Health Benefits
“Seaweed, a sea algae, is high in minerals and vitamins including iodine, copper, calcium, magnesium, manganese, vitamin B2, and vitamin C,” says Lisa Dreher, a registered dietician with the UltraWellness Center in Lenox, Massachusetts. “It’s also one of the few food sources of the less well-known mineral vanadium. Preliminary research shows that vanadium may improve the body’s sensitivity to insulin and decrease the body’s production of glucose.” Moreover, Dreher notes that seaweed contains unique phytonutrients and antioxidants needed to protect cells and DNA against damage. “Plus, it favorably alters estrogen and phytoestrogen metabolism, meaning if eaten in moderate amounts over time, it can be protective in women at risk of estrogen-sensitive breast cancers,” she says.
Three Different Types of Seaweed
“Seaweeds are categorized based on their coloring, cell structure, and other traits,” says Tammy Lakatos Shames and Lyssie Lakatos, both registered dieticians and founders of The Nutrition Twins. “Red algae/seaweed is in nori and is the seaweed used in sushi; brown algae is known as seaweeds like kombu and kelp, and is used in miso soup; green algae is found in sea lettuce and sea grapes.” According to Dreher, brown seaweed tends to accumulate more iodine than other sea vegetables and can range anywhere from 110 to 1,500 micrograms of iodine per gram." But whether you eat nori, dulse, a blue-green alga like spirulina, or something else, every seaweed offers its own unique set of nutritional perks, making them all worthy dietary additions for most people.
Seaweed Isn’t Great for Everyone
While seaweed is said to benefit people with hypothyroidism, it’s not a great idea in abundance for people with hyperthyroidism. “Eating too many iodine-rich foods can worsen hyperthyroidism, so if you have it, you should avoid seaweed, as well as sushi rolls that are wrapped in seaweed,” says Shames and Lakatos. “Further, if you’re on any blood thinners, check with your doctor before eating seaweed because it’s rich in vitamin K, and blood thinners often work by interfering with the actions of vitamin K. Typically, if you increase the amount of vitamin K in your diet, you also need to increase your medication.” Dreher also notes that excess amounts of polysaccharides (carbohydrates) found in seaweed, which feed the bacteria in our gut, may contribute to gas, bloating, and gut discomfort in certain individuals, especially those with small intestinal bacterial overgrowth. “While the benefits outweigh the risks of eating seaweed in these situations, it’s important to start with a small amount and then adjust based on how you feel.”
How Much Seaweed is Safe to Eat?
For healthy individuals without a thyroid condition, the recommended daily allowance for adults 19 years and older is 150 micrograms and the upper limit is 1,100 micrograms, according to Dreher. “All seaweed varies as far as its iodine content. One dried sheet (1 gram) can contain anywhere from 11 to 1,989 percent of the RDA for iodine,” she says. Dreher singles out the average iodine content of three common seaweeds to elucidate the disparity:
Nori contains 37 mcg iodine per gramWakame contains 139 mcg iodine per gramKombu contains 2,523 mcg iodine per gram
Quality Matters
“Seaweed can act like a sponge, easily absorbing heavy metals such as arsenic, lead, mercury and cadmium,” Dreher says. “Although trace amounts of arsenic are present in a lot of seaweed, these heavy metals can be much more concentrated in seaweed grown in water polluted by industrial waste as well as those that aren’t organic.” Dreher strongly recommends always opting for organic seaweed from companies that are dedicated to producing products in clean waters, such as the Gulf of Maine and the North Atlantic.
Easy Ways to Add Seaweed to Your Diet
Mary’s Gone Crackers and SeaSnax are the two most popular nutritionist-approved seaweed snacks, but you can also opt for miso soup packed with kombu, or seaweed flakes, which can be added to roasted veggies and salads. (Many store-bought seaweed snacks are also very high in sodium, so be sure to check the labels.) Another option is to add powdered spirulina, a type of seaweed that’s rich in protein, to your favorite smoothie recipe, says Nealy Fischer, founder of The Flexible Chef. “Seaweed wraps are also a great idea because they’re basically a veggie-packed wrap without the carb-heavy exterior,” says Fischer. “Start by simply julienning whatever veggies you have on hand (think carrots, cucumber, mushrooms) then place them in a full-size nori sheet and roll everything like you would a wrap. Serve with a miso dressing for dipping.” For something more filling, Fischer suggests raw kelp pad Thai. “Soak one package of kelp noodles in water until they become soft and mix with your favorite pad Thai sauce until evenly coated. Serve with fresh cilantro, red pepper flakes, and other desired toppings,” she says. You can bulk this dish up with your lean protein option of choice and an unlimited amount of non-starchy vegetables for a belly-filling, healthy meal.
