancer levels are particularly low, studies continue to point to seaweed as a major factor in this reduced rate, which was once attributed to increased soy consumption.
Seaweeds may help treat other types of cancer too. “In cell culture, seaweed has been shown to increase cancer cell mortality for several cancers, including colon and prostate cancer, melanoma, sarcoma and others,” says Teas.
It’s important to bear in mind that much more research is needed, but studies have also suggested that eating seaweed may help reduce inflammation, lower blood pressure and boost general heart health, among other benefits. Although clinical trials have not yet been conducted, a 2014 study found that seaweed consumption has the potential to reduce the amount of fat that our bodies absorb.
This is particularly promising news for those who remain unconvinced that they should swap their potato chips for toasted nori. Perhaps we can eat our seaweed and have our chips, too.
Mind Your Metals
Like their terrestrial counterparts, sea greens can be contaminated by heavy metals such as lead and mercury lurking in the environment where they are grown. Studies suggest that seaweeds harvested in certain regions tend to contain lower metal concentrations than others, and that certain seaweeds are more prone to absorbing various toxins. Hijiki, for example, has been shown to be particularly vulnerable to absorbing inorganic arsenic from seawater, while nori, kombu and wakame are not. Arsenic is a chemical often found in association with metals and has been linked to cancer.
Fortunately, the U.S. has strict regulations in place for making sure that the seaweeds we eat don’t contain unsafe levels of toxins. Look for packages stamped with the USDA certification mark or do a little research before you buy to help ensure that your seaweed will do you more good than harm.
Want more information? For a full rundown on seaweeds visit this reputable and comprehensive website created by the Irish Seaweed Research Group.