Sea Greens 101: Types, Benefits, Where to Buy Them, and More

A review of research in the Journal of Applied Phycology

points out that sea vegetables are a good source of the ever-important B vitamins, as well as vitamin A and vitamin E. Vitamin A is crucial for vision and your immune system, according to the National Institutes of Health (NIH )

and vitamin E is essential for everything from your blood to your brain to your skin.

Kelp, for example, contains 70 micrograms (mcg) of beta-carotene in 100 grams (g), or about ¾ cup (and your body converts beta-carotene into vitamin A), according to the U.S. Department of Agriculture (USDA).

You’ll also get 1.3 g of fiber, 89 milligrams (mg) of potassium, and 168 mg of calcium.

Wakame, meanwhile, contains 216 mcg of beta-carotene in about ¾ cup, along with 1 mg of vitamin E, 150 mg of calcium, and 107 mg of magnesium.

And a type of seaweed called agar has small amounts of vitamin B6 (0.03 mg) in about ¾ cup, plus 226 mg of potassium and 54 mg of calcium.

A word of warning, though: “Be careful not to consume too much iodine from algae,” says Retelny. According to the NIH, too much iodine can affect your thyroid function, leading to a variety of problems, including hypothyroidism. In most cases, it’s hard to exceed the upper limit of 1,100 mcg per day from foods and supplements, but two tablespoons (tbsp) of dried flaked nori, for example, provides more 100mcg.

What’s more, seaweed may also contain beneficial dietary fibers called polysaccharides, according to a study published in Marine Drugs.

These fibers can function as prebiotics to potentially help maintain a person’s gut bacteria, which benefits health and well-being, the researchers note. “The health benefits of seaweed also appear to be related to constipation and improving bowel regularity,” says Dr. Agarwal.

Another advantage? You’ll also be full of beneficial omega-3 fatty acids. One study (done in the lab) found that red and brown algae could be a valuable source of fatty acids, including omega-3s. Eaten on their own or used as an ingredient in dietary supplements and other products, these green vegetables could be an excellent vegan source of these healthy fats.

Omega-3s are essential fatty acids that help everything from your heart to your immune system and lungs work their best.

Additionally, published research Antioxidants

found that adding brown algae to rye snacks increased the antioxidant levels of the snacks. The researchers note that this shows that seaweed can potentially be used as a natural ingredient to improve consumer health. (As a reminder, antioxidants are natural substances that can delay — even prevent — cell damage in the body, according to the NIH.)