Nutraceuticals, trace metals and radioactivity in edible seaweeds for food safety: An overview

Seaweeds are of potential nutraceutical and medicinal values due to their wide range of constituents such as proteins, carbohydrates, fatty acids, peptides, minerals, vitamins, and hydrocolloids. However, the seaweeds accumulate toxic heavy metals from the habitats, depending on land discharges, seasons, growth phase and duration of life cycle. As seaweeds are widely used as seafood and food ingredients of various delicious food items, some countries have regulatory rules for daily consumption of seaweeds and seaweeds based food items due to presence of heavy metals, but many countries even don’t have such kind of regulatory limits, according to Food Administration organization (FAO) and World Health Organisation (WHO). Realising the importance of this issues, the present review aims to revaluate the biochemical composition of edible seaweeds including their heavy metals and radioactive elements for their potential use for human consumption so as to ensure food safety of the seaweeds.

Seaweeds are marine macro algae, economically important marine renewable resources, which are utilized as food ingredients and food items, fodder for animals, soil manure, salts, iodine, and phyco-colloids like agar, alginate, carrageenan and furcellaran in different countries of the World. The marine macroalgae contain proteins and carbohydrates higher 1983). Seaweeds have excellent nutritional composition of proteins, carbohydrates, lipids, minerals, vitamins and all essential amino acids, fatty acids than the common edible vegetable (Vijayaraghavan et al. 1980 andParekh et al. 1982). The nutraceutical composition of seaweeds varies with species, geographical area of distribution, seawater temperature, salinity, light, nutrients and the terrestrial influences (Jensen, 1993;Dawes et al. 1993; Kaehler et al. After evaluation of chemical composition and nutraceutical value, some marine macro algae are cultivated and intensively used as nutritious food (Darcy-Vrillon, 1993 and Mabeau Worldwide, only about 221 species of seaweeds are commercially exploited, including 125 Rhodophyta, 64 Phaeophyta and 32 Chlorophyta. Of these 66 of 145 species including 79 Rhodophyta, 38 Phaeophyta and 28 Chlorophyta are directly used as food for human consumption. For industrial purpose, 101 species are used in phycocolloids industries, 41species as alginophyte i.e. alginic acid producing algae, 33 agar producing algae called agarophyte (agar producing seaweeds) and 27 carrageenophytes (carrageenan producing seaweeds). Totally 24 species are used in traditional medicines, 25 species for agriculture, animal feeds and fertilizers, and 12 species are cultivated in 'marine agronomy'  and Zemke-W Hawaiian Islands, 70 seaweeds are edible, among which 40 seaweeds are consumed as regular diets on par with nutritious non-vegetarian food items composed with fish and meat (Karla Daily intake of seaweed in Japan is up t 8.5 g/d in Korea, according to third Korean National Health and Nutritional Survey (Teas et al., 2004). In Korea, seaweed diet is mainly based on Undaria pinnatifida, and Apr 2018 Page: 947 6470 | www.ijtsrd.com | Volume -2 | Issue -3

