European researchers have been working to investigate whether seaweed could be a good substitute for salt.

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People in Japan have a longer life expectancy and a significantly lower risk of several serious diseases compared to Americans, including cancer and heart disease._[1,2] Extensive research has looked at differences in the Japanese diet compared to the typical Western diet. Much of the interest has been on higher fish and soy consumption, but recently the focus has shifted towards seaweed.

A Nutritious Marine Food

Seaweed is a nutrient-dense, low-calorie food. It is extremely high in protein and dietary fiber, and it is a rich source of vitamins, minerals, and other nutrients, including magnesium, iron, iodine, calcium, antioxidants, folate, vitamin B, vitamin E, omega 3 fatty acids, and essential amino acids._[1,3-5] Sea greens often contain higher amounts of essential nutrients than land-based plants or animal products. For example, wakame and sea spaghetti, two types of brown seaweed, can have eight times more calcium than milk._[3]

Seaweed has a very low total fat content, but it is remarkably high in polyunsaturated fats, specifically omega-3 fatty acids. It is a rich source of DHA, EPA, and ALA. It is low in omega-6 fatty acids, making a favorable omega 6:omega 3 ratio, which has positive health effects._[6]

This marine superfood is also high in antioxidants.7 Brown seaweeds are particularly rich in fucoidan and fucoxantin, carotenoids that protect cells from damage; fight cancer; modulate blood glucose and insulin; reduce inflammation; and lower cholesterol, triglycerides, and blood pressure._[4,8]

Adding seaweed to your diet can also help to protect from toxins and detoxify, as compounds extracted from seaweed chelate heavy metals and toxins, eliminating them from your body._[8]

Seaweed is an Iodine-Rich Food

Seaweed is an iodine powerhouse. Iodine is essential in the body for thyroid hormone synthesis and it also has antioxidant and anticancer activities._[9] Eating seaweed is a great way to boost your iodine intake to sufficient levels if you are deficient in this vital nutrient. Women with insufficient levels of iodine who supplemented with seaweed found marked improvements in their iodine levels without any adverse effects on their thyroid health._[10]

But be cautious with seaweed intake if you have a thyroid disorder. Boosting your iodine intake above the recommended range can cause health problems. Nori, one of the most popular types of seaweed, is lower in iodine than some other seaweed varieties, like kombu. If you already have high iodine levels, nori might be a good option.

Widespread Health Benefits

Cardiovascular disease. Seaweed has anti-inflammatory effects, prevents coagulation, and more. Some studies in humans have found beneficial effects such as lowered blood pressure, waist circumference, and cholesterol in people supplementing with various types of seaweed._[1]

Weight loss. Seaweed, which is high in dietary fiber, may aid in weight loss, although more human trials are needed to confirm preliminary results._[1]
Brain health. Seaweed extracts fight inflammation in the brain, inhibit neuronal cell death, and protect against neurotoxicity. These effects may help to protect the brain from degeneration and various conditions._[11]

Depression. In one study on 1,745 pregnant women in Japan, those who consumed the most seaweed had the lowest rates of depressive symptoms._[12]

Cancer. Seaweed is thought to contribute to the remarkably low rates of cancer in Japan and other Asian countries. There is a large body of laboratory evidence showing the anticancer properties of seaweed, especially in breast and colorectal cancer cells. It can inhibit cancer cell growth, proliferation, and metastasis, and promote cancer call apoptosis (cell death)._[13] Compounds in seaweed also can reduce the activity of estrogen, which may help protect against estrogen-dependent cancers like breast cancer._[14]

Diabetes. High levels of antioxidants and fiber in seaweed help to control blood sugar and treat type 2 diabetes. Seaweed supplementation in people with type 2 diabetes is related to lower blood glucose and insulin levels, as well as improved lipid levels, like lower triglycerides and higher HDL cholesterol._[1,15-17]

Bone health. Rich in calcium and magnesium, seaweed may promote healthy bones. In people with knee osteoarthritis, supplementation with 275 mg Aquamin (a seaweed product) showed improved symptoms and decreased the need for NSAID treatment._[18]

Buying Seaweed: Safety Concerns

Seaweed absorbs nutrients and compounds from the water it grows in. This quality that helps make it so nutritious can also make it a source of dangerous toxins. If grown in contaminated water, seaweed will absorb toxins like heavy metals.10 For this reason, make sure to choose seaweeds with an organic certification; this kind of seaweed must be grown in clean waters and should not contain any heavy metal toxins.

Keep in mind that while seaweed is a healthy food that can be a fun new addition to your diet, there does exist too much of a good thing. Overdoing it with your seaweed intake may put you at risk for thyroid disorders associated with excess iodine.

Most natural grocery stores have a variety of seaweed options to experiment with and larger grocery chains often have a few selections in the Asian foods section. Nori, which is used to make sushi, is generally easy to find. Seaweed can come fresh, dried, or prepared into specific food items. Experiment with different varieties of seaweed to find what you like best.

This article was originally published in 2016. It is regularly updated.

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