Tuna is a popular and nutritious fish that is commonly eaten canned. With its high protein content and omega-3 fatty acids, tuna can be a healthy part of your diet. However, some questions arise around the safety of eating multiple cans of tuna per week due to the potential for contaminants like mercury.
Can You Eat 4 Cans of Tuna Per Week?
The short answer is yes, you can eat 4 cans of tuna per week, but there are a few caveats. The FDA recommends limiting canned light tuna to 12 ounces (about 2 to 3 cans) per week and albacore tuna to 6 ounces (about 1 can) per week.
These recommendations are based on the methylmercury levels commonly found in canned tuna. Methylmercury is a form of mercury that builds up in certain types of fish. In high amounts, it can be toxic to our nervous system.
Tuna are larger, long-lived predatory fish that accumulate more mercury in their tissues. The FDA set the recommendations to balance getting enough omega-3s and protein from tuna, while limiting potential mercury exposure.
So with 4 cans per week, you may slightly exceed the recommended limits depending on the size of the cans and if you choose light or albacore. Consuming more than the recommendations is not automatically dangerous, but the risks would increase with regular excess consumption.
Mercury Risks
Methylmercury is considered a possible human carcinogen and can cause neurological disturbances in adults and impair neurological development in fetuses and young children. However, most people do not consume high enough amounts from fish to cause mercury poisoning.
At the FDA limits of 12 ounces light or 6 ounces albacore tuna per week, mercury exposure is considered negligible and safe. Even occasional higher intakes are unlikely to cause harm in healthy adults.
But regular long-term intakes over the limits could potentially lead to mercury building up in tissues to unsafe levels. Signs of mercury poisoning include sensory disturbances, lack of coordination, and vision or hearing impairments.
Tuna Varieties
Light tuna has lower mercury levels than white and albacore tuna on average. This is why the FDA limits are higher for light tuna. Here are some specifics on the common types of canned tuna:
– Albacore (white tuna): Albacore is a larger species that contains around 0.32 parts per million (ppm) methylmercury on average. The FDA limit of 6 ounces per week is about 170 grams.
– Light tuna: Light tuna is usually skipjack tuna, which is smaller and contains around 0.12 ppm methylmercury on average. The 12 ounce per week limit is about 340 grams.
– Yellowfin: Yellowfin is also a smaller tuna species with approximately 0.16 ppm mercury. Intake should align with the light tuna guidelines.
So albacore tuna has roughly 3 times as much mercury as light tuna. But all varieties are well below the 1 ppm mercury level that the FDA considers dangerous.
Tuna Sizes
In addition to the variety, the can size also determines how much tuna you’re getting. Here are some common sizes:
– 2.5 ounces = 70g
– 5 ounces = 142g
– 6 ounces = 170g
– 12 ounces = 340g
A 12 ounce can of light tuna would take you to the FDA weekly limit in one can. Whereas with 2.5 ounce cans, you could have up to 5 light tuna cans per week before hitting the limit.
To stay under the recommendations, smaller cans or alternating light and albacore cans is best if eating tuna frequently. Or limit tuna to once or twice per week.
Benefits of Tuna
Now that we’ve covered the mercury risks, let’s discuss why tuna can also be a healthy fish to include in your diet. Here are some of the top health benefits:
High in Protein
Tuna is an excellent source of high quality protein. A 3 ounce serving of canned tuna can provide around 20 grams of protein. Tuna protein is complete, meaning it contains all of the essential amino acids we need to obtain through our diets.
Protein plays vital roles in building and repairing muscle tissue and supporting our immune systems. It also helps regulate blood sugar levels and keeps you feeling full between meals.
Low in Fat
In addition to being high in protein, tuna is relatively low in fat, especially when canned in water. A 3 ounce serving only has around 1 gram of fat from healthy unsaturated fatty acids.
Going for no oil added or canned in water varieties helps keep the fat content low. The omega-3 fats found in tuna provide anti-inflammatory benefits.
Rich in Vitamins and Minerals
Tuna is rich in a variety of vitamins and minerals that play essential roles in our health:
– Selenium: Tuna is an excellent source of the antioxidant mineral selenium, which supports immune function and thyroid health. Just 3 ounces provides over 100% of the RDI.
– Vitamin D: Important for bone health, vitamin D is found naturally in tuna. Many people are deficient in this vitamin.
– Vitamin B12: Tuna contains high levels of vitamin B12, which helps make DNA and form red blood cells.
– Niacin: Also called vitamin B3, niacin in tuna helps convert nutrients into energy and promotes healthy skin and nerves.
– Phosphorus: This mineral supports strong bones and teeth. Tuna provides phosphorus in addition to other bone-friendly nutrients like vitamin D, calcium and protein.
– Potassium: Important for controlling blood pressure, potassium is found in tuna and most meats and fish. Many people fall short in their potassium intake.
– Iron: Tuna contains some heme iron, the most bioavailable form that helps prevent iron deficiency anemia.
Heart Healthy Omega-3s
Omega-3 fatty acids are a stand out nutrient provided by tuna. They have strong anti-inflammatory properties and help reduce heart disease risk factors.
