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Mercury and Omega-3 Oils in Australian Seafood

Mercury and Omega-3 Oils in Australian Seafood

MERCURY AND OMEGA-3 OILS IN AUSTRALIAN

Risks and benefits of seafood consumption

Levels of mercury in most Australian are low, and the benefits of seafood consumption outweigh the risks. Scientific evidence shows that mercury exposure is not an issue for the general Australian population.

June 2015 2 Risks from mercury in seafood

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Mercury is highly toxic to However, mercury with seafood consumption. With humans. Although inorganic accumulates in aquatic food regard to risks, it found that: mercury is poorly absorbed chains. Although all fish • there is convincing evidence by the human body, of adverse neurological contain small amounts of in aquatic environments can and neurodevelopmental convert inorganic mercury to mercury in their muscle tissue, outcomes in infants and methylmercury, which is readily higher amounts can be found young children associated absorbed. From the human gut, in predatory fish, long-living with mercury exposure during methylmercury enters the brain fish, and mammals such as fetal development due to of adults and fetuses, where it whales. Almost all human maternal fish consumption accumulates and is converted to during pregnancy exposure to mercury occurs inorganic mercury. • there is possible evidence via consumption of seafood of cardiovascular harm and The developing fetus, particularly (predominantly finfish). other adverse effects (for during the first trimester of example, immunological and pregnancy, is particularly A severe incident of mercury food reproductive effects) associated susceptible to the toxic effects of poisoning occurred in the region with mercury exposure. mercury. Dietary practices during of Minamata Bay in Japan during and immediately before pregnancy the 1950s, associated with both affect fetal exposure during the high levels of mercury in seafood first trimester. and high levels of consumption of the contaminated seafood. This Mercury that is absorbed as part incident made it clear that high of the diet can cause mental levels of dietary mercury in seafood retardation, cerebral palsy, impair the mental and physical deafness, blindness and motor

MERCURY AND OMEGA-3 OILS IN AUSTRALIAN SEAFOOD AUSTRALIAN IN OILS OMEGA-3 AND MERCURY development of young children speech disorders in individuals exposed during gestation. In who were exposed as fetuses, and Australia, a small number of cases sensory and motor impairment of mercury-related disease have in exposed adults. As well, occurred when children and their chronic, low-dose exposure of the parents have overconsumed fish as fetus to mercury from maternal a rice soup (‘congee’). consumption of contaminated fish has been associated with impaired In 2010, an Expert Consultation performance in neurobiological on the Risks and Benefits of Fish tests that measure attention, Consumption was established language, memory and fine-motor by the Food and Agriculture function. There is also evidence Organization of the United that exposure to mercury can affect Nations (FAO) and the World the cardiovascular system, causing Health Organization (WHO), at the heart disease, and problems with request of the Codex Alimentarius blood pressure regulation and Commission. It comprised heart rate. experts in nutrition, toxicology, epidemiology, dietary exposure Low levels of mercury are and risk assessment. The expert naturally present in the consultation concluded that both environment and in all foods. risks and benefits were associated 3 Benefits from omega-3 oils in seafood |

Fish contain long-chain omega-3 and young children when fish selenium, iodine, vitamin D, choline MERCURY AND OMEGA-3 OILS IN AUSTRALIAN SEAFOOD polyunsaturated fatty acids, is consumed by the mother and taurine) that may also provide including eicosapentaenoic acid before and during pregnancy health benefits. (EPA) and docosahexaenoic acid • other evidence suggests that fish Benefits to an infant’s neurological (DHA). These types of oils are consumption is likely to have a development from seafood important for normal , positive impact on some health consumption by the mother during and many claims have been made problems such as ischaemic pregnancy are reflected in increases about the benefits to human stroke, but that several other in the child’s IQ (intelligence health of dietary supplements health claims (such as impacts quotient). This is discussed containing them. on mood and depression, and further below. reduction of cancer) could In 2010, the FAO/WHO expert not be substantiated with With regard to cardiac death, consultation concluded that: current evidence. significant reduction in deaths • there is convincing evidence in Australia from coronary heart of beneficial health outcomes The experts concluded that the disease might be expected from from fish consumption through health benefits of fish are likely consumption of 3–4 serves per reduction in risk of cardiac to be largely due to long-chain week of seafood (serving size 150 g) death (from coronary heart omega-3 polyunsaturated fatty with moderate concentrations disease), and of improved acids. However, fish contain other (5 mg/g) of EPA plus DHA. neurodevelopment in infants nutrients (for example, protein,

Risks versus benefits of seafood consumption

The risks of seafood consumption associated with mercury contamination must be weighed against the benefits associated with omega-3 oils.

