How Much Iodine is in Shrimp?

1Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UKFind articles by

2Institute for Food Research and Nutrition, University of Reading, Agriculture Building, P. O. Box 2376, Earley Gate, Reading RG6 6AR, UK; moc. liamg@306uahcct (T. C. C. ); ku. ca. gnidaer@snevig. i. d (D. I. G. )Find articles by.

2Institute for Food Research and Nutrition, University of Reading, Agriculture Building, P. O. Box 2376, Earley Gate, Reading RG6 6AR, UK; moc. liamg@306uahcct (T. C. C. ); ku. ca. gnidaer@snevig. i. d (D. I. G. )Find articles by.

Iodine is an important nutrient for human health and development, with seafood widely acknowledged as a rich source. Because of the growing world population, there is now a wider range of wild and farmed seafood to choose from. But as aquaculture production has gone up, feed ingredients have changed in ways that affect the nutritional value of the final product. This study looked at how much iodine is in wild and farmed seafood that people in the UK can buy and how much of their current iodine intake comes from food. Ninety-five types of seafood from UK stores were bought and analyzed. These included marine and freshwater fish and shellfish from both wild and farmed sources. Iodine contents ranged from 427. 4 ± 316. 1 to 3. 0 ± 1. A haddock (Melanogrammus aeglefinus) and a common carp (Cyprinus carpio), both in the order shellfish, had a flesh wet weight of 6 µg·100 g−1. Overall, iodine levels were higher in wild fish than in farmed fish, except for aquaculture species that were not fed (bivalves). However, there were no important differences found between Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), and turbot (Psetta maxima) that were wild or farmed. European seabass (Dicentrarchus labrax) and seabream (Sparus aurata) from farms had lower iodine levels than their wild counterparts, while Atlantic halibut (Hippoglossus hippoglossus) had higher levels. This is likely because of the type and amount of feed ingredients used. By following the UK’s food guidelines for fish, eating some Atlantic mackerel (Scomber scombrus), or haddock, which is high in oil, would give you two-thirds of the weekly recommended iodine intake (980 µg). In contrast, actual iodine intake from seafood consumption is estimated at only 9. 4–18. 15% of the UK’s recommended daily amount of nutrients (140% of the recommended amount for men and 140% of the recommended amount for women) across all age groups and genders, with women getting less than their male counterparts.

Iodine is an important trace element that is needed to make the thyroid hormones thyroxine and tri-iodothyronine [1,2,3]. It also plays a big part in controlling the growth and metabolism of vertebrates. If people don’t get enough iodine, it can lead to a number of known health problems, including goitre in the thyroid and problems with brain development and function that can happen at any age, from pregnancy to old age [1,4,5]. As a result, health groups around the world have set reference nutrient intake (RNI) levels to make sure that everyone gets enough of the nutrients they need to stay healthy. The current RNI for adults in the UK is 140 µg·day−1 [6]. This is a little less than the 150 µg·day−1 RNI for adults and ≥200 µg·day−1 RNI for pregnant and breastfeeding women that the World Health Organization (WHO) and other health authorities recommend [7,8,9,10]. These allowances are mostly expected to be satisfied through dietary consumption. Even though nutrition has gotten better in the UK and Western Europe as a whole, there is some worry that iodine intake has become mild to moderately inadequate, especially among more vulnerable groups like young children and women of childbearing age [4,5,11,12,13,14].

In most Western countries, like the UK [15,16,17,18,19], milk and dairy products are the main foods that people eat that contain iodine. However, the amount of iodine in these foods depends on a lot of things, like the drinking water and the fortification of animal feed [20,21,22,23]. Iodine (as iodide), on the other hand, is naturally found in high concentrations in aquatic organisms, especially marine ones [24,25]. Because of this, seafood is often thought to be the best way for people to get iodine and other nutrients that are good for their health and development. In fact, many government and health groups say that eating at least two servings of fish a week is an important part of a healthy, well-balanced diet [26,27,28,29]. Thus, routine seafood consumption has the potential to facilitate populations achieving a sufficient iodine intake.

Recently, the amount of seafood grown in farms (aquaculture) has increased so much that it now provides more seafood for human consumption than fish caught in the wild [30]. This growth is mostly due to the world’s population continuing to rise. This has led to a higher demand for both traditionally farmed species like carps and tilapias and high-value farmed species like Atlantic salmon (Salmo salar), European seabass (Dicentrarchus labrax), and marine shrimp [31]. But getting the right feed ingredients for the aquaculture industry, which is growing very quickly, has been one of the biggest problems with its success. Because of this, feed formulas have changed, especially for marine carnivorous species. Instead of using fish meal and fish oil, which are limited and hard to find in the ocean, they now use alternatives like plant-based raw materials from land that are generally thought to be more sustainable [32]. Since then, there have been lower levels of some good nutrients found in both fish feed and flesh [33,34,35]. This makes people wonder if farmed fish can provide enough of these nutrients for people to eat without changing the current rules about eating fish [36].