Research shows omega-3s can:
– Lower triglycerides
– Reduce blood pressure
– Improve arterial stiffness and blood vessel function
– Make blood platelets less sticky and prevent clotting
– Decrease inflammation
The American Heart Association recommends consuming fish high in omega-3s like tuna at least twice per week for optimal health. Pregnant women should aim for 8 to 12 ounces per week.
Nutrition Facts
| Nutrient | Amount in 3 oz (85g) |
|---|---|
| Calories | 93 |
| Protein | 20.7g |
| Carbohydrates | 0g |
| Fat | 1.3g |
| Saturated Fat | 0.4g |
| Monounsaturated Fat | 0.2g |
| Polyunsaturated Fat | 0.4g |
| Omega-3 Fatty Acids | 0.3g |
| Selenium | 57.1mcg (103% DV) |
| Vitamin D | 2.7mcg (14% DV) |
| Thiamin | 0.1mg (4% DV) |
| Riboflavin | 0.1mg (4% DV) |
| Niacin | 11.3mg (61% DV) |
| Vitamin B6 | 0.5mg (26% DV) |
| Folate | 2.6mcg (1% DV) |
| Vitamin B12 | 2.7mcg (113% DV) |
| Calcium | 15.5mg (2% DV) |
| Iron | 1.3mg (7% DV) |
| Magnesium | 41.4mg (10% DV) |
| Phosphorus | 252mg (25% DV) |
| Potassium | 363mg (10% DV) |
| Zinc | 0.6mg (5% DV) |
DV = Daily Value
As you can see, just one can of tuna can provide significant amounts of protein, omega-3s, selenium, niacin, vitamin B12, phosphorus and other vitamins and minerals.
Mercury Concentration by Species
In addition to the size, the specific tuna species impacts the mercury levels. Here is a comparison of the average mercury concentrations in common canned tuna varieties:
| Fish Species | Mean Mercury Concentration (ppm) |
|---|---|
| Yellowfin tuna | 0.16 |
| Skipjack tuna | 0.12 |
| Albacore tuna | 0.32 |
As shown, albacore tuna has the highest mercury levels, followed by yellowfin and skipjack. This table demonstrates why the FDA recommends limiting albacore intake compared to the other tuna species.
Canned Tuna and Pregnancy
Pregnant women need to be especially mindful of mercury exposure since it can impair neurological development in fetuses. The FDA provides these guidelines for pregnant women:
– Eat 8 to 12 ounces of lower mercury fish per week. This includes canned light tuna and other low mercury fish like salmon, shrimp, pollock, and catfish.
– Avoid high mercury fish like albacore tuna, swordfish, shark, tilefish, and king mackerel.
– Check advisories about the local fish caught from waters in your area.
– Limit white (albacore) tuna to 6 ounces per week.
Sticking to light canned tuna and other low mercury seafood during pregnancy can allow you to safely reap the benefits of omega-3s for fetal brain and eye development.
How to Reduce Mercury in Tuna
If you are concerned about mercury exposure from canned tuna, here are some tips to limit your intake:
– Choose skipjack or light tuna more often, and limit or avoid albacore.
– Look for small can sizes, like 2.5 or 5 ounces instead of 12 ounces.
– Consume tuna in moderation along with other low mercury fish like salmon, sardines, anchovies and herring.
– Avoid tuna everyday and limit intake to a couple times per week at most.
– Purchase brands that have lower tested mercury levels. Some brands screen for mercury.
– Remove darker meat portions which may contain more mercury.
– Avoid consuming the tuna broth or juices, which can concentrate mercury.
Tuna and Mercury Poisoning
While excessive tuna intake can potentially lead to dangerous mercury buildup over time, acute mercury poisoning from tuna is very rare.
Signs and symptoms of mercury poisoning include:
– Impaired peripheral vision
– Lack of coordination and balance
– Numbness in hands and feet
– Muscle weakness
– Irritability, anxiety, depression
– Impaired speech, hearing, memory and cognition
These symptoms typically arise after consuming extremely high doses of mercury over an extended time. Just occasionally exceeding the recommended tuna intake limits is unlikely to cause mercury poisoning on its own.
But if you regularly eat very large amounts of tuna over many years against advice, symptoms of mercury toxicity could potentially occur. Children are at greatest risk since their nervous systems are still developing.
Conclusion
Based on the FDA recommendations, you can safely consume up to 2 to 3 cans of light tuna and 1 can of albacore tuna per week. This allows you to gain the health benefits of tuna while minimizing mercury risks.
Consuming 4 cans total per week is unlikely to cause problems for most healthy adults. However, the mercury dose would exceed the strict guidelines.
Pregnant women, small children and those who eat tuna daily or in large quantities may wish to take extra precautions and consume less than the total recommended amounts.
Overall, tuna is a healthy and nutrient-dense fish that offers cardiovascular benefits. But intake should be moderated and balanced with lower mercury seafood. Monitoring the variety, can size and consumption frequency allows tuna to be safely enjoyed as part of a healthy diet.
