Eight types of seaweed from the Indian coast used in food, cosmetics, and medicine

Seaweeds growing along the Indian coast may be closer to the consumer than they seem. These algae can contribute to the creamy texture of ice cream, prevent ingredient separation in toothpaste, or even be included in medicinal preparations.

Despite rarely being noticed or having their names known, over 800 species of seaweed inhabit India's 7,500-kilometer coastline. Among them are red species attached to rocks near Tamil Nadu, and bright green ones found in shallow coastal waters. Approximately 60 of these species have commercial value, and some are already used in pharmaceuticals, cosmetics, the food industry, and laboratories.

For example, the smooth consistency of ice cream and the absence of ice crystals can partially be explained by carrageenan—a natural thickener and stabilizer derived from red seaweed. This same component helps distribute cocoa evenly in chocolate milk.

This is just one example. Three main seaweed extracts—carrageenan, agar, and alginate—form a global industry worth over half a billion dollars. According to a 2023 World Bank report, it is projected that 10 developing seaweed markets could reach a volume of $11.8 billion by 2030.

The appeal of seaweed is also due to how it is cultivated: it does not require agricultural land, freshwater, fertilizers, or pesticides, which is particularly relevant against the backdrop of increasing pressure on land and water resources.

Below are eight seaweeds found on the Indian coast and their surprising applications, ranging from 'green caviar' to toothpaste, snacks, and medicines.

1. Kappaphycus alvarezii: In chocolate milk and ice cream

This species is found on the coast of Tamil Nadu, specifically on the islands of Rameshwaram and Pamban. At low tide in the shallow waters near Rameshwaram, one can see rope-like structures between wooden poles, on which thick, rubbery red-purple branches are attached. This is Kappaphycus alvarezii, an alga that produces carrageenan—one of the most common natural additives in the food industry.

Carrageenan is obtained by boiling and processing dried seaweed. The result is a gelling agent used in ice cream to prevent the formation of ice crystals and in chocolate milk to ensure even distribution of cocoa instead of settling at the bottom. The global trade in carrageenan is estimated at approximately $240 million.

2. Gracilaria: Source of agar

This species is found in Tamil Nadu, Gujarat, and Andhra Pradesh. Gracilaria is a primary source of agar—a transparent, odorless gelling substance known as Chinese grass, widely used in desserts and jellies across South Asia.

However, agar plays a more significant role in science. Microbiological laboratories worldwide use agar plates—flat dishes with nutrient-rich gel where bacteria and fungi can be cultured and studied. Furthermore, Gracilaria can be consumed in another form. Fibers from Gracilaria edulis contain up to 96% dietary fiber; they are colorless, odorless, and highly functional. Researchers are studying the possibility of using this fiber in products such as sausages and noodles to increase their fiber content. The global agar market is valued at approximately $132 million.

3. Gelidiella acerosa: A laboratory necessity

Gelidiella grows alongside Gracilaria on the open rocky coasts of Tamil Nadu, Kerala, and Karnataka, forming dense, tough mats firmly attached to rocks. Like Gracilaria, it yields agar. The difference lies in the purity and strength of the agar. Agar from Gelidiella is particularly suitable for biotechnological and pharmaceutical applications. Research institutes, diagnostic companies, and drug manufacturers value it for these specialized needs. Gelidiella also contributes to research on seaweed-based bioplastics. Such materials can be biodegradable and renewable alternatives to petroleum-based plastics, with the potential for lower production costs.

4. Sargassum: From sea to rice and corn snacks

Sargassum is one of India's most common brown seaweeds, recognizable by its olive-brown color, leaf-like branches, and tiny air bubbles that provide buoyancy. On land, it is processed into biofertilizers, used as livestock feed supplements, and studied as a source of biofuel and biodegradable materials. Sargassum is also incorporated as a powder into rice and corn extruded snacks, adding macro- and micronutrients without significantly altering the taste.

5. Hypnea: What's in your toothpaste?

Hypnea is a thin, highly branched red seaweed found in tropical coastal waters. Similar to Kappaphycus, it can serve as a source of carrageenan. This means that extracts from this seaweed can be used in chocolate milk, ice cream, processed foods, toothpaste, cosmetics, and pharmaceutical formulations. They help prevent ingredient separation, extend shelf life, and create a stable texture, acting as a substitute for some synthetic additives. As consumer demand shifts towards natural ingredients on product labels, the commercial significance of Hypnea continues to grow.

6. Turbinaria: Medicines from rocky reefs

Turbinaria is a tough, resilient brown seaweed with rigid fan-shaped leaves, strong enough to remain attached even when hit hard by waves against rocky reefs. It has been used in pharmaceuticals, including formulations investigated for inflammatory pain and arthritis. Its effectiveness has been evaluated compared to standard non-steroidal anti-inflammatory drugs in animal models. According to the Indian Council of Agricultural Research (ICAR), one such product is available in the form of 350 mg plant capsules suitable for vegetarians, and no side effects have been reported to date.

7. Ulva (sea lettuce): Nutrient-rich green

Ulva is a bright, thin, translucent, and leafy seaweed that grows in the intertidal zones along the entire Indian coast. Nutritionally, it is rich in beneficial compounds, including vitamins A, C, and B complex, calcium, iron, dietary fiber, and protein. Globally, it is attracting growing interest as a sustainable food ingredient. In India, researchers process it into a powder that can enrich plant-based products with protein and fiber, such as vegetable patties.

8. Caulerpa (sea grapes): 'Green caviar' and cookies from Indian reefs

Caulerpa grows in clusters of tiny greenish beads that strikingly resemble miniature bunches of grapes. It is eaten fresh in salads in various Asian coastal cultures, and in other places, it is sold as 'sea grapes' or 'green caviar.' Indian scientists have developed cookies using Caulerpa racemosa as a functional food ingredient, based on its high protein, fiber, and antioxidant potential. This product is already commercialized by two companies from Kerala and is sold as organic cookies aimed at supporting digestion.