How safe is Canned Fish

Although heavy metals could give rise to health risks, the biggest problem related to canned fish revolves around the amount of mercury/ methyl mercury found in the canned fish.
In relation to canned fish, lab tests are not conducted in Sri Lanka.
No research has been conducted in Sri Lanka so far with regard to the adverse health implications of consuming canned fish
Canned fish is the ready-to-eat, convenient choice of food for anyone who loves to indulge in the tempting fish cutlet, for those planning to whip up a quick meal or simply for anyone who loves fish. Canned fish such as Tuna, Mackerel and Sardines are believed to be enriched with the high nutritious value of Omega 3 fatty acids that are quintessential to cut down on cardiovascular diseases, fight back depression and improve brain health and thereby to improve one’s overall well-being. However, experts harbour different opinions with regard to the various health implications of over consuming canned fish due to the heavy metal content such as methyl mercury found in canned fish. Enlightening us on the subject further, several experts shared their expert opinion with Dailymirror concerning the benefits and adverse effects of consuming canned fish.

“Sri Lanka needs to have a proper regulatory body to test fish for heavy metals” – Hemantha Withanage

Expressing his views on the subject, Executive Director of the Centre for Environment Justice and Environmental Activist Hemantha Withanage affirmed that canned fish definitely contains certain heavy metals given the fact it is also stored in a metallic can. “To my knowledge, no research has been conducted in Sri Lanka so far with regard to the adverse health implications of consuming canned fish and on how marine pollution has an adverse effect on canned fish.

However, we conducted a survey in the Negombo Lagoon area; both at the lagoon fishery and with regard to the Seer Fish caught by trawler boats in the area. During our survey, we identified small fish that contained high levels of mercury in them. Samples of human hair also indicated that 4.77 µg of mercury were found in them. Usually Sword Fish and Seer Fish are exported to the European market from Sri Lanka. However, if tests by European regulatory bodies indicate that there are heavy metals in these fish, such fish are then not permitted to be sold in the market. Although mercury levels evident in canned fish have not been a serious issue in the context of Sri Lanka, it is time that our country also has similar regulatory bodies in place to test the quality and freshness of the fish sold to our consumers” Withanage said.

“Extracting fish oil from its primary source is the best way to avoid heavy metals” – Dr. Waruna Gunathilake

Explaining on how our food chain is concentrated with high levels of heavy metals, Dr. Waruna Gunathilake, Consultant Physician and Head of the Toxicology and National Poisons Information Centre at the National Hospital of Colombo,Sri Lanka said that canned fish could be very useful although it is not always the healthy option available. This is mainly because canned fish contains a very high level of sodium which could give rise to health risks such as high blood pressure.

“We should be careful when consuming canned fish because consumers are not aware of the source or origin, from where the fish are harvested. Fish can easily get poisoned with heavy metals due to water pollution. This is not the case only for canned fish but also for fresh fish. Most importantly, it should be noted that there is a significant threat of heavy metals entering the human body through the food chain. Consumers are usually not aware whether the fish is harvested from shallow water or deep sea water or if the fish is obtained from a polluted water source that is contaminated with heavy metals. Apart from the salted water, canned fish may contain a lot of other ingredients such as tomato sauce and other flavour enhancers such as food additives, preservatives, colouring or pigmentation.

Therefore, it is important to ensure that canned fish is labelled with the ingredients and the origin of the fish clearly mentioned.

Although heavy metals could give rise to health risks, the biggest problem related to canned fish revolves around the amount of mercury/ methyl mercury found in the canned fish. Our food chain gets contaminated with heavy metals like mercury through fish owing to the pollution of sea water and fresh water. These heavy metals get concentrated in the food chain according to the ascending order; thus the amount of heavy metals in fish would be very high by the time it reaches the consumer.

Apart from the canned fish we consume often, people also tend to consume fish oil as a means of obtaining more nutrition for the body. However, the majority in the pharmaceutical industry today have resorted to extracting fish oil from its primary source such as through algae, sea planktons and aquatic plants instead of obtaining fish oil from the fish. This is mainly because extracting fish oil from its primary source is one of the best ways to avoid the increased levels of heavy metal found in fish. However, it should be noted that this is still a debatable topic in the scientific circle,” Dr. Gunathilake said.

“Fish such as groupers and sardines caught from coastal areas are definitely affected from coastal pollution” – Dr. Terney Pradeep Kumara

Commenting further, General Manager of the Marine Environment Protection Authority and Former Head of the Department of Oceanography and Marine Geology, University of Ruhuna, Dr.Terney Pradeep Kumara said that canned fish such as Tuna fish are often caught from offshore areas and not from shallow water or coastal areas. He said that these kinds of fish are not much affected directly by coastal pollution. For instance fish such as groupers and sardines caught from coastal areas are definitely affected from coastal pollution unlike Tuna caught from the ocean. “The coastal pollution mainly occurs due to sewage, agro-chemicals, pharmaceutical residuals and plastic-polythene and micro plastic that are released to the water. For instance, the pharmaceutical residual and agro-chemicals are the main chemicals which get bio-magnified. Bio magnification refers to an instance where the chemicals are consumed by a fish. If this fish is consumed by another big fish, the predator will accumulate ten times more concentrated toxicants into the body compared to its prey.

