Shark meat is consumed in many parts of the world, especially in Asia and Europe. However, there are concerns that eating shark meat may expose people to high levels of toxins like mercury. This article examines whether eating shark meat is safe or if it poses health risks.
Quick Answers
– Shark meat does contain mercury, but levels vary by species. Large, predatory sharks tend to have higher mercury levels.
– For most people, eating moderate amounts of shark meat does not cause mercury poisoning. However, frequent consumption over long periods may put people at risk.
– Pregnant women, nursing mothers, and young children are advised to avoid eating shark meat due to greater sensitivity to mercury exposure.
– Proper cooking and preparation of shark meat can reduce up to 50% of the mercury content.
– Regulations around shark fishing and sales differ globally. Some countries monitor mercury levels and restrict consumption for vulnerable groups.
Why Do Sharks Contain Mercury?
Sharks accumulate mercury in their tissues over their long lifespans. The major route of exposure is through their diet.
Bioaccumulation Through the Food Chain
Sharks are apex predators, sitting at the top of the marine food chain. They consume large fish, marine mammals, and seabirds that have accumulated mercury through their own diets.
The mercury builds up in the shark’s tissues through a process called bioaccumulation. Each step in the food chain leads to higher mercury concentrations. So apex predators like sharks tend to have very high levels of mercury compared to other fish species.
Long-Lived Species
Sharks have long lifespans, often living for decades or even centuries in some species. Their longevity allows mercury to accumulate in their bodies over time. The older and larger the shark, the higher the expected mercury levels.
Some shark species only reach maturity at 20-30 years old. They have had decades to bioaccumulate mercury from their prey before humans catch and eat them.
Methylmercury Exposure
Sharks primarily accumulate methylmercury, the highly toxic organic form. Methylmercury is absorbed and binds to proteins in animal tissue.
It cannot be easily cleared from the body and biomagnifies through food chains. This makes methylmercury the most concerning source of mercury exposure for humans.
Health Risks of Eating Shark Meat
Consumption of meat with high mercury levels presents a health hazard for humans. Here are the main concerns with eating shark meat:
Effects of Mercury Poisoning
Mercury is a potent neurotoxin. Consuming shark meat with very high mercury concentrations can cause mercury poisoning.
Symptoms include sensory disturbances, lack of coordination, and tunnel vision. In severe cases it may lead to respiratory failure, kidney damage, and even death.
Long-Term Low-Level Exposure
Regularly eating shark meat with lower mercury levels may still pose risks from gradual mercury accumulation.
Chronic low doses of mercury can impair brain development in children. It may also increase heart disease risk and negatively affect vision, memory, and immune function in adults.
Harmful Effects During Pregnancy
Pregnant women are considered the most sensitive population. Methylmercury can cross the placenta and affect the developing fetus.
Prenatal mercury exposure is linked to cognitive deficits, impaired motor function, and adverse effects on vision and hearing during childhood. Consuming shark meat during pregnancy is not advised.
| Population | Health Risks from Consuming Shark Meat |
|---|---|
| Pregnant Women | Impaired neurological development in fetus |
| Nursing Mothers | Mercury passed to infants through breast milk |
| Young Children | Neurodevelopmental disorders |
| Adults | Neurological disturbances, cardiovascular disease |
Mercury Levels in Different Shark Species
Mercury concentration varies greatly between shark species. Factors like habitat, diet, and lifespan influence mercury uptake.
Pelagic shark species that traverse open oceans generally have higher mercury levels than coastal shark species. Large predators contain more mercury than smaller shark species lower on the food chain.
Here are typical mercury concentrations for some commonly consumed shark species:
| Shark Species | Average Mercury Concentration (parts per million) |
|---|---|
| Blue shark | 1.32 ppm |
| Tiger shark | 3.58 ppm |
| Bull shark | 1.95 ppm |
| Hammerhead shark | 2.55 ppm |
| Mako shark | 4.54 ppm |
| Thresher shark | 2.85 ppm |
| Spiny dogfish | 0.66 ppm |
For reference, many guidelines recommend less than 0.5 ppm mercury for vulnerable groups like pregnant women and children. Levels over 1 ppm are considered unsafe for regular consumption.
Safe Consumption Recommendations
Adhering to seafood consumption advisories can reduce mercury exposure from eating shark meat. Recommendations may vary between countries but general guidelines include:
Avoid Eating Shark Meat (Vulnerable Groups)
– Pregnant and breastfeeding women
– Women planning pregnancy within the next year
– Children under age 12
These populations should avoid shark meat altogether or eat only once per month.
Maximum Recommended Intake (General Population)
– Men: 1 serving shark meat per week
– Women age 12-45: 1 serving shark meat per week
– Women over 45 and teens: 2 servings shark meat per month
One serving is around 4 ounces or 120 grams. Consuming more than the recommended amount substantially increases risk.
Favor Smaller Coastal Shark Species
Small sharks like Atlantic sharpnose, blacktip, and bonnethead have lower mercury levels. Prioritizing these species can reduce mercury exposure.
Ways to Reduce Mercury in Shark Meat
Proper handling and preparation of shark meat can decrease mercury content by up to 50%:
Remove Skin, Fat, and Organs
Mercury concentrates in shark liver, kidney, skin, and adipose tissue. Removing these parts reduces the amount consumed.
Marinate the Meat
Marinating shark fillets in acids like lemon, lime, or vinegar helps draw mercury out of the tissue. Rinsing well after marinating removes more mercury.
Cook Thoroughly
Heating protein causes it to denature and release mercury into cooking liquid. Cook shark meat to an internal temperature of at least 145°F (63°C).
Discard Cooking Liquid
Mercury leaches into cooking liquids like oil or broth. Properly disposing of the liquid reduces mercury intake from the meal.
Global Regulation of Shark Meat
Some regions have enacted regulations to protect consumers from mercury exposure when eating shark meat:
European Union
– Has capped mercury levels in all fish at 1 ppm
– Requires warning labels if mercury exceeds 0.5 ppm
– Pregnant women advised to avoid shark meat
United States
– Shark meat not directly regulated
– Advisories limit intake for vulnerable groups
– FDA testing finds mercury >1 ppm in some species
Canada
– Shark meat sales must meet <0.5 ppm mercury limit - Health Canada advises children and pregnant women to avoid
Australia
– Food Standards code limits mercury to 1 ppm
– Australian guidelines say pregnant women should not eat shark
Japan
– No national regulations on shark meat specifically
– General guidance to limit consumption of large predatory fish
Conclusion
Eating shark meat comes with a degree of risk from mercury exposure. Certain groups like pregnant women and children should avoid shark meat completely due to sensitivity. For most adults, moderate consumption of lower mercury shark species may be safe. However, frequent or excessive intake is not advised. Regulations, advisories, and proper handling can help reduce potential health hazards from the mercury content in shark meat.
