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Seaweed: Food from Underwater

by Admin-Phmp
Published: Last Updated on

Text and Photos by Henrylito D. Tacio

The Philippines, with a total coastline of 36,289 kilometers, has marine resources that provide food to millions of Filipinos. One of these is seaweeds, those marine plants that grow abundantly in shallow reef flats and in lagoons with a water depth of fewer than two meters at high tide.

Globally there are over 9,000 species of seaweed divided into three major types: green, brown, and red. Red is the most species-rich group (6,000), followed by brown (2,000) and finally green (1,200).

The Philippines is home to various kinds of seaweeds, of which 390 species have been identified as having economic value as food, animal feeds, fertilizers, diet supplement, medicines, and raw materials for industrial products.

Seaweed draws an extraordinary wealth of mineral elements from the sea that can account for up to 36% of its dry mass, according to Dr. Subhuti Dharmananda, director of the Institute for Traditional Medicine at Portland, Oregon.

What’s in seaweed? Nutrition experts classified seaweed as one of the richest plant sources of calcium. Its calcium content is typically about 4-7% of dry matter. At 7% calcium, one gram of dried seaweed provides 70 milligrams of calcium, compared to a daily dietary requirement of about 1,000 milligrams. Still, this is higher than a serving of most non-milk based foods.


Protein content in seaweed varies somewhat. It is low in brown algae at 5-11% of dry matter but comparable in quantitative terms to legumes at 30-40% of dry matter in some species of red algae. Green algae also have significant protein content, that is, up to 20% of dry matter. Spirulina, a micro-alga, is well known for its very high content: 70% of dry matter.

Seaweed contains several vitamins. Red and brown algae are rich in carotenes and are used, in fact, as a source of natural mixed carotenes for dietary supplements. The content ranges from 20-170 parts per million. The vitamin C in red and brown algae is also notable, with contents ranging from 500-3000 parts per million. Other vitamins are also present, including B12, which is not found in most land plants.

Dr. Dharmananda claims seaweed has very little fat, ranging from 1-5% of dry matter, “although seaweed lipids have a higher proportion of essential fatty acids than land plants.” Green algae, whose fatty acid make-up is the closest to higher plants, have a much higher oleic and alpha-linolenic acid content.

Seaweed has high fiber content, making up 32% to 50% of dry matter. The soluble fiber fraction accounts for 51-56% of total fibers in green and red algae and 67-87% in brown algae. Soluble fibers are generally associated with having cholesterol-lowering and hypoglycemic effects.

Wikipedia reports that as food, seaweeds are consumed by coastal people, particularly in East Asia (Japan, China, Korea, Taiwan, Thailand, Cambodia, and Vietnam), and those living in Indonesia, Belize, Peru, Chile, Scandinavia, Ireland, Wales, the Philippines, and Scotland.

In Asia, seaweed is a popular ingredient in some recipes. China’s zicai, Korea’s gim, and Japan’s nori is actually sheets of dried Porphyra species used in soups or wrap sushiChondrus crispus (commonly known as Irish moss or carrageenan moss) is a red alga used in producing various food additives. Affectionately called dulce in northern Belize, seaweeds are mixed with milk, nutmeg, cinnamon, and vanilla to make a standard beverage.


There are about 60 varieties of seaweeds in the Philippines that are considered edible. These are gulamang dagat, gamet, pocpoclo, culot, lato, guso, barls-barls, bulaklak bato, and balbalolang. Some of these varieties can be processed into jams, jellies, candies, pickles, babies’ food, and gulaman bars.

In Tiwi, Albay, residents discovered a new pansit or noodles made from seaweed, which has health benefits. Seaweed noodles can be cooked into pansit canton, pansit luglug, or spaghetti.

Unknown to many, seaweeds possess some medicinal values. They are used to treat or prevent goiter, glandular troubles, stomach disorders, intestinal and bladder difficulties, unusually profuse menstrual flow, high blood pressure, and high plasma-cholesterol level. 

The Gracilaria species are used locally as pain relievers and ointments. It has been asserted that seaweeds may have curative properties for tuberculosis, arthritis, colds, influenza (or flu), worm infestations, and even tumors. Currently, a number of research studies have been conducted to investigate these claims and other effects of seaweed on human health.

Some studies have found that seaweed can promote weight loss. For this reason, seaweed extract is used in some diet pills.

Commercially, seaweeds are valued for their colloids or gluey substance, particularly agar, carrageenan, and alginate. Both agar and carrageenan are extracted from red seaweeds, while alginate is extracted from brown seaweeds.

Agar is used in making jellied desserts, as a stabilizer in pie fillings, piping gels, icings, cookies, cream shells, and as a thickening and gelling agent in poultry, fish, and meat canning. In the medical and pharmaceutical industries, agar serves as a laxative, suspending agent for barium sulfate in radiology, ingredient for slow-release capsules and in suppositories and surgical lubricants, and as a disintegrating agent in tablets. It is also used as impression materials to make accurate casts in prosthetic dentistry, criminology, and tool manufacturing.

On the other hand, Carrageenan is used in making ointments, as an emulsifying agent in water-insoluble drugs and herbicides, and as a texturing agent in toothpaste and powder. It is also used in salad dressings and sauces, dietetic foods, and as a preservative in meat and fish products, dairy items, and baked goods.

Alginates enjoy many of the same uses as carrageenan but are also used in the production of industrial products such as paper coatings, adhesives, dyes, gels, explosives, and in processes such as paper sizing, textile printing, hydro-mulching, and drilling. In the biomedicine and pharmaceutical industries, alginates are used in wound dressings and production of dental molds and have a host of other applications.

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