Can you eat too much tuna?
Yes, it is possible to eat too much tuna. Tuna is a healthy source of protein and nutrients like omega-3 fatty acids, but it also contains mercury, which can build up in your body over time if you eat too much. The Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) recommend limiting tuna intake to no more than 3-4 servings per week for adults, to avoid potential mercury toxicity. Eating more than this amount consistently over time could lead to mercury poisoning.
How much tuna is too much?
According to the FDA and EPA, the recommended limits for tuna consumption are:
- 6 ounces (170 grams) per week for children
- 12 ounces (340 grams) per week for women who are pregnant or may become pregnant
- 16 ounces (454 grams) per week for other adults
One serving or ounce is about the size of a deck of playing cards. So for a 160 pound adult, 4 servings per week would be considered the maximum safe amount. Eating tuna every day or multiple times a day could put you over the recommended limit.
What are the symptoms of mercury poisoning?
If you eat too much tuna over a long period of time, mercury can accumulate in the body and cause toxic effects. Symptoms of mercury poisoning may include:
- Impaired cognitive function
- Memory loss
- Irritability
- Depression
- Headaches
- Nausea
- Vomiting
- Changes in vision or hearing
- Sensory disturbances like tingling
- Lack of coordination
The neurological symptoms are a result of mercury binding to nerve cells in the brain and spinal cord. Other organs like the kidneys can also be affected. If mercury poisoning goes untreated, it can lead to long-term health issues.
What factors determine mercury levels in tuna?
Several factors influence the mercury concentrations in tuna:
- Type of tuna – Mercury levels are higher in large predators like albacore and bigeye tuna, compared to skipjack and yellowfin.
- Tuna size and age – Older, larger tuna accumulate more mercury over their lifespan.
- Where tuna is caught – Some ocean regions have higher mercury levels.
- Fresh vs canned – Canned tuna tends to have lower mercury than fresh tuna steak.
For these reasons, light canned tuna generally has lower mercury content compared to albacore canned tuna or fresh tuna sushi and steak.
How does mercury get into tuna?
Mercury enters the oceans in several ways:
- Natural sources like volcanoes, forest fires, and breakdown of minerals
- Burning of fossil fuels like coal and release of industrial waste
- Historic mining activities that used mercury
Once in water, mercury makes its way up the food chain. Small fish absorb mercury from eating plankton. Medium fish eat smaller fish, accumulating more mercury. Top predators like tuna consume many smaller fish over their lives, accumulating even higher mercury levels. This process is called bioaccumulation.
Can mercury in tuna impact health?
Yes, mercury is a neurotoxin that can damage the brain, heart, kidneys, lungs, and immune system if too much accumulates in the body. Developing fetuses and young children are especially vulnerable. Some research also links high mercury exposure to increased risk of cardiovascular disease in adults.
However, these effects require very high intakes over a long period. Eating moderate amounts of tuna as part of a balanced diet is still considered safe and healthy. The omega-3s in tuna provide protection against mercury toxicity. Just be sure to choose low mercury varieties and limit intake to no more than a few servings per week.
Who is most vulnerable to mercury in tuna?
The populations most vulnerable to mercury exposure from tuna include:
- Pregnant women – Mercury can cross the placenta and affect the developing nervous system.
- Young children – The brain continues developing until about age 21.
- People who regularly eat predatory fish – Including tuna, mackerel, shark, swordfish, etc.
- Coastal communities with high seafood consumption.
To minimize risk, women who are or may become pregnant should avoid four+ servings of tuna per week. Parents should also limit tuna intake in young children and vary their diet with other low mercury seafood.
How can you prevent mercury poisoning from tuna?
To enjoy tuna safely:
- Eat no more than 3-4 servings of tuna per week as part of a balanced diet.
- Choose light canned tuna over white albacore tuna, which has 3 times the mercury.
- When eating fresh tuna, limit intake of fatty tuna like bluefin and bigeye.
- Avoid tuna every day – space out consumption throughout the week.
- Balance tuna with lower mercury seafood like salmon, shrimp, tilapia.
- Buy tuna from reputable sellers and pay attention to advisories in your area.
Monitoring your intake and varying your protein sources can allow you to get the benefits of tuna without overexposure. Speak to your doctor if you have specific concerns about mercury in your diet.