With regard to neurological development, the FAO/WHO expert consultation found that a child’s IQ was increased by an average of 4.0 points if their mother consumed 100 mg of DHA per day as part of a fish diet during gestation. The net gain in IQ was greatest when the seafood consumed was low in mercury and high in omega-3 oils. High mercury levels counteract the gain in IQ associated with seafood consumption.

The FAO/WHO expert consultation concluded that the benefits of seafood consumption outweigh any risks both for the general population and for women of childbearing age. It also found that advice to limit seafood consumption might be harmful to health for some groups.

Provided that at-risk groups (including pregnant women, women planning pregnancy and young children) consume only those seafoods containing less than 0.5 mg/kg of mercury, they will benefit from unrestricted consumption, particularly if fatty fish such as sardines and farmed or are part of the diet. 4

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Levels of mercury and omega-3 oils in Australian fish

Maximum recommended Maximum recommended Levels of mercury in levels of mercury in seafood dietary intake of mercury Australian fish

Standard 1.4.1 of the Australia The health standard for mercury in Surveys of Australian finfish have New Zealand Food Standards Australia follows the health-based found that levels of mercury in Code sets a maximum level (ML) guidance values established by the most Australian seafoods are low. for mercury in seafood. Australian Joint FAO/WHO Expert Committee Most commercially harvested seafoods are divided into two on Food Additives. This committee oceanic fish in Australia have categories: those with a mean has set a ‘tolerable weekly intake’ mercury levels of less than level of total mercury of less than level for methylmercury of 3.3 µg 0.5 mg/kg. However, individual 0.5 mg/kg and those with a mean per kilogram of body weight per sharks, particularly warm-water MERCURY AND OMEGA-3 OILS IN AUSTRALIAN SEAFOOD AUSTRALIAN IN OILS OMEGA-3 AND MERCURY level of total mercury of less than week (µg/kg/week) for the general sharks (from the Carcharinus 1 mg/kg.1 Fish in the latter category population and 1.6 µg/kg/week genus) and large game fish such (that is, containing higher levels of for the fetus. These values have as and marlin, can mercury) include gemfish, been adopted by Food Standards have mercury levels much higher (including marlin), southern bluefin Australia New Zealand (FSANZ). than the Food Standards Code , barramundi, ling, orange prescribed mean ML for a batch roughy, rays and all species of shark. of fish of 1 mg/kg. Although is a large predatory fish, it generally has 1 The ML is based on a mean level resulting from testing a prescribed number of samples. mercury levels less than 0.5 mg/kg. As well, only very low levels of mercury have been detected in Illness from eating seafood is rare. barramundi, even though it is For most people, following the listed within the higher-mercury FSANZ category. Crustaceans and recommended national dietary molluscs generally have very low guidelines is the best means of mercury concentrations. balancing risks and benefits. Species associated with elevated levels of mercury represent approximately 1.4% of the total seafood consumed in Australia. Gemfish, ling, , sharks and tuna account for 5

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MERCURY AND OMEGA-3 OILS IN AUSTRALIAN SEAFOOD

more than 25 million servings consumed seafood products in Levels of omega-3 oils in (serving size 150 g) per year in Australia. Only low concentrations Australian fish Australia. More than half of these of mercury were found in all servings comprise shark. However, samples, with a median ranging In Australian fish, for Australians consume around from 0.014 mg/kg in cooked species for which data are 1.8 billion servings of seafoods that prawns to 0.11 mg/kg in battered available, the highest levels are low in mercury, including finfish, fish fillets. of the long-chain omega-3 crustaceans and molluscs, and The Australian Total Diet Survey polyunsaturated fatty acids canned fish. found that seafoods were the EPA and DHA are found in Individuals who regularly consume major sources of mercury exposure farmed species (Atlantic large amounts of fish (particularly for all age groups. However, the salmon, ocean trout and types of fish with potentially data indicated that the estimated yellowtail kingfish). high mercury levels) could be dietary exposures to mercury for exposed to dangerous levels each age category were below the In these three species, combined of mercury. However, two risk tolerable weekly intake of 1.6 μg/kg concentrations of EPA and DHA assessments – one assessing the body weight for all age groups, have been found to range from risk from consumption of finfish and therefore within the health- around 18 mg/g to 31 mg/g. This in New South Wales and the other based guidance value. FSANZ compares with levels in Australian assessing the risk associated with concluded that: sardine of 6.3 mg/g, in gummy mercury in Australian seafood – Dietary exposure to methylmercury for shark of 1.3 mg/g and in banana have found that the potential risk all groups was below the respective prawn of 1–2 mg/g. from mercury is very low. This is reference health standard. On this basis, mainly because of a low likelihood In general, fish that have high levels there is no human health and safety of exposure to finfish with high of mercury – including marlin, risk with regard to current intakes of levels of mercury. swordfish and orange roughy methylmercury by Australian consumers. – have low levels of beneficial Most of the seafood consumed Due to the potential adverse effects of omega-3 oils. As a result, the risk in Australia (72% in 2008–09) is methylmercury on vulnerable population to benefit ratio is higher for these imported. The Australian Total groups, such as pregnant women and species. Conversely, fish such as Diet Survey, conducted by FSANZ young children, methylmercury will salmon, mackerels and sardines are in 2011, surveyed the levels of continue to be monitored in future high in omega-3 oils and low in mercury in battered fish fillets, studies. mercury, giving them a low risk to frozen fish portions, tuna canned benefit ratio. in brine and cooked prawns, which are some of the most commonly 6 Seafood consumption advice in Australia and

