Edible seaweeds are types of algae that can be eaten raw or cooked and consumed with other foods, such as in sushi. Seaweeds have been used as a food source in Japan, Korea and China for thousands of years. Seaweeds are a rich source of many nutrients, especially iodine, which is why some people call them "super-foods." Not all seaweeds should be eaten, as some are toxic and others contain compounds that cause gastrointestinal distress.
Types of Seaweeds
Edible seaweeds are multi-cellular algae, usually classified as either red, green or brown varieties. Most edible seaweed is of marine origin, whereas freshwater seaweeds are usually toxic for human beings. Seaweeds are also called sea vegetables by some cultures, and are now widely eaten in countries outside of Asia, such as Ireland, Iceland, France, Norway, eastern Canada and New Zealand. Kelp is perhaps the best known seaweed in Western countries, but other popular varieties include nori, spirulina, chlorella, arame, wakame and sea lettuce.
Nutrients in Seaweeds
Seaweeds are rich in many vitamins, especially B-vitamins and folic acid, but also vitamins C and E. Seaweeds are also excellent sources of minerals, such as magnesium, calcium and boron, and good sources of iron and phosphorus according to the "American Dietetic Association Complete Food and Nutrition Guide." Chlorophyll, which is the compound plants use to convert the sun's radiation into energy, is also present in seaweeds in large amounts. However, the nutrients that are most abundant in seaweeds are sodium alginate and iodine, which are compounds effective at shielding the body from the negative effects of radiation.
Benefits of Eating Seaweeds
Sodium alginate protects the body from radiation by reducing radioactive strontium absorption in the intestines, binding it with calcium and then excreting it from the body, as cited in "Medical Nutrition and Disease." Iodine protects the thyroid gland from the effects of radiation and is essential for the production of thyroid hormones, which govern metabolism. Chlorophyll contains antioxidants and amino acids and is able to stimulate red blood cell production in bone marrow, which is further aided by seaweed's high iron content. Vitamins C and E are strong antioxidants, which reduce inflammatory reactions, scavenge free radicals and protect blood vessels. The abundant minerals in seaweed, particularly kelp, are important for strong bones and normal muscle function. Chlorella has the additional ability of removing toxic substances, such as cadmium, dioxins and PCBs, from the body by binding to them. Further, chlorella detoxifies uranium, lead, mercury and copper.
Some Cautions
Marine algae are not considered toxic to human beings, but some do contain acids that irritate the stomach and intestines, while others can produce strong laxative effects that can lead to dehydration and electrolyte imbalances. While iodine is essential to the thyroid, consuming high levels of seaweed can produce sickness from too much iodine. According to "Human Biochemistry and Disease," thyroid specialists usually suggest about 150mcg of iodine daily, which is well below levels that cause negative side effects.
References
- "American Dietetic Association Complete Food and Nutrition Guide"; American Dietetic Association; 2006
- "Medical Nutrition and Disease: A Case-based Approach"; Lisa Hark; 2008
- "Human Biochemistry and Disease"; Gerald Litwack; 2008
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