Although the iodine contents of seafood have been studied (e. g. , [15,37,38,39,40,41,42]), they are generally limited to only a few species most commonly consumed. Food composition tables, like McCance and Widdowson’s The Composition of Foods, give us useful information about nutrients that help us figure out how healthy and well-nourished a population is [43]. But they need to be kept up to date so the information is still useful [44]. The UK’s dataset on popular fish and fish products was last updated in 2013 [45]. In the time since then, consumers have had access to a wider range of fish, and the nutrients in farmed species have changed. So, the goal of this study was to look at and compare the iodine levels in 95 seafood products that are sold in the UK. These products included marine and freshwater fish, shellfish (crustaceans, bivalves, and cephalopods), and fish that came from both farms and the wild. The data was then used to estimate how much iodine people are eating now.

3. Wild Versus Farmed Seafood

In recent years, aquaculture has provided more seafood for human consumption than wild capture fisheries [30]. Still, farmed seafood has been criticized many times, and it is often thought to be less healthy than seafood that comes from the wild. Of the 95 seafood samples analysed in the current study, 21 were of farmed origin. Of these, eight were identified as having a same-species, or equivalent, wild counterpart. There were wild and farmed Atlantic salmon, as well as keta (Oncorhynchus keta), pink (O. rostralis), and other wild Pacific salmon types. gorbuscha) and sockeye. Based on the measured iodine contents, no difference was found between wild and farmed Atlantic salmon, 17. 0 ± 4. 0 and 13. 2 ± 6. 8 µg·100 g−1 flesh ww, respectively ( a). An important difference was found between Atlantic and Pacific salmon species: sockeye had a lot more iodine than other species (24). 9 ± 13. 3 µg·100 g−1) than both farmed Atlantic salmon and the other wild Pacific salmon, keta and pink (12. 3 ± 2. 1 and 10. 4 ± 3. 7 µg·100 g−1, respectively). Conversely, the mean iodine content for sockeye salmon (13. 3 µg·100 g−1) was observed to be in the range of all other salmon (9. 9–17. 0 µg·100 g−1). As we’ve already talked about, the iodine content of the same species of wild fish can change depending on the season and where it lives [38,40]. For the other farmed salmonid, rainbow trout (O. mykiss), no significant differences were observed between marine and freshwater reared trout (10. 7 ± 5. 5 and 11. 6 ± 9. 2 µg·100 g−1), with neither showing differences with wild sea trout (S. trutta, 17. 3 ± 3. 4 µg·100 g−1) ( b). There was no difference in the amount of iodine in freshwater and marine-raised trout, which are usually harvested at 400 g and 3 kg, respectively. This may come as a surprise, since marine waters and the organisms that live in them are usually thought to be better sources of iodine [39,57]. Fish that are raised in farms, on the other hand, are usually fed food that is made to at least meet the nutritional needs of the species being raised [61]. So, adding extra iodine to farm-raised fish might not make any of the differences that were thought to exist between fish raised in fresh water and fish raised in the ocean, especially if the amount of iodine in the food is much higher than what is found in the environment. In the same way, any differences in the nutrients found in different animals of the same species that are raised on farms are probably due to different feed formulations caused by different farming methods [63].

All of the farmed salmonids, i. e. Atlantic salmon and rainbow trout, whether they were raised in salt water or fresh water, had similar amounts of iodine in their flesh, which suggests that they ate foods with similar amounts of iodine. Correspondingly, both farmed seabass and seabream also contained a similar iodine level, ~12. 0 µg·100 g−1, to the farmed salmonids ( ). However, this was significantly lower than that found in wild seabass ( c) and seabream ( d), 36. 1 ± 16. 0 and 53. 9 ± 23. 2 µg·100 g−1, respectively. The problem of finding the right food for the fish has become a big problem as aquaculture production has grown to feed a growing population. Farm-raised fish feeds, especially for marine carnivorous fish, have changed from a diet high in fish meal and fish oil, which are limited marine ingredients, to a diet high in plant-based ingredients [32]. So, as the use of plant-based ingredients has grown, the amounts of some good nutrients that come from marine ingredients have gone down in fish feed and flesh. These nutrients include long-chain omega-3 fatty acids, selenium, and iodine [33,34,35]. And just like with selenium, the amount of iodine in plant foods depends on how much iodine is in the soils where the plants are grown [64,65]. Additionally, cruciferous plants like rapeseed, which is commonly used in aquafeeds [32,35], contain glucosinolates that are known to cause goitrogenic effects by limiting the availability of iodine and causing changes in the shape and function of the thyroid, as well as decreasing the plant’s ability to taste good and improve overall growth and production [2,61]. So, since iodine is important for fish growth [2,3], it might be necessary to add more iodine to feeds that are mostly made of plants.

