Canned tuna is a go-to meal for many—affordable, rich in protein, and incredibly convenient. But what if your favorite tuna sandwich was quietly putting your health at risk? That everyday pantry staple could be hiding a serious concern: mercury contamination.
Mercury is a hazardous heavy metal that can seriously damage the nervous system, especially with repeated exposure. What’s more alarming is that not all canned tuna is the same—certain types carry far higher mercury levels than others. Without realizing it, you could be regularly consuming dangerous amounts.
Let’s take a closer look at what mercury is, why it ends up in tuna, and how to make safer choices without giving up this nutritious food.
What Is Mercury and Why Does It End Up in Tuna?
Mercury exists naturally in the Earth, but industrial practices like mining and burning coal have released excessive amounts into our environment. This mercury eventually makes its way into oceans, where it’s transformed into methylmercury—a highly toxic form.
This substance accumulates in marine life, especially in large predator fish like tuna. The process is called bioaccumulation: small fish absorb the mercury from water, larger fish eat those fish, and so on up the food chain.
By the time it reaches tuna—and eventually, your plate—mercury levels can be alarmingly high.
Over time, regular mercury exposure can harm the brain and nervous system. Pregnant women, children, and people with heart or neurological concerns are especially vulnerable.
One Key Mistake Most People Make
The most common error? Not knowing the differences between tuna varieties. Not all canned tuna is created equal, and the type you choose has a huge impact on how much mercury you ingest.
Here are the three main types:
- Skipjack Tuna: This smaller species is usually labeled as “light tuna.” It has the lowest mercury levels—about 0.12 parts per million—making it the safest option for regular consumption.
- Yellowfin Tuna: Slightly larger, yellowfin contains higher mercury levels (around 0.35 ppm). While not as high as albacore, it should be eaten in moderation.
- Albacore Tuna: This is the highest in mercury, averaging up to 0.50 ppm. Health authorities recommend significantly limiting how often you eat it.
Tip: If the can doesn’t specify the species, it’s likely skipjack. Always read the label to be sure.
Other Tuna Mistakes to Avoid
Besides species confusion, here are three more common slip-ups when consuming canned tuna:
Ignoring Labels: Skipping over the fine print can mean missing important health information. Some brands are more transparent about mercury content than others, so a quick online check can be worth your time.
Overconsumption: Tuna is healthy in moderation, but eating too much can lead to mercury buildup. Experts suggest limiting total seafood intake to about 8 ounces (227g) per week, especially for those at higher risk.
Not Draining Properly: Whether your tuna is packed in oil or water, draining it thoroughly prevents soggy meals and helps reduce contaminant intake. Use the lid or a strainer for best results.
Tuna in Oil vs. Tuna in Water: What’s Safer?
This might surprise you: tuna in oil could actually reduce mercury exposure. Mercury binds to fats, so when you drain the oil, you discard some of the metal with it.
Tuna in oil also tends to be richer in omega-3s and vitamin D, though it’s higher in calories.
In contrast, tuna in water is leaner but may retain more mercury. So if mercury is your main concern, well-drained oil-packed tuna may be the smarter option.
How to Keep Tuna in Your Diet Safely
You don’t need to give up tuna entirely—just be smart about your choices:
- Stick to skipjack (light) tuna for routine meals.
- Always read labels and choose transparent brands.
- Rotate tuna with other low-mercury fish like salmon, sardines, trout, or mackerel.
- Follow serving size recommendations, especially for kids or pregnant women.
Final Thoughts
Canned tuna is still a valuable source of protein and essential nutrients. But understanding the risks of mercury—and knowing how to avoid them—empowers you to enjoy it safely.
The next time you’re shopping, take a moment to read the label and make a well-informed choice. Your health is worth the extra care.
