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High iron content and bioavailability in humans from four species of marine algae
Identifier
016982
Type of Spiritual Experience
Background
The sea lettuces comprise the genus Ulva, a group of edible green algae that is widely distributed along the coasts of the world's oceans. The type species within the genus Ulva is Ulva lactuca, lactuca being Latin for "lettuce". The genus also includes the species previously classified under the genus Enteromorpha, the former members of which are known under the common name green nori. Individual blades of Ulva can grow to be more than 400mm (16") in size, but this only occurs when the plants are growing in sheltered areas. There are some indications that this genus is of tropical in origin. In the tropics, the diversity of Ulva is much higher than that in temperate or sub-polar regions.
Sea lettuce is eaten by a number of different sea animals, including manatees and the sea slugs known as sea hares. Many species of sea lettuce are a food source for humans in Scandinavia, Great Britain, Ireland, China, and Japan (where this food is known as aosa). Sea lettuce as a food for humans is eaten raw in salads and cooked in soups. It is high in protein, soluble dietary fiber, and a variety of vitamins and minerals, especially iron.
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Sargassum is a genus of brown (class Phaeophyceae) macroalgae (seaweed) in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral reefs, and the genus is widely known for its planktonic (free-floating) species. While most species within the class Phaeophyceae are predominantly cold water organisms that benefit from nutrients upwelling, genus Sargassum appears to be an exception to this general rule. Any number of the normally benthic species may take on a planktonic, often pelagic existence after being removed from reefs during rough weather; however, two species (S. natans and S. fluitans) have become holopelagic—reproducing vegetatively and never attaching to the seafloor during their lifecycle. The Atlantic Ocean's Sargasso Sea was named after the algae, as it hosts a large amount of sargassum.
Sargassum was named by the Portuguese sailors who found it in the Sargasso Sea after a species of rock rose (Helianthemum) that grew in their water wells at home and that was called sargaço in Portuguese (Portuguese pronunciation: [sɐɾˈɣasu]).
The Florida Keys and its smaller islands are well known for their high levels of Sargassum covering their shores. Gulfweed was observed by Columbus. Although it was formerly thought to cover the entirety of the Sargasso Sea, making navigation impossible, it has since been found to occur only in drifts.
Sargassum is also cultivated and cleaned for use as an herbal remedy. Many Chinese herbalists prescribe powdered Sargassum in paper packets of 0.5 gram, to be dissolved in warm water and drunk as a tea. When sold in this application it is commonly referred to as Seaweed Sargassum Tea.
A description of the experience
J Nutr. 2007 Dec;137(12):2691-5.
High iron content and bioavailability in humans from four species of marine algae.
García-Casal MN1, Pereira AC, Leets I, Ramírez J, Quiroga MF.
Searching for economical, nonconventional sources of iron is important in underdeveloped countries to combat iron deficiency and anemia.
Our objective was to study iron, vitamin C, and phytic acid composition and also iron bioavailability from 4 species of marine algae included in a rice-based meal. Marine algae:
- Ulva sp - sea lettuce
- Sargassum sp,
- Porphyra sp, and
- Gracilariopsis sp
were analyzed for monthly variations in iron and for ascorbic acid and phytic acid concentrations.
A total of 96 subjects received rice-based meals containing the 4 species of marine algae in different proportions, raw or cooked. All meals contained radioactive iron. Absorption was evaluated by calculating the radioactive iron incorporation in subjects' blood.
Iron concentrations in algae were high and varied widely, depending on the species and time of year. The highest iron concentrations were found in Sargassum (157 mg/100 g) and Gracilariopsis (196 mg/100 g).
Phytates were not detected in the algae and ascorbic acid concentration fluctuated between 38 microg/g dry weight (Ulva) and 362 microg/g dry weight (Sargassum).
Algae significantly increased iron absorption in rice-based meals. Cooking did not affect iron absorption compared with raw algae.
Results indicate that Ulva sp, Sargassum sp, Porphyra sp, and Gracilariopsis sp are good sources of ascorbic acid and bioavailable iron. The percentage of iron absorption was similar among all algae tested, although Sargassum sp resulted in the highest iron intake. Based on these results, and on the high reproduction rates of algae during certain seasons, promoting algae consumption in some countries could help to improve iron nutrition.
PMID: 1802948