The iodine requirement of farmed fish is estimated to vary between 0. 6 and 5. 0 mg. kg−1 diet, based on rearing conditions, species and life-stage [2,3,61,66]. Freshwater fish for example are more dependent upon dietary sources of iodine. Similarly, fish raised in closed-water systems (i. e. , recirculation) and systems that use ozonized water are more likely to show signs of goitre. Fish that eat meat are more likely to be affected than fish that eat plants or both [66,67]. The low levels of iodine in farmed freshwater carp, tilapia, and striped catfish (Pangasius hypophthalamus, also known as Basa or river cobbler) of 2

% are likely due to this. 97 ± 1. 58, 4. 71 ± 1. 90 and 6. 16 ± 3. 46 µg·100 g−1 flesh ww, respectively ( ). But adding iodine to fish food or foods that are high in iodine, like seaweed, has been shown to raise fillet levels, improve growth, lower stress, and protect against disease without changing the thyroid status [2,68,69]. Even so, the amount of iodine in aquafeeds right now is probably enough to meet the fish’s basic needs, but it has decreased the amount that humans can get from eating fish.

The farmed Atlantic halibut had a much higher iodine content than the wild fish of the same species, 33. 4 ± 10. 9 and 20. 4 ± 8. 6 µg·100 g−1, respectively ( e). This is in contrast to Nerhus et al. [40] found that wild Atlantic halibut caught in the Barents and Norwegian Seas had similar average iodine levels to this study (18 and 23 µg·100 g−1, respectively). However, farmed Atlantic halibut had a lower level, only 11 µg·100 g−1. There were big differences in the amounts of iodine found in farmed halibut between studies. This might be because the aquafeeds used in each study had different ingredients. It is important to make sure that the types of ingredients and amounts that are used in fish food meet their nutritional needs [61]. Even though fish meals usually have a lot more iodine than plant and animal proteins, the amount of iodine can vary a lot depending on where the fish comes from. For instance, herring and capelin meals were reported to contain 5–10 mg. kg−1, while Atlantic white fish meals can contain upwards of 60–90 mg. kg−1 [66]. Additionally, the iodine content of farmed halibut was almost identical to that measured in farmed turbot (32. 4 ± 6. 4 µg·100 g−1), which in turn was lower, but not significantly, than the content of wild turbot (52. 0 ± 39. 9 µg·100 g−1) ( f). This could mean that the diets for farmed halibut and turbot were made with similar amounts and types of marine ingredients compared to the feeds for farmed salmon, trout, seabream, and seabass, which all had similar amounts of iodine. European countries, like Norway and the UK, raise a lot less farmed halibut (1918 metric tons) and turbot (10,116 MT) than they do farmed salmon (1,552,335 MT), trout (242,000 MT), seabream (92,000 MT), and seabass (84,400 MT) [70,71]. So, both the farmed halibut and turbot sectors can use more of the limited marine ingredients, both in terms of price and volume, than the species that produces a lot more. This could also explain why Arctic char (Salvelinus alpinus), the other farmed salmonid that was raised in fresh water and should have had low iodine levels, had a higher content (18). 7 ± 6. 3 µg·100 g−1) than farmed salmon, trout, seabass, and seabream. The UK produces about 7 MT of char each year, while 166,000 MT of farmed salmon is raised there [70,72].

It should be noted that certain stocks of wild fish are considered as being critical. To be exact, many of the wild fish species that were looked at in this study, like wild Atlantic salmon and halibut, are not often, if ever, found in the main fish stores in the UK (i.e. e. supermarkets) and are getting harder and harder to find at specialty stores and fishmongers. This is on top of the normal difficulties that come with buying wild fish because of the seasons. Farmed fish therefore represent an increasingly important food source in delivering essential nutrients to the human consumer.

Materials and Methods

Between January 2016 and December 2019, 95 different types of fresh and frozen fish, shellfish (crustaceans and mollusks), and fish from farms and the wild were bought from a range of UK stores (supermarkets, fishmongers, and online stores) (See for details). At least three samples of the same species were taken at different times and from different stores, when possible, to lower the chance that they came from the same fish or catch. When the samples got to the lab, they were thawed if needed and then skinned, boned, or shelled. The main edible flesh was then mixed into a smooth pâté using a blender mixer (Blixer® V). V. , Robot-Coupe, Vincennes, France). All samples were raw unless otherwise stated. Large whole fish or cuts of large fish were usually judged on their own, but smaller fish like European anchovies (Engraulis encrasicolus) and sprats (Sprattus sprattus) and shellfish bought at the same time were judged as a whole. Five to ten grams of the homogenate were taken out and dried in an oven at 110 °C for twenty hours [46]. The rest of the sample was kept at -20 °C for further study. The sample that had been dried was weighed again and then ground into a fine powder. The amount of water in the powder was written down so that the results could be given as a wet weight (ww). Iodine tests were done on the dried samples that were kept in a desiccator in the dark and under vacuum until they were sent to the University of Reading. Sample identities (i. e. , species, wild/farmed location, etc. ) were based on the product/label information available at the time of purchase. According to the Animal Welfare and Ethical Review Body (AWERB) at the University of Stirling, this study was okay from an ethical point of view (AWERB/167/208/New Non ASPA).

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Tip of the day: more iodine in the head of a shrimp than in thyroid medication