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A number of organisations around FSANZ advises that people can the world have studied maximum safely eat 2–3 serves a week of most safe levels of exposure to mercury, types of fish. Its advice notes that leading to recommendations on fish is low in saturated fat, high in the maximum advisable levels unsaturated fat and omega-3 oils, of seafood intake. Organisations and a rich source of iodine, and that have provided advice on that everyone, especially pregnant these issues include the United women, should regularly include States Environmental Protection fish in their diet. However, although Agency, the United States Food pregnant women, women planning and Drug Administration, the FAO, pregnancy and young children can the WHO, the Codex Alimentarius safely consume 2–3 serves of most Commission and the European types of fish and other seafood, Food Safety Authority. FSANZ advises that they should restrict their consumption of some Australia, New Zealand, species (see Table 1). Canada, Japan, Norway, Spain, the United Kingdom and the United States provide differing advice to consumers on seafood consumption. However, all these countries include recommendations on the number of weekly servings for pregnant

MERCURY AND OMEGA-3 OILS IN AUSTRALIAN SEAFOOD AUSTRALIAN IN OILS OMEGA-3 AND MERCURY women, small children and other consumers, and identify seafood that may contain high levels of mercury.

Table 1 Advice provided to Australian consumers by FSANZ

Recommended amounts Target group Species for consumption Pregnant women Any fish and seafood other than orange roughy 2–3 serves per week and women (sea ), , shark (flake) or billfish planning pregnancy (swordfish, broadbill, marlin) (1 serve = 150 g) Orange roughy (sea perch) or catfish and no other 1 serve per week Children up to fish that week 6 years OR (1 serve = 75 g) Shark (flake) or billfish (swordfish, broadbill, marlin) 1 serve per fortnight and no other fish that fortnight Rest of the Any fish and seafood other than shark (flake) or 2–3 serves population billfish (swordfish, broadbill, marlin) (1 serve = 150 g) Shark (flake) or billfish (swordfish, broadbill, marlin) 1 serve and no other fish that week 7 CONCLUSIONS |

Consumption of seafood is associated MERCURY AND OMEGA-3 OILS IN AUSTRALIAN SEAFOOD with both benefits and risks, although illness from eating seafood is rare. Risks associated with mercury in seafood are greater for some large species of fish (including sharks) and for some sections of the population (especially pregnant women and their fetuses, and young children). Mercury can cause neurological damage, particularly to the developing fetus. Benefits of seafood consumption are associated largely with long- chain omega-3 polyunsaturated fatty acids, which can reduce deaths from coronary heart disease, and improve neurodevelopment in infants and young children. Levels of mercury in most Australian seafoods are low, and the benefits of seafood consumption outweigh the risks. Evidence shows that mercury exposure is not an issue for the general Australian population. However, pregnant women should avoid consuming large amounts of the types of fish that are likely to contain higher levels of mercury. For most people, following the recommended national dietary guidelines is the best means of balancing risks and benefits. For more information or to view the full report relating to mercury in Australian seafood, please visit our website: www.safefish.com.au

SafeFish Secretariat GPO Box 397 Adelaide, South Australia 5001

Alison Turnbull – Program Manager E: [email protected] P: 08 8303 9623 M: 0418 348 450

Natalie Dowsett – Executive Officer E: [email protected] P: 08 8303 9399 M: 0407 604 027

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