What is Flake and Why Does It Contain Mercury?
The Link Between Shark Meat and the Name 'Flake'
For many, especially in Australia, the term 'flake' is synonymous with a boneless fillet of white fish, a staple in traditional fish and chip shops. However, most people do not realize that 'flake' is not a species of fish at all, but rather the commercial name for the flesh of various shark species. While the Gummy shark is the most common species used, other species like the School shark and Sawshark can also be marketed as flake. This labeling practice is significant because it directly impacts the mercury content, as sharks are at the top of the marine food chain and their biological makeup is different from that of smaller, bony fish.
The Process of Bioaccumulation
The reason does flake contain mercury is primarily due to a natural process called bioaccumulation. Here’s how it works:
- Mercury in the Environment: Mercury is released into the environment from natural sources and human activities, such as the burning of fossil fuels. It then settles in water bodies.
- Uptake by Microorganisms: Once in the water, microorganisms absorb the mercury, converting it into a more toxic organic form called methylmercury.
- Climbing the Food Chain: Small fish consume these mercury-laden microorganisms. As larger predatory fish, like sharks, eat these smaller fish, the methylmercury accumulates and concentrates in their flesh over their long lifespan.
- Apex Predator Effect: As apex predators, sharks are at the top of this food chain, meaning they consume a high volume of other fish, leading to the highest concentration of mercury in their bodies.
The Forms of Mercury in Fish
It's important to understand that the mercury found in fish is primarily methylmercury, a highly toxic form that is readily absorbed and can be harmful to human health. Unlike other contaminants that may be present on the surface, methylmercury is bound to the proteins within the fish's tissue, which means it cannot be removed through simple cooking or preparation methods. This highlights the importance of limiting consumption rather than relying on cooking techniques to mitigate risk.
Health Risks and Recommended Consumption
Understanding Mercury Toxicity
For the general population, the amount of mercury consumed through a moderate intake of fish is generally not a health concern, and the benefits of eating fish often outweigh the risks. However, high levels of mercury exposure can lead to serious health issues. The central nervous system is particularly vulnerable to the effects of methylmercury, and excessive exposure can cause neurological damage.
Recommended Limits for Vulnerable Groups
For certain sensitive groups, mercury intake is a significant concern because their developing nervous systems are particularly susceptible to harm. Therefore, health authorities, such as Food Standards Australia New Zealand (FSANZ), provide specific, stricter consumption guidelines for these individuals:
- Pregnant and Planning-to-Conceive Women: A developing fetus is highly vulnerable to methylmercury. FSANZ recommends that these women consume no more than one 150g portion of shark (flake) per fortnight, and no other fish should be eaten during that period.
- Breastfeeding Women: As mercury can be passed to the infant through breast milk, similar precautions are often recommended to protect the infant.
- Young Children (under 6 years): Due to their smaller body size and developing nervous systems, children should also follow the same fortnightly limit for high-mercury fish as pregnant women.
General Population Guidelines
For all other individuals, a more lenient, yet still cautious, approach is advised. The general population is typically advised to limit their intake of high-mercury fish like shark (flake) to one 150g portion per week, and to not consume any other fish during that same week. Diversifying fish choices is a key strategy to ensure nutritional benefits without excessive mercury intake.
Flake vs. Other Seafood: A Mercury Comparison
When making dietary choices, understanding the relative mercury levels in different types of seafood is crucial. The following table provides a comparison to help inform your decisions.
| Fish Type | Common Mercury Level | Example Recommendation | Dietary Considerations |
|---|---|---|---|
| Flake (Shark) | High | Max 1 portion per week for general population; max 1 portion per fortnight for vulnerable groups. | High risk, limited intake necessary. |
| Swordfish/Marlin | High | Similar limits to flake; max 1 portion per week or fortnight depending on population. | High risk, limited intake necessary. |
| Orange Roughy | High | Max 1 portion per week for vulnerable groups. | High risk, limited intake necessary. |
| Canned Tuna (smaller species) | Lower | Safe for regular consumption for most, though some guidelines advise moderation. | Good, lower-mercury alternative. |
| Salmon | Low | Generally safe for regular, multiple weekly servings. | Excellent low-mercury choice. |
| Sardines | Low | Generally safe for regular, multiple weekly servings. | Excellent low-mercury choice. |
Tips for a Balanced and Safe Seafood Diet
To enjoy the nutritional benefits of seafood while managing mercury risk, follow these best practices:
- Diversify Your Fish Choices: Instead of relying on one type of fish, include a variety of species in your diet. This naturally minimizes your exposure to any single contaminant, including mercury.
- Choose Smaller, Shorter-Lived Fish: Opt for smaller fish like salmon, trout, sardines, and herring. These species are lower on the food chain and generally accumulate less mercury.
- Eat in Moderation: Even with low-mercury fish, moderation is key to a balanced diet. Pay attention to portion sizes and the frequency of consumption.
- Consult Health Guidelines: Always refer to the latest food safety advice from national health authorities, such as Food Standards Australia New Zealand (FSANZ) or your local health department, for the most up-to-date recommendations.
- Be Mindful of Labeling: If buying pre-packaged fish, read labels carefully. If a fish is labeled as 'flake', be aware that you are consuming shark meat with the associated mercury levels.
- Outbound Link: For further detailed information and the latest advisories on mercury in fish, consult the official guide from Food Standards Australia New Zealand.
The Broader Context of Mercury Contamination
Mercury contamination is a global issue resulting from environmental pollutants. While it's important for consumers to be aware of and manage their personal intake, it is also a reminder of the broader need for environmental stewardship and regulation. Initiatives to reduce mercury emissions from industrial sources are critical to protecting marine ecosystems and, by extension, our food supply.
Conclusion
In short, yes, flake contains mercury because it is the flesh of shark, an apex predator that accumulates high levels of the metal through the marine food chain. For the general population, moderate consumption of flake is manageable with careful portion control. However, for sensitive populations such as pregnant women, young children, and those planning pregnancy, flake should be strictly limited or avoided due to the potential for harmful neurological effects. By diversifying your seafood choices and opting for smaller, lower-mercury species like salmon and sardines, you can enjoy the nutritional benefits of a seafood-rich diet while minimizing your health risks. Staying informed about which fish to limit is the best way to ensure a safe and nutritious diet for you and your family.