Therefore, if we consume a carnivore fish the possibility of getting contaminated with a high dose of toxins is greater compared to when we consume an herbivore fish. However, it is not a practical approach to distinguish between carnivore and herbivore fish when purchasing fish from the market. These fish could be contaminated with heavy metals or inorganic compounds. To date, no one has conducted any research on the Sri Lankan context with regard to the coastal pollution’s effect on fish and the contaminated fish’s impact on human health” Dr. Kumara said.

When inquired whether any action has been taken against the coastal pollution in Sri Lanka, he said that the Marine Environment Protection Authority has taken measures to observe the quality or parameters of water especially in public beach areas. He said that their analysis indicates that almost all the beaches are polluted especially with E. coli bacteria found in sewage water. “We found that the water is also polluted with fecal matter. In fact hotel waste, canals and rivers are all contaminated to a certain extent, which has given rise to coastal and lagoon water pollution. However, it should be noted that the deep ocean fish are not affected by this pollution. Increased awareness is the key to bring this water pollution under control” Dr. Kumara added.

“We are not aware if the canned fish that is imported to Sri Lanka is tested for Bisephenol A” – Dr. Ruwan Wijayamuni

Speaking to Daily Mirror, Chief Medical Officer of the Colombo Municipal Council Dr. Ruwan Wijayamuni shared his views concerning the benefits and risks involved with over-consuming canned fish. He said that in relation to canned fish, lab tests are not conducted in Sri Lanka. However, he stressed the importance of ensuring that stringent standards are maintained in the processing and canning procedure of canned fish. “Basically, when we talk about canned fish, the most common canned fish we find in the Sri Lankan market is tuna, sardine and mackerel. Also there can be red salmon. These are the commonest types of canned fish that we find. However, in our part of the world, even tuna is not very popular

. Our consumers tend to have a greater preference for sardines and mackerel than for tuna. The mackerel fish is not found in the Indian Ocean. It is found in areas around the Pacific Ocean. That is why our fish canning industry has relatively failed since we do not have the required fish resources. Basically, canned fish is not a bad health option because it gives a lot of protein. Also, the bone part of the canned fish is very soft as a result of the very high temperature and high pressure applied on it. So the bones become very soft and are easily edible unlike the ordinary fish bones.

These fish bones are a rich source of calcium and protein. Therefore, canned fish is generally considered as a very good source of protein and calcium for people. Canned fish is also an excellent source of Omega 3 fish oil which is really beneficial for the cardiovascular system and to lower the level of bad cholesterol in the body. These are the benefits of consuming canned fish” Dr. Wijayamuni said.

“However there are certain health risks involved with consuming canned fish. Firstly, canned fish should be processed in the correct manner. Secondly, it should be canned in a proper container. The processing mechanism and the container in which the fish is stored are very important elements that should be taken into account by canned fish manufacturers. Usually, the fish is canned in a low acidic media that is higher than the value of 4.5 pH. Therefore, this is not a great level of acid concentration where microorganisms or bacteria are killed. So there is a great potential that microorganisms could still thrive in the canned fish since fish blood and intestines could still contain certain microorganisms. Canned fish could also be a carrier of micro elements such as mercury.

It could also contain radioactive elements mainly due to undersea bombing/nuclear testing. These radioactive elements have a high potential of being absorbed by fish flesh. This is why it is not advisable to over consume canned fish. However, canned fish has become a common food between middle income, lower middle income and lower income people.

Canned fish could also contain lots of spores present in their inactive form and the outer layer of these spores act as a protective layer for bacteria when the bacteria is encountered with unfavourable grounds. Therefore, it is vital that heat and pressure should be applied in a proper manner to kill the bacteria found in fish. There are also views put forward in the scientific circle that the outer lining of the can is coated with Bisephenol A (BPA) – applied inside the can as a coating. Acidic reactions may sometimes occur when the chemical coating comes into contact with the lower acidic solution in which the fish is generally immersed. It should be noted that these chemicals will not be destroyed during cooking. Therefore, it could affect the immune system and metabolism while giving rise to hypertension mainly due to the high salt or sodium concentration evident in canned fish.

While research is currently being done with regard to these factors, it should be noted that countries like Canada including a few states like the U.S. have banned the coating of tin containers with Bisephenol A. However, we are not aware if the canned fish that is imported to Sri Lanka is tested for Bisephenol A” he further explained. Dr. Wijayamuni said that most canned fish is consumed readily and is not cooked before consumption. According to him, if by chance canned fish is contaminated with bacteria, it could enter one’s body unless necessary precautions are taken to cook it properly.

“Decades ago, there was a very nasty pathogen known as Clostrivium Botulini that was present in canned fish. This could produce a neuro toxin that affects an individual’s nerves. Canned fish initially came into the scene during World War 1 and became very popular by the time of World War 11. At the early stages, the presence of Clostrivium Botulini in canned fish resulted in giving rise to deaths among its consumers. The very first symptoms of Botulism are related to the blurring of vision, loss of consciousness, confusion, lack of coordination, affects the optic nerve system and could even result in death. Consumers should be very careful when purchasing canned fish. Disfigured or bloated cans should be avoided and if a consumer comes across such a can, he or she must immediately bring it to the notice of the shop owner” he added.

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