Health Benefits of Tuna

tuna-fish

An Important Message About Tuna

 

We have placed tuna on our “10 Most Controversial WHFoods List.” This list was created to let you know that even though some foods (like tuna) can make an outstanding contribution to your meal plan, they are definitely not for everyone. One of the most controversial aspects of tuna is its potential for contamination with mercury. In some areas of the U.S., up to 50% of tuna sold in markets may exceed the U.S. Environmental Protection Agency (EPA) 500 ppb safety level for human consumption. In addition to its potential for contamination with mercury, levels of preformed histamine in tuna make this fish more commonly associated with adverse reactions than other foods. Some species of tuna are also considered endangered. All of these issues contribute to the controversial nature of this WHFood. You can find more information about these issues by reading over our complete food profile for tuna.

Based on all of the research that we have reviewed, we do not think it makes sense for you to rely on tuna as a primary seafood source for key nutrients, including omega-3 fats, since all tuna species show some level of mercury contamination in research studies. However, we do think it makes sense for you to treat tuna as a fish that can be enjoyed multiple times per month, especially if you select tuna types with lower mercury risk. As a general rule, we would include both skipjack and tongol tuna in this lower mercury risk category, and in some cases yellowfin, although this species can have widely ranging mercury level due to its widely ranging size and lifestyle. For more details about our 10 Most Controversial WHFoods, click here.

What’s New and Beneficial About Tuna

 

  • Researchers have recently discovered that tuna contains the mineral selenium in an unusual form called selenoneine. This form of selenium plays an important role in the health of the fish by serving as an antioxidant and protecting the fish’s red blood cells from free radical damage. Interestingly, it is also able to bind together with mercury compounds in the fish’s body (including methyl mercury, or MeHg) and lower their risk of mercury-related problems. Because there are approximately 2-3 milligrams of selenoneine in a 4-ounce serving of tuna, we are likely to get some of this same antioxidant protection when we eat tuna. Equally interesting, perhaps tuna will turn out to be a fish that – even when contaminated with mercury – might pose less of a mercury risk than might otherwise be expected due to the presence of selenoneine. Further research is needed to determine if this decreased risk actually takes place, but we greatly look forward to the results of future studies in this area.
  • In a much-discussed recent study about fish intake and cardiovascular disease, researchers have uncovered a very interesting trend involving tuna. Over 15,000 U.S. men and women participated in this 15+ year study, and their intake of fish – including canned tuna, darker oily fish like salmon and mackerel, lighter non-oily fish like cod, and shellfish like shrimp and lobster – was compared with their likelihood of experiencing a specific type of cardiovascular problem called atrial fibrillation (AF). In AF, electrical impulses within the heart become irregular. In the broadest dietary context, total consumption of fish did not help these participants lower their risk of AF—even if fish were eaten more than twice per week. However, researchers did find risk of AF to be reduced when a specific combination of fish—namely, canned tuna and oily fish like salmon—was eaten more than twice per week. Interestingly, this specific fish combination was more closely related to decreased risk of AF than the total amount of omega-3 fatty acids provided by the fish. While we cannot be sure about the reasons for benefits from this specific combination of fish, the contribution of tuna to decreased risk of this cardiovascular-related problem seems important and worth careful future investigation.
  • During the preparation of tuna for canning, whole fish are often steamed for a period of hours, and during this process, a watery liquid (called cooking juice) is created that frequently gets discarded as waste by tuna manufacturers. In recent studies, however, scientists have examined the nutrient composition of this cooking juice and determined that small protein fragments—called peptides—are present in the cooking juice and that they possess strong antioxidant properties. The antioxidant properties of these tuna peptides include the ability to protect cell membranes from oxygen-related damage (a process called lipid peroxidation). While the manufacturing of canned tuna is obviously a very different and much more lengthy process than the very short duration cooking methods that you would be using to steam, sear, or broil tuna in your own kitchen, it is still very likely that your at-home cooking methods for preparing fresh tuna will result in creation of some of these same beneficial antioxidant peptides.

 

Nutrients in
Tuna
4.00 oz-wt (113.40 grams)
Nutrient%Daily Value

 

 tryptophan118.7%

 

 selenium75.8%

 

 protein67.9%

 

 vitamin B367.7%

 

 vitamin B659%

 

 vitamin B137.9%

 

 phosphorus27.7%

 

 potassium18.4%

 

 magnesium18.1%

 

 omega-3 fats13.7%

 

Calories (157)8%

This chart graphically details the %DV that a serving of Tuna provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Tuna can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Tuna, featuring information over 80 nutrients, can be found under the Food Rating System Chart.

