In the U.S., seaweed may be most recognized as the green wrapping around sushi rolls, but in Japan and many other Asian countries, sea vegetables are a dietary staple. Also known as edible seaweed, as some forms of seaweed are inedible or contain natural toxins, a variety of these nutrition-packed vegetables are available at specialty and Asian markets -- with names such as nori, kelp, dulse, kombu, arame and hijiki. Potential health benefits of edible seaweed are many, including weight loss, blood sugar improvements, heart disease and cancer risk reduction, enhanced immunity and digestive health.
Weight and Blood Sugars
Sea vegetables are not only low in calories, but a good source of fiber -- which increases fullness and curbs appetite. While a lower calorie, high fiber diet helps with weight loss and blood sugar control, certain components in edible seaweed may provide additional benefits. For example, fucoxanthin, the pigment found in brown seaweed, has been linked to enhanced fat burning in animal studies, according to an October 2011 article in “Marine Drugs.” Alginate, a fiber found in kelp, forms a gel when mixed with fluids in the gut, which slows stomach emptying, increases fullness and causes blood sugar to rise more slowly after meals. In addition, a study reviewed in the March 2014 issue of “Food Chemistry” linked alginate with lower activity of pancreatic lipase -- an enzyme that helps digest fat, suggesting this fiber may reduce the calories absorbed from fat.
Diets that emphasize edible seaweed are linked to a lower risk of heart disease. The Japanese dietary pattern in particular, which is rich in soybeans, fish, vegetables, seaweed and green tea, is associated with a reduced risk of cardiovascular disease, according to a study published in the June 2007 issue of “International Journal of Epidemiology.” According to animal research published in the February 2014 issue of “Nutrition Reviews,” sea vegetables have anti-inflammatory, antioxidant and blood thinning properties -- all of which can reduce cardiovascular risk. The authors of this review also suggested the lower heart disease risk is related to seaweed’s omega-3 fatty acid content, and the cholesterol-lowering properties of seaweed’s fiber content.
Populations that regularly consume sea vegetables have lower rates of cancer, according to the article in “Nutrition Reviews.” In addition to the antioxidant effects of seaweed, fucoxanthin has been shown to have an inhibitory effect on tumor cells, according to laboratory research summarized in the “Marine Drugs" review. A diet rich in sea vegetables is also linked to lower estrogen levels in women, which can decrease breast cancer risk, according to a March 2009 article in “American Institute of Nutrition.” However, limited human research is available on the role of seaweed in cancer prevention and treatment.
The fiber and other carbohydrates in seaweed serve as prebiotics, or the fuel for the healthy gut bacteria. Sea vegetables are also beneficial to gut health because their fiber content assists with normal bowel movements. In addition, seaweed is touted to have antiviral properties, and to provide benefits to bone and eye health. However, most of the research on the health benefits of seaweed has not been completed on humans. Since seaweed contains certain compounds not found in terrestrial or land plants, more research is needed to more clearly understand the role of these vegetables in human health.
According to a June 2016 article in “Today’s Dietitian,” seaweed possesses blood thinning and immune-stimulating properties. If you take blood thinners, immunosuppressive medications or have an autoimmune disorder, seek your doctor’s advice before deliberately increasing seaweed in your diet. Sea vegetables are also rich in iodine and can be very high in potassium -- both typically beneficial nutrients. However too much iodine may be problematic in certain thyroid disorders, and excessive potassium in a person with severe kidney disease can cause life threatening heartbeat irregularities. If you have any health conditions, talk to your doctor before significantly increasing seaweed in your diet.
Reviewed and revised by: Kay Peck, MPH RD