Understanding the Primary Health Risks of Grocery Store Tuna
When consuming tuna, whether fresh or canned from the grocery store, there are a few primary health concerns that consumers should be aware of. These are not typically issues that make tuna outright unsafe, but rather factors that necessitate moderation and proper preparation to mitigate risk. The most prominent concerns involve mercury, histamine, and in the case of raw preparation, parasites.
The Mercury Concern: Why it Varies by Tuna Type
Mercury is a naturally occurring element that enters our oceans from both natural events and human pollution, such as the burning of fossil fuels. Once in the water, it is converted into a more toxic form, methylmercury, by bacteria. This compound is then absorbed by small fish, which are subsequently eaten by larger predatory fish, like tuna. Because mercury accumulates up the food chain, larger and older tuna species tend to have higher concentrations than smaller ones.
This is the critical reason for the distinction between different types of canned tuna available in grocery stores:
- Albacore ("White") Tuna: This variety comes from larger, longer-living tuna species and generally contains significantly more mercury than lighter varieties. According to Consumer Reports testing, albacore products can have three times more mercury than light tuna. The U.S. Food and Drug Administration (FDA) recommends that pregnant or breastfeeding women and children limit their intake.
- Light Tuna (Skipjack): Sourced from smaller, younger tuna species like skipjack, canned light tuna has much lower mercury levels. It is considered a "best choice" for sensitive populations, though moderation is still key.
Even with light tuna, it is important to remember that mercury levels can vary unpredictably from can to can, a factor noted by Consumer Reports. This variability emphasizes the importance of following recommended consumption limits for all individuals, especially vulnerable groups.
Histamine Poisoning and Safe Handling
Another risk, particularly with fresh tuna, is histamine poisoning (scombroid poisoning). This occurs when tuna and other fish from the scombroid family are improperly handled and stored, allowing bacteria to grow and produce high levels of histamine. Histamine is not destroyed by cooking, so proper temperature control is essential from the moment the fish is caught until it is consumed. Symptoms of histamine poisoning can include flushing, sweating, headaches, and dizziness. To prevent this, always purchase fresh tuna from reputable sources that maintain strict temperature controls. Opened cans of tuna also require proper refrigeration and should be consumed within a few days.
Parasites and the Importance of Cooking or Freezing
While canned tuna is thoroughly cooked and sterilized during the canning process, eliminating the risk of parasites, fresh grocery store tuna is a different story. Raw or undercooked fish, including fresh tuna steaks, can harbor parasites. The FDA provides guidelines for freezing fish to kill parasites, and many restaurants and high-end markets follow these standards for "sushi-grade" fish, though the term itself is not legally regulated. For home cooks, thoroughly cooking tuna is the surest way to eliminate this risk.
Comparison Table: Canned Tuna vs. Fresh Tuna Steaks
| Feature | Canned Tuna (Light) | Canned Tuna (Albacore) | Fresh Tuna Steaks |
|---|---|---|---|
| Processing | Cooked and pressure-sealed at high heat, making it sterile and shelf-stable. | Cooked and pressure-sealed at high heat, making it sterile and shelf-stable. | Typically sold raw and previously flash-frozen; requires cooking or proper handling for raw consumption. |
| Mercury Levels | Significantly lower due to use of smaller, younger tuna (e.g., skipjack). | Higher due to use of larger, older tuna. | Variable, depending on the species (e.g., bigeye is higher). |
| Mercury Variability | Potential for unpredictable spikes in some individual cans, but generally low average. | High variability, with average levels substantially greater than light tuna. | Varies by species and location of catch; larger species have higher levels. |
| Histamine Risk | Minimal risk in unopened, properly stored cans. Increases upon opening and improper storage. | Minimal risk in unopened, properly stored cans. Increases upon opening and improper storage. | Higher risk if not properly refrigerated and handled from capture to cooking. |
| Parasite Risk | Negligible, as the canning process eliminates parasites. | Negligible, as the canning process eliminates parasites. | Present in uncooked or undercooked fish unless specifically frozen to FDA standards. |
| Recommended Intake | 2-3 servings per week for non-vulnerable adults. | 1 serving per week for non-vulnerable adults. | Depends on the species and an individual’s overall fish consumption. |
Expert Recommendations for Safe Tuna Consumption
Following expert recommendations is the best approach to enjoying tuna safely while mitigating health risks. The FDA and Environmental Protection Agency (EPA) provide guidelines, especially for vulnerable populations.
- For the general population: Healthy adults can consume moderate amounts of canned tuna as part of a balanced diet. Varying your fish intake to include low-mercury options like salmon, sardines, and tilapia is a smart strategy to reduce overall mercury exposure.
- For vulnerable groups (pregnant or breastfeeding women, young children): These individuals are more susceptible to mercury's effects and should exercise greater caution. It's recommended to choose light tuna (skipjack) and limit intake to 2-3 servings per week, while some experts suggest avoiding tuna entirely due to unpredictable mercury spikes. Alternative omega-3 sources are also excellent options.
How to Choose and Handle Tuna Safely
- Read the Label: When buying canned tuna, look for "light" tuna, as it is lower in mercury than "white" or "albacore" tuna. Some brands, like Safe Catch, also advertise that they test every tuna for mercury, offering another layer of assurance.
- Inspect Fresh Tuna: Look for fresh tuna that is properly refrigerated, has a fresh smell, and a bright, firm appearance. Avoid fish that has a strong odor or appears discolored.
- Check Can Integrity: Always check canned tuna for damage before purchasing. Avoid any cans that are dented, bulging, or leaking, as this can indicate potential contamination.
- Practice Proper Storage: Once opened, transfer canned tuna to an airtight, non-metallic container and refrigerate. Consume refrigerated leftovers within 3-4 days. Fresh tuna should be stored in the coldest part of your refrigerator and cooked or frozen promptly. For more information on seafood handling, visit the FDA website.
- Cook Fresh Tuna Thoroughly: If you're not purchasing explicitly handled-for-raw-consumption fish from a reputable source, cooking fresh tuna thoroughly is the safest way to eliminate parasites.
Conclusion: Safe Consumption is About Smart Choices
Is grocery store tuna safe to eat? Yes, but with some important caveats. By being mindful of the type of tuna you choose, the frequency of consumption, and proper handling procedures, you can enjoy the nutritional benefits of tuna while minimizing potential health risks. Choosing canned light tuna and limiting more mercury-laden varieties, particularly for sensitive populations, is a simple and effective strategy. Always purchase from reputable sources and adhere to proper storage and cooking methods to ensure a safe and delicious meal.
