Seaweeds are really algae that live in the sea although some species of green algae live in fresh water or on land. They are benthic organisms, which means that they spend their lives attached to the sea floor. There are 10,000 species of marine algae and about 6,000 are red algae; the other two types are brown algae and green algae.
The Asian countries, especially Japan, Korea, and China, are the largest producers of seaweed for direct human consumption. Found in everything from soup to sushi, seaweed is a major part of the Asian diet. Although nutritious, seaweed has not caught on as a major food source in Western countries, usually eaten only by health food enthusiasts. The exception is a seaweed found in Wales called aver, which is baked into a popular bread called averbread. Seaweed is a good source of protein and several minerals and antioxidant vitamins, but is also very high in sodium.
While seaweed is packed with beneficial nutrients and therefore a good thing to add to our diets, there have also been many scientifically unfounded claims made about its healing properties. It is used widely in traditional Chinese and Japanese medicine, touted as healing everything from cancer to impotence. According to the National Institutes of Health, however, because of the lack of data on human subjects, seaweed supplements rate only a grade of "C" for the following properties claimed by manufacturers: antibacterial/antifungal, anticoagulant, antioxidant, cancer, diabetes, goiter and weight loss.
Several substances extracted from seaweed are used throughout the cosmetic and personal care industries. Alginates, carageenanand agars are found in many products, including toothpaste, face creams, soaps, and shampoos. These substances not only act as fillers, but are purported to have beneficial effects on the skin and hair.
According to the Food and Agriculture Organization of the United Nations (FAO), products made from seaweed are a nearly $6 billion industry worldwide, with cultivation for food making up the majority at $5 billion. The rest of the market is for extracts used in fertilizers, animal feeds, cosmetics and thickeners for a variety of food and other products. The newest use for seaweed is as a possible alternative source of fuel to reduce our reliance on fossil fuels.