  • Health Benefits
  • Description
  • History
  • How to Select and Store
  • Tips for Preparing and Cooking
  • How to Enjoy
  • Individual Concerns
  • Nutritional Profile
  • References

 

Health Benefits

 

Anti-Inflammatory and Antioxidant Benefits

 

No single category of nutrient has been more clearly determined to have anti-inflammatory health benefits than omega-3 fatty acids, and tuna is equally well-established as an important food source of omega-3s. In an average 5-ounce can of tuna, you are likely to get about 7-28 milligrams of EPA (eicosapentaenoic acid) and 140-850 milligrams of DHA (docosahexaenoic acid). Both EPA and DHA are critical omega-3 fatty acids for proper regulation of the body’s inflammatory system and prevention of excessive inflammation. Generally speaking, you’re likely to get more omega-3s from canned albacore than from canned “light” tuna made from other species of tuna like skipjack (but also at times including yellowfin, tongol, or bigeye). But you are also likely to get more mercury from canned albacore as well because albacore are typically larger and older, having had more opportunity to accumulate mercury from contaminated ocean waters.

Researchers in the Department of Marine Science at Coastal Carolina University in Conway, South Carolina have recently taken a very interesting approach to this controversial trade-off between the beneficial, anti-inflammatory omega-3s found in fish and their undesirable contamination with mercury. These researchers reviewed nutritional studies on the anti-inflammatory benefits of omega-3s to arrive at a daily intake recommendation of 500 milligrams for EPA-plus-DHA (combined). Next, they estimated how many servings of fish would be required to meet this recommended level. In the case of canned albacore tuna, for example, they estimated that a person would need to consume 9 servings per month (with 7 ounces per serving) to provide an average daily amount of 500 milligrams of EPA-plus-DHA.

Using a similar type of logic, they then took the National Academy of Sciences (NAS) recommended safe dose level for mercury, calculated a safe daily intake level of mercury from fish of 6.8 micrograms and estimated how many daily fish servings a person could consume without going over this 6.8 microgram limit. In the case of canned albacore tuna, they determined that only 3 servings of canned albacore tuna could be eaten each month if a person wanted to stay below the 6.8 microgram daily limit for mercury. Based on this logic, they concluded that canned albacore tuna did not provide a good trade-off between omega-3s and mercury since a person would need 9 servings per month to meet the omega-3 recommendation, but would actually have to stop after 3 servings in order to stay below the mercury limit. In fact, these researchers did not find any type of tuna (not only canned albacore, but also canned light tuna and wild ahi tuna) that was able to meet the omega-3 recommendation without exceeding the mercury limit. They did find other fish, however, that provided the desired amount of omega-3s without going over the mercury limit. These other fish included salmon, trout, shrimp and tilapia.

While we admire the creativity and logic used by these researchers to evaluate the trade-off between omega-3s and mercury in fish, we take a somewhat different approach while using their same logic. Like these marine science researchers, we think it’s important for individuals to minimize their food exposure to mercury, and we like the idea of staying below the NSA limit. However, we also believe there is no reason for a person to depend exclusively on fish for their omega-3s, nor do we believe that all of a person’s omega-3s must be provided in the form of EPA and DHA.

Many foods can provide small amounts of omega-3s, and other forms of omega-3s (like alpha-linolenic acid, found in many plant foods) also help to provide us with anti-inflammatory benefits. For these reasons, we believe that individuals have the flexibility to enjoy tuna and other types of fish by focusing on their overall diet and making sure they get plenty of anti-inflammatory omega-3s from all of their foods combined, while still staying below the mercury limit in their overall diet. From a practical standpoint, this approach means including a variety of omega-3 foods in the overall diet, emphasizing fish that are lower in mercury contamination, and including higher mercury fish on a more limited basis. Wild-caught Alaskan salmon, for example, could be eaten during the same week as tuna to help avoid excessive mercury exposure while still reaping the anti-inflammatory benefits of omega-3s.

While small amounts of antioxidant nutrients like vitamin C, manganese, and zinc are provided by tuna, it is unusually rich in one particular antioxidant mineral, namely, selenium. This antioxidant is not only concentrated in tuna but is also present in an unusual form called selenoneine. Selenoneine is especially helpful to the tuna as a nutrient for protecting their red blood cells from free radical damage. Interestingly, it is also able to bind together with mercury compounds in the fish’s body (including methylmercury, or MeHg) and lower their risk of mercury-related problems. Because there are approximately 2-3 milligrams of selenoneine in a 4-ounce serving of tuna, we are likely to get some of this same antioxidant protection whenever we eat tuna. Equally interesting, tuna may turn out to be a fish that – even when contaminated with mercury—might pose less of a mercury risk to humans than might otherwise be expected due to the presence of selenium in this special form of selenoneine.

When you steam or sear or broil fresh tuna at home, this cooking process may also result in some special antioxidant benefits. These benefits are related to the presence of small protein fragments—called peptides—that may get formed during the cooking process when proteins in the tuna get broken down. Recent studies have shown that some of the protein breakdown products in tuna have strong antioxidant properties, including the ability to protect cell membranes from oxygen-related damage (a process called lipid peroxidation).

