Phytoplankton, seaweeds and symbiotic dinoflagellates (unicellular, biflagellate organisms) in corals and sea anemones are marine algae. Marine algae are the oldest members of the plant kingdom, extending back 3 billion years. Algae encompass a diverse group of autotrophic organisms, ranging from unicellular to multicellular forms. Some of the larger and more complex algae, such as giant kelp, are more commonly referred to as seaweeds. Seaweeds are classified as Green algae (Chlorophyta), Brown algae (Phaeophyta), Red algae (Rhodophyta) and some filamentous Blue-green algae (Cyanobacteria).
Algae have a long traditional history of use in Asian countries, playing a role as a main staple food in the diet (dos Santos Pires-Cavalcante, 2011). In western cultures, the consumption and production of algae have increased and many countries, such as Canada and the United States, have begun cultivating different types of algae for various products, including natural health products, fertilizers, soil conditioners, livestock feed, chemical products (hydrocolloids or gelling agents) and cosmetics (dos Santos Pires-Cavalcante, 2011 and McHugh, 2003). Over the past few years algae have also become increasingly popular as a “health food”; in particular nori, wakame and dulse are sold as packaged foods in supermarkets. Algae has been shown to be low in fat, high in fiber and contain calcium, magnesium, phosphorus, potassium, iron, iodine, and water- and fat-soluble vitamins (carotenoids, vitamins B, C and E) (Dhargalkar and Verlecar 2009; Taboada and others 2010). Vitamins and minerals are highly variable in algae and depend on factors such as seasonality, environmental conditions of temperature, salinity, luminosity, freshness, and the method of preservation and processing (dos Santos Pires-Cavalcante, 2011).
A recent study was published in the Journal of Food Science evaluating seasonal changes of α-tocopherol in Green Marine Algae (Caulerpa genus) (dos Santos Pires-Cavalcante, 2011). A total of 5 species of green marine algae of the Caulerpaceae family (Caulerpa cupressoides, C. sertularioides, C. racemosa, C. mexicana, and C. Prolifera) were collected each month from January to December 2006, at Pacheco Beach, in the state of Ceara, Brazil to assess the effect of the drying process on α-tocopherol levels. The results for fresh algae indicate that daily portions from the Caulerpa species, sufficient to be deemed an excellent source (11 -175 g) or a useful source (4-58 g) of vitamin E, would be relatively small. Similarly, daily portions of dry Caulerpa sufficient to supply ½ RDA (excellent source) or 1/6 RDA (useful source) of vitamin E ranged from 13-70 g and 4-24 g respectively. The study also looked at the annual distribution of α-tocopherol among the species and no pattern was observed. Furthermore, the drying process resulted in losses of up to 90% α-tocopherol (dos Santos Pires-Cavalcante, 2011).
The safety of algae has been receiving considerable attention over the past few years as it is know that certain cyanobacteria and phytoplankton can produce toxic by-products, under specific environmental conditions, which accumulate in the food chain (Rossini, 2010). These commonly concentrate in filter feeding bivalves, burrowing and grazing organisms, herbivorous and predatory fish. In particular the Natural Health Product Directorate (NHPD) under the “Annex to the Natural Health Products (NHPs) Compliance and Enforcement Policy for Exempt NHPs under the Natural Health Products (Unprocessed Product Licence Applications) Regulations (UPLAR)” will not be issuing exemptions to products containing blue green algae (Aphanixomenon flos-aquae), as these have a high probability of being contaminated with the hepatotoxins microcrystin-LR and -LA (http://www.hc-sc.gc.ca/dhp-mps/compli-conform/info-prod/prodnatur/annex-complian-conform-pol-eng.php). It is important to note that other algae, in particular phytoplankton, can also produce toxic by-products (domoic acid and saxitoxins), resulting in paralytic shellfish poisoning (PSP). This only occurs during a harmful algae bloom and these are naturally occurring events which are monitored by country specific regulatory bodies prior to harvesting of fish and molluscs in the area. Safety guideline levels for different algal toxins have been established by regulatory bodies worldwide (http://www.issha.org/Welcome-to-ISSHA/Harmful-Algae-Links/Phycotoxins/Saxitoxins-PSP) in fish and molluscs. These guidelines are based on acute effects established from laboratory experiments and reported adverse reaction reports. Although there are an estimated 3,400 to 4,000 known species of phytoplankton, only 60-80, less than 2%, of the species are considered harmful (Smayda, 1990).
Since there is a consumer health trend for products containing various algae species, further studies are required to advance an understanding of the long term low level exposure of algal toxins. Moreover, since algae have many health benefits, a concerted effort between algae suppliers and manufacturers and the NHPD is required to help establish good agricultural practices for the harvesting, cultivation, and collection of algae and good manufacturing practices for algae-containing natural health products.
References:
Dhargalkar VK, Verlecar XN. 2009. Southern ocean seaweeds: a resource for exploration in food and drugs. Aquaculture 287:229–42.
McHugh, Dennis J. 2003. “9, Other Uses of Seaweeds”. A Guide to the Seaweed Industry: FAO Fisheries Technical Paper 441. Rome: Fisheries and Aquaculture Department, Food and Agriculture Organization (FAO) of the United Nations.
Pires-Cavalcante KMS, de Alencar DB, de Sousa MB, Sampaio AH, Saker-Sampaio S. 2011. Seasonal Changes of α-Tocopherol in Green Marine Algae (Caulerpa genus). Journal of Food Science. Epub.
Rossini GP, Hess P. Phycotoxins: chemistry, mechanisms of action and shellfish
poisoning. EXS. 2010;100:65-122.
Smayda Tj. 1990. Novel and nuisance phytoplankton blooms in the sea. Evidence for a global epidemic. In: Graneli E, Sundstrom B, Edler L, Anderson DM, (ed) Toxic Marine phytoplankton. Elsevier. New York, p 29-40.
Taboada C, Mill´an R, M´ıguez I. 2010. Composition, nutritional aspects and effect on serum parameters of marine algae Ulva rigida. J Sci Food Agric 90:445–9.
Van Dolah FM, Roelke D, Greene RM. 2001. Health and ecological impacts on harmful algal blooms: risk assessment needs. Human and Ecological Risk Assessment 7:1329-1345.