Scientific (IJTSRD)
International Open Access Journal Nutraceuticals, trace metals and radioactivity in edible seaweeds for food safety: An overview Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Nadu, India sential amino acids, fatty acids than the common edible vegetable (Vijayaraghavan et al. 1980 and1982). The nutraceutical composition of seaweeds varies with species, geographical area of distribution, seawater temperature, salinity, light, nutrients and the terrestrial influences (Jensen, 1993;et al. 1996; Dawes, 1998). After evaluation of chemical composition and nutraceutical value, some marine macro algae are cultivated and intensively used as nutritious food Vrillon, 1993 andMabeau et al. 1993). Worldwide, only about 221 species of seaweeds are commercially exploited, including 125 Rhodophyta, 64 Phaeophyta and 32 Chlorophyta. Of these 66 of 145 species including 79 Rhodophyta, 38 Phaeophyta rophyta are directly used as food for human consumption. For industrial purpose, 101 species are used in phycocolloids industries, 41species as alginophyte i.e. alginic acid producing algae, 33 agar producing algae called agarophyte s) and 27 carrageenophytes (carrageenan producing seaweeds). Totally 24 species are used in traditional medicines, 25 species for agriculture, animal feeds and fertilizers, and 12 species are cultivated in 'marine agronomy' (Pereira constitute over 95% of seaweed consumption. In Japan and China, Monostroma sp., Hizikia fusiformis, Ulva sp., and Palmaria palmata are used as the most commonly consumed seaweeds as in Western dietetic habits (FAO, 2003). Other seaweeds used for human consumption are Gracilaria, Gelidium, Sargassum, Caulerpa and Ascophyllum. Using this information, a comparison is made using common measures (portions) of usual foods in an occidental diet. Worldwide production of marine macro algae: Top five cultivated seaweeds in the world are Laminaria sp., Porphyra sp., Undaria sp., Eucheuma sp., and Gracilaria sp., which together accounts for 5.97 million metric tonnes (Academy of agricultural sciences, 2003). China is the highest in seaweed production (59% and 4.093 fresh wt. Million tonnes), followed by other countries -Korea, Japan, Philippines, Norway, Chile and France (90% and 6.263 fresh wt. Million tonnes). The seaweeds resources along the Indian coast can be at around 100,000 tonnes including explored area -with 73,044 tonnes and unexplored area-with -27,000 tonnes. State wise annual yield of seaweeds in tonnes (fresh wt.) is in decreasing order: Tamilnadu  Mastocarpus stellatus 4.

Rhodophyta:
The commonly used red seaweeds for human consumption are Catenella repens Aglaothamnion uruguayense, Cryptonemia seminervis, Porphyra columbina, Porphyra sp., Halymenia sp., and Chondrus crispus. According to Lourenço et al. 2002, while analysing the amino acid composition and protein content of 19 tropical seaweeds, it showed that the content of aspartic and glutamic acid of green algae are lower than red and brown algae; amino acid residues vary from 23.1% in Aglaothamnion uruguayense, and nitrogen-protein conversion factor ranges from 3.75 for Cryptonemia seminervis. The lipid content of Sea Spaghetti is higher (p<0.05) than that of Nori, but similar (p>0.05) to Wakame. Sea Spaghetti and Wakame have higher (p<0.05) ash content 30% and 37% respectively than Nori (Cofrades et al. 2010). Kappaphycus alvarezii contains carrageenan such as 3,6-anhydro-Dgalactose, Calliplepharis jubata and non-fructified thalli of Eucheuma denticulata have iota-carrageenan consequently Kappa/iota-hybrid carrageenan of  (Rupérez 2002). Chondrus crispus and Porphyra tenera contain high amount of soluble and insoluble fibres as well sulphate (2.8-10.5%), lipids (0.2-2.5%), ashes (21-39.8%) and extractable polyphenols -0.4% in the red seaweeds and these red seaweeds contain higher protein (20.9-29.8%) than brown seaweed (6.9-16%), (Rupérez, 2001). About Trace metals of edible seaweeds: Hiziki is the most edible species in the foreign country. According to National Metrology Institute of Japan, the values in Hijiki and Ulva lactuca fell within the range of certified value ( Table 2). The red algae (Porphyra tenera and Porphyra species) contain 17-28 µg/g of arsenic (dry wet) almost in the form of arsenosugar (Shibata et al. 1990& Francescom et al. 1993). To test the quality assurance of seaweeds based food items for heavy metals content, the limits of detection (LOD) and limits of quantification (LOQ) were calculated for Hiziki and compared with certified values. It reveals that Hiziki content heavy metals below toxic level (Khan et al. 2015). In open ocean water arsenic typical levels are 1-2 g As /L (Francesconi and Edmonds, 1998;WHO, 2001). Arsenic level is most constant in deep ocean waters, while levels in surface waters show seasonal variation. Arsenic (As) are found in seafood in different forms such as Arsenate (As [V]), Methyl Arsonate (MA), Arsenobetaine, Trimethyl Arsine, Oxide (TMAO), Arsenite (As [III]), Dimethyl Arsinate (DMA), Arsenocholine, Tetramethyl Arsonium Ion (TETRA). So, for safety assurance the edible seaweeds arsenic content is analysed in details ). According to UK Total Diet Study, 1997, the concentration of 4.4 mg/kg of total arsenic in the fish group has been accounts 94% of the average population exposure to arsenic but seaweed was not included in these total diet samples (Ysart et al., 2000). In 1989, according to JECFA, the provisional tolerable weekly intake (PTWI) of arsenic is of 15 µg/kg body weight. Some of seaweeds had been analysed for its heavy metals compositions, of which some seaweeds heavy metals composition had been tabulated in table 3. It is clearly indicated in the table 4 of certified values of heavy metals that the edible seaweeds contain lower heavy metals than certified value of heavy metals, so it can be concluded that these studied seaweeds will be safe for use and consider it, as food items in future. The heavy metals arsenic is a toxic metal and focused of study to analyse its presence in food items, so likewise seaweeds are also considered as food items, so the arsenic composition of seaweeds were tabulated in the table 5 to identify the seaweeds as safe food items with respect to its arsenic content also.