Can you get mercury poisoning from eating canned tuna?
It’s very unlikely you would get mercury poisoning solely from eating canned tuna. Here’s why:
- Canned light tuna has much lower mercury levels than fresh tuna.
- A typical can contains around 3 ounces of tuna, which is one serving.
- Toxic effects require eating way above the recommended limits consistently.
Eating a can of tuna daily could put someone over the weekly limit over time. But spaced out as part of a varied diet, canned tuna is generally considered safe by health authorities. Pregnant women and parents of young children should take extra care to limit intake and choose low mercury seafood.
How long does mercury stay in your body after eating tuna?
The half-life of methylmercury, the form found in fish, is about 50 days in the human body. This means it takes around 50 days for half of the mercury to be eliminated from your system after eating contaminated fish.
Full excretion of mercury takes much longer, around 3-5 months. This is why mercury can accumulate over time if you eat contaminated seafood regularly. Once exposure stops, levels will gradually decline over several months as it clears from your tissues.
Some mercury may persist longer, especially in people with frequent tuna intake that exceeds guidelines. Hair or blood tests can help diagnose if you have excess mercury. Avoiding tuna and high mercury fish for months may be advised. Be patient, as it takes time for the body to excrete mercury after heavy exposure.
Can you remove mercury from tuna by cooking it?
No, cooking tuna does not remove or destroy the mercury – it simply remains in the flesh. Here are some key points:
- Mercury in tuna and fish is primarily in the form of methylmercury, which binds tightly to proteins in muscle tissue.
- Methylmercury is not degraded or volatilized at normal cooking temperatures.
- You cannot remove mercury by baking, broiling, microwaving or any other home cooking method.
- Canned tuna still contains the same mercury levels as fresh tuna.
For this reason, there is no way to make tuna completely mercury-free at home. Your best bet is to choose low mercury species like light canned tuna. Proper handling and cooking can minimize other contaminants, but has no effect on methylmercury levels already present in tuna.
Can you develop an allergy to tuna by eating it too much?
Yes, it’s possible to develop an allergy to tuna after frequently eating it by becoming sensitized to specific proteins. Here’s some information:
- Tuna allergies are one of the most common fish allergies, along with salmon and halibut.
- Symptoms may include rash, hives, itching, nausea, vomiting, diarrhea, abdominal pain.
- Reactions are caused by the immune system mistakenly targeting tuna proteins as foreign/harmful.
- Repeated exposure over time causes progressively stronger immune responses.
- Cooking or processing tuna does not eliminate the allergenic proteins.
- An allergy can develop at any age, even if you have eaten tuna safely before.
If you suspect you may be developing a tuna allergy, see an allergist. Stopping consumption and avoiding tuna for a period may be advised to see if symptoms resolve. Once a fish allergy develops, even small accidental exposures can trigger reactions. Carrying epinephrine may be recommended. Rotating between different protein sources can help prevent allergy.
Can eating tuna everyday increase mercury levels?
Yes, eating tuna daily can definitely increase mercury levels over time due to the cumulative effect. Here’s why:
- Tuna contains a form of mercury called methylmercury that is retained in the body for weeks or months.
- When intake exceeds elimination, mercury accumulates in tissues over time.
- Daily tuna portions add up to high weekly amounts above EPA/FDA guidelines.
- Higher consumption = higher mercury exposure as it bioaccumulates up the food chain.
- Light tuna has lower mercury content but it can still build up.
To be safe, adults should limit tuna to 2-3 servings per week, spaced apart. Pregnant women need to be even more cautious. Getting blood mercury levels tested can help assess if you need to reduce intake to allow your body to clear excess mercury. Avoid daily tuna until levels normalize.
Conclusion
In moderation, tuna can be part of a healthy diet. But consistently eating tuna every day, or in large amounts, can lead to mercury build up over months and years. This can impact the brain, heart, kidneys and nervous system if intakebecomes excessive. To enjoy tuna safely, pay attention to recommended guidelines for your age group, choose low mercury varieties like light canned tuna, and balance it with other seafood low in mercury. Monitoring consumption and getting medical advice if concerned can help minimize the risks. While tuna has great nutritional value, it’s best not to overdo it.
