Canned tuna is preserved tuna with a shelf life that can last several years. You probably take your canned tuna for granted, but it's only really been around since the 1900s. Before that, if you wanted a tuna salad or sandwich, you needed to find yourself a fresh or salted fish. Because of its convenience, low cost and nutritional benefits, canned tuna can be an easy food to incorporate into takeaway lunches or other meals. However, there is such a thing as too much tuna. Canned tuna may contain heavy metals and other elements, which means that this is not a food you should be eating every day. Certain people may want to avoid it entirely.
Eating Canned Tuna
At the supermarket, you'll often find a wide variety of canned tuna available. These products come from different types of tuna, as well as different countries. Some of the most popular types of canned tuna include albacore, bigeye, bluefin, skipjack and yellowfin tuna.
It's still true, though, that canned tuna actually has lower levels of mercury compared to fresh tuna. This means that you can safely eat canned tuna more frequently than fresh. The amount of tuna that's recommended depends on the type of tuna you choose to consume.
Eating Too Much Tuna
Fish are well-known for being an important source of vitamins and minerals, especially omega-3 fatty acids. However, fish are also known for their mercury content, and among the many different types of tuna, mercury content varies. The types known for mercury content include ahi, albacore and bigeye.
If you're a tuna connoisseur, you know that ahi and bigeye tuna are frequently used raw, in sushi, while albacore is one of the primary types of tuna used in canned varieties. Albacore, otherwise known as canned white tuna, has about 0.32 parts per million of mercury. There's also a second type of canned tuna, though — canned light tuna made from skipjack tuna. Canned light tuna only has 0.12 parts per million of mercury.
Mercury isn't something you should consume too often; it can be a neurotoxin. For that reason, adults should eat limited amounts of tuna. With albacore tuna, women should eat three 6-ounce portions of tuna per month, while men can have three 8-ounce portions. Children must have less — between two 4.5-ounce portions and one 3-ounce portion per month, depending on age.
You can safely eat more canned light tuna than albacore. Adults and children over six can eat this type of tuna once a week without issue. If you eat more than the recommended amount, you could get mercury poisoning. High levels of mercury in tuna can have side effects.
Symptoms of mercury poisoning include loss of coordination, memory problems, numbness, pain, problems with vision, seizures and tremors. Mercury poisoning can also cause problems with the development of your baby if you're pregnant.
Mercury is the element in fish with the worst reputation, but other toxins come into play, often due to contaminated water — and they can affect our health, too. These contaminants include arsenic, cadmium and lead.
The good news is that these heavy metals rarely reach levels that should concern you, as long as you're eating the recommended amounts of tuna. The bad news is that these contaminants are found worldwide — from Brazil to Ghana to Iran. The bottom line is that, while tuna fish is healthy and delicious, there are no benefits to eating it every day. Excessive consumption of tuna, even canned tuna, is bad for your long-term health.
- MedlinePlus: Mercury Poisoning
- U.S. Food and Drug Administration: Eating Fish: What Pregnant Women and Parents Should Know
- Harvard T.H. Chan School of Public Health: Fish: Friend or Foe?
- Food Chemistry: Human exposure to mercury, lead and cadmium through consumption of canned mackerel, tuna, pilchard and sardine
- Analytica Chimica Acta: Determination of histamine in canned tuna by molecularly imprinted polymers-surface enhanced Raman spectroscopy
- Food Additives & Contaminants: Part B: Lead, cadmium, arsenic and mercury in canned tuna fish marketed in Tehran, Iran
- Food Additives & Contaminants: Part B, Surveillance: Cadmium, lead, tin, total mercury, and methylmercury in canned tuna commercialised in São Paulo, Brazil
- Environmental Defense Fund: Mercury Alert: Is canned tuna safe?
- NBC News: How Safe is What's in This Can?
- Seafood Health Facts: Canned Tuna
- Environmental Research: Benefits and risks associated with consumption of raw, cooked, and canned tuna (Thunnus spp.) based on the bioaccessibility of selenium and methylmercury