Radioactivity of seaweeds:
Kelp is a strong bio-concentrator of radioisotopes in water. It is concluded that Post-Fukushima, there was a statistically significant rise in the radioactivity of nori seaweed than compared to Pre-Fukushima seaweed sampled (p<0.05). In addition, radioactivity in water threatens in water to destroy Canada's marine aquaculture and seafood industries. The Fukushima 1 Nuclear Power Plant accident in March 2011 released an enormously high level of radionuclides into the environment, a total estimation of Bq. represented by mainly radioactive Cs, Sr and I. Because these radionuclides are biophilic, an urgent risk has arisen due to biological intake and subsequent food web contamination in the ecosystem, showed the highest ability to eliminate radioactive Cs from the medium by cellular accumulation. The issues of radioactivity pollution, is now an international concern to stop the inclusion of radioactivity to the marine environment (WHO, 2016  .) and tested for presence of radioactivity and it has been revealed that as seaweeds accumulate 137 Cs in tissues, so bio-monitoring of 137 Cs using seaweeds may be used to track the metals loads in different geographical region and as seaweeds grow and turn over rather rapidly, so they have been not influenced by bio-concentration through food chain (Kawai et al. 2014).
After TEPCO nuclear power plant leak, radioactive iodine has been detected in six seaweeds samples in South Korea. However, 14 seaweed species are free from radioactivity except very small amount of radioactivity in tangle weed (Laminaria japonica). So, if the marine environment is contaminated by radioactive substances, then there is a possibility of accumulation of radioactive substances in seaweeds, still it is in negligible amount. It has been reported that after the consumption of Kelp, the uptake and deposition of radioactive Iodine are reduced in very low concentration (Irie et al. 2012).
The meltdowns at nuclear power plants (such as Chernobyl or Three Mile Island) releases large amounts of I 131 and other radioactive elements into the ocean and atmosphere. According to the National Institute of Health, from the nuclear accident at Chernobyl the radioactive I 131 release in high amount to the environment developing thyroid cancer worldwide. The mixing of such kind of radioactive isotope in the oceans increases the risk of circulation of radioactivity throughout the World. The seaweeds especially brown seaweeds Laminaria sp., Sargassum sp., Turbinaria sp. and Ascophyllum sp. have larger surface area and accumulate high Iodine, so, such kind of sudden accidental release of radioactivity in to the ocean may increase the risk of accumulation of radioactive Iodine (Drum, 2012). In March, 2011 the meltdown of three nuclear reactors including other two disaster a major earthquake and a resultant International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470 @ IJTSRD | Available Online @ www.ijtsrd.com | Volume -2 | Issue -3 | Mar-Apr 2018 Page: 955 tsunami releases huge radioactivity to the air. To cool down the high heat of nuclear power plant, huge water is flooded to that place and that washed water flows to the ocean producing radioactivity to the ocean; the reports for three years 2013, 2014, 2016, explain that releases of radioactivity are still continuous from that area which gradually are increasing of radioactivity in ocean area.
In spite of the issue of radioactivity, it is believed that the seaweeds grow rather rapidly and, hence, turnover rapidly, so that they exert no influence of bioconcentration of radioactive substance (Cs 137 ) through the food chain (Kawai et al., 2014). Moreover, the microalgae and aquatic plants notably eustigmatophycean unicellular algal strain, nak9 can eliminate radioactive cesium, iodine and strontium, as proved in experimental studies (Shin-ya Fukuda et al., 2013). This will be an important strategy for decreasing radio pollution.

