Canned tuna is one of the most convenient and nutritious foods available. It's affordable, high in protein, and widely used in healthy meal plans. However, tuna can contain mercury, a heavy metal that builds up in fish over time.
The good news is that tuna can still be part of a healthy diet--the key is choosing the right type and eating it in moderation.
Why Mercury Is Found in Tuna
Mercury enters the ocean from natural sources and human pollution. Once in the water, it moves through the food chain. Here's how it happens:
1. Small fish absorb mercury from water.
2. Larger fish eat many small fish.
3. Predatory fish like tuna accumulate higher mercury levels over time.
This process is called bioaccumulation.
High mercury exposure can affect the nervous system, especially in:
* Pregnant women
* Babies and young children
* People who eat large amounts of high-mercury fish
Mercury Levels by Tuna Type
Not all tuna contains the same amount of mercury.
| Tuna Type | Mercury Level | Typical Use |
|---|---|---|
| Light Tuna (skipjack) | Low | Most Canned Tuna Products |
| Albacore (white tuna) | Moderate | Often Labeled "Solid White Tuna" |
| Bigeye Tuna | Higher | Common in sushi or premium tuna |
Key Point:
Light tuna generally contains about one-third the mercury found in albacore tuna.
Safe Weekly Tuna Amounts
According to U.S. health agencies, these intake levels are considered safe:
Adults*
* Light tuna: 2-3 servings per week
* Albacore tuna: About 1 serving per week
Pregnant or Breastfeeding Women*
* Light tuna: Up to 2 servings per week
* Albacore tuna: 1 serving or less
*Serving Size: About 4 ounces (113 grams).
How Mercury Affects the Brain
Mercury in fish is usually found as methylmercury, a form that is easily absorbed by the body. Once inside the body, mercury:
* Crosses the blood-brain barrier
* Damages neurons
* Interferes with normal brain signaling
Possible Symptoms of High Mercury Exposure
* Tingling or numbness
* Memory problems
* Vision or coordination issues
* Tremors
* Mood changes
In developing brains (fetuses and children), mercury exposure may affect:
* Learning ability
* IQ
* Attention
* Motor skills
This is why health agencies recommend stricter limits for pregnant women and children.
Does Draining or Rinsing Tuna Reduce Mercury?
No.
Mercury is stored inside the muscle tissue, not in the oil or water inside the can.
What draining or rinsing does:
* Reduces sodium
* Removes some surface salt
* Does NOT reduce mercury
The only ways to reduce mercury intake are:
* Eat smaller tuna species
* Limit how often you eat tuna
* Rotate with other types of fish
Fish With Much Lower Mercury
These alternative seafood options are generally low in mercury and rich in omega-3 fatty acids:
* Salmon
* Sardines
* Anchovies
* Pollock
* Shrimp
These can often be eaten more frequently than tuna.
Canned Tuna Brands Known for Lower Mercury (Generally)
Some companies test or select tuna with lower mercury levels than typical canned tuna.
Safe Catch
* Claims every fish is mercury-tested
* Mercury levels often below FDA limits
Wild Planet
* Uses smaller skipjack tuna
* Smaller fish typically contain less mercury
American Tuna
* Uses pole-caught albacore
* Often smaller fish than typical albacore
General Rule:
Choose skipjack or light tuna whenever possible, and avoid eating albacore every day.
Benefits of Canned Tuna
Despite mercury concerns, tuna remains a highly nutritious food when eaten in moderation. Benefits include:
* High-quality protein
* Omega-3 fatty acids
* Vitamin D
* Vitamin B12
* Selenium
* Low in fat and calories
When eaten responsibly, tuna can support heart health, muscle maintenance, and overall nutrition.
Tips to Reduce Mercury Risk
Follow these simple steps to keep tuna consumption safe:
* Choose light tuna more often than albacore
* Avoid eating tuna every day
* Rotate with low-mercury fish
* Pay attention to portion sizes
* Follow recommended weekly limits
Simple Takeaway
* Tuna is healthy and nutritious, but should be eaten in moderation.
* Light (skipjack) tuna is the safest choice for regular consumption.
* High mercury exposure usually happens only when large amounts of high-mercury tuna are eaten frequently.
Occasional tuna consumption is generally safe and can be part of a balanced, healthy diet.