Discussion:
Traditionally, seaweeds are a natural source of food and medicines in Asian countries, especially Japan, Korea, China, Vietnam, Indonesia and Taiwan. Worldwide, six million tons of fresh algae are now cultivated and an amount of around 90% is for the commercial demand (FAO, 2002). Globally, a total of 147 seaweeds are edible for their nutritional composition (Leonel et al. 2015). Seaweeds contain an array of valuable minerals and the commercially available edible seaweeds contain less quantity of toxic heavy metals, so consumption of seaweeds within the range limit mentioned by WHO/FAO will not deliver any harmful effect (Almela et al. 2002;. The edible seaweeds are safe for human consumption when the concentration of the above elements mentioned in edible seaweeds compared to World Health Organisation of the United Nations (WHO/FAO).
According to mentioned certified values and the normal toxic metals content of seaweeds, it is concluded that seaweed's content the toxic metals below its threshold levels, so seaweeds as food and food ingredient, will be safe and there is no chance to be bio-concentrated and biomagnified as well as toxicity after consumption of it.
In order, to find out the exact circulation of radioactivity through the different trophic levels of ocean ecosystem, requires an extensive estimation of radioactivity in different plants and animals in marine environment. This will help to understand whether the radioactivity is magnified in any particular organisms, or equally distributed to all animals and plants, and accumulated in sediments and water. Species specific stepwise estimation of radioactivity is required in future to predict the future risk of radioactivity.
Some heavy metals content of some mostly used edible seaweeds showed that estimated values are lower than the certified values of uptake. So, it is declared to be safe as edible items. Some of the literatures also show that after cooking, the metals are releasing into water and the content of heavy metals in cooked seaweeds are lower than the raw seaweeds. So, before making any food items with seaweeds, if seaweeds are slightly boiled with water and that water will be removed completely from seaweeds; after that if seaweeds are used for preparing food items. It will be safer. In spite of superior nutritional properties, high concentration of certain nutrients may be problematic for some, for example, overconsumption of vitamin K can interfere with blood thinning medications. Certain seaweeds have high potassium contents, which might cause issues for those with kidney problems. While the iodine content makes it especially beneficial for thyroid health, consuming too much iodine can have the opposite effect.

Future Directions:
In this review, the overall description of the biochemical composition of marine macro algae, its use as food items for human being are analysed to identify the properties of marine macro algae for use as food item in daily diet. We take daily food such as carbohydrate, protein, fat, minerals, micronutrients and macronutrients as required amount through rice, vegetables, oil, milk, fish, meat and other food ingredients; but the seaweeds contain all the mentioned food ingredients in them, so if we find out a single macro alga which is composed of all require quantity of dietary amount of daily food, we can used it as a food supplement. This review is purposive to create a nutritional detail of marine macro algae to popularize their utilization and consumption throughout the world. Comparative details with several commonly used seaweeds with daily used vegetable are available to find out the seaweeds vegetable as a potential alternative for daily diet. The nutrient composition of seaweeds varies on the basis of water quality and climatic conditions as well as nutrients supply through the seawater. This indicates