Other Health Benefits

 

When researchers study the overall benefits of omega-3 containing fish in a regular diet plan, they almost always find cardiovascular benefits to emerge at the top of the health benefit list. Researchers know, for example, that consumption of omega-3 fish can increase the presence of omega-3s in the membranes of red blood cells as well as cells along the blood vessel linings. This increased level of omega-3s in the circulatory system is associated with better regulation of blood pressure and lower risk of blood vessel “clogging.” Approximately 2-3 servings of omega-3 fish per week over the course of 3-4 months has been shown to provide these cardiovascular benefits, and in some studies, tuna has specifically been shown to raise bloodstream levels of omega-3s as described above.

Health benefits from tuna may also exist in the area of cancer risk. Here the research is somewhat mixed, for several reasons. First, there is very little research specific to tuna. Most of the large-scale studies have looked at fish intake overall, or fatty versus nonfatty fish, rather than tuna per se. Second, not all researchers classify tuna in the same way. Some classify it as a fatty fish, yet other classify it as a white fish (and non-fatty). Part of the reason for this inconsistency involves widespread consumption of canned albacore tuna, which typically contains less than 3 grams of total fat per ounce. In the area of colon cancer, there is clear evidence that increased intake of omega-3 fats from fish as a group can lower risk of this cancer type. While this fish group has almost always contained tuna in large-scale research studies, we’re not aware of studies in which tuna has not been analyzed independently as a unique fish for helping lower colon cancer risk. In the areas of prostate cancer and renal cancer, there is also some evidence of decreased risk from consumption of fish containing omega-3s, although the findings seem to be more mixed for these cancer types, with some studies failing to show decreased risk.

It’s worth adding that despite the relative absence of evidence regarding specific intake of tuna and cancer risk, there is a large amount of research connecting decreased overall cancer risk with increased intake of omega-3 fatty acids in the overall diet.

From an overall nutritional standpoint, tuna is more diverse in its nutrient content than many people would suspect. It’s an excellent source of vitamin B3 (niacin), and a very good source of other B vitamins including B6 (pyridoxine) and B1 (thiamin). Tuna is also a good source of the minerals phosphorus, potassium, and magnesium. Of course, because of its muscle content, tuna is an excellent source of protein, providing two thirds of the Daily Value (DV) in one 4-ounce serving. As we’ve previously discussed, it’s also a very valuable source of the omega-3 fatty acids EPA and DHA as well as the antioxidant mineral selenium.

Description

 

The tuna family is a diverse family of fish. Some tuna are classified as “pelagic” fish that live relatively close the surface or in water columns that extend downward for several hundred meters at most. Others are classified as “midwater” fish that can be found at depths up to 600 meters. Tuna swim in most of the world’s oceans. For example, there are six major stocks of albacore tuna, in the North Atlantic, South Atlantic, Indian Ocean, Mediterranean Sea, north Pacific and south Pacific.

This family of fish ranges widely in size. Some tuna – like bullet tuna – average about 1 foot in length. Other tuna—like Atlantic Bluefin—average over 6 feet in length and have been known to reach a size of 15 feet. Most tuna migrate over many miles of water (for example, some regularly cross the Atlantic or Pacific Oceans, over a distance of many thousand miles). While some smaller species of tuna live no longer than 3-5 years, it is not unusual for larger species like bluefin to live upwards of 20 years. All tuna belong to the scientific family called Scombridae, which also includes mackerel and bonito.

Among the most commercially popular of all tuna species are the following:

Albacore (Thunnus alalunga)

Albacore are a moderately sized and moderately long-lived species of tuna, with a common length of 3-4 feet, common weight of 15-45 lbs., and an average lifespan of 9-12 years. Albacore tuna can be labeled as “white meat” tuna when canned and has become a popular canned variety in the U.S. From a sustainability perspective, the Monterey Bay Aquarium Seafood Watch ranks canned albacore tuna as a “Best Choice” when caught by pole-and-line or by trolling in the U.S. Pacific or Canadian Pacific Ocean. Other stocks of albacore tuna swim in the North Atlantic, South Atlantic, Indian Ocean, and Mediterranean Sea.

Bigeye (Thunnus obesus)

While smaller and shorter-lived than bluefin (on average), bigyeye are still considered a large and long-lived species of tuna, able to reach lengths of eight feet or more and often averaging five to six feet. Bigeye are sometimes sold under their Hawaiian name, “ahi.” Along with yellowfin and bluefin, some bigeye are also used in sushi and and sashimi and labeled referred to as “maguro.” The Monterey Bay Aquarium Seafood Watch ranks bigeye tuna as a “Best Choice” when caught by pole-and-line or by trolling in the U.S. Atlantic.

Blackfin (Thunnus atlanticus)

Blackfin tuna belong to the yellowfin subgroup of tuna but have not become a commercially important species, unlike their yellowfin counterparts. Blackfin are relatively small in size, averaging between 1-3 feet in length and often 10-20 lbs.

Bluefin (Thunnus maccoyii—Southern Bluefin; Thunnus orientalis—Pacific Bluefin; and Thunnus thynnus—Atlantic Bluefin)

Bluefin are the largest of the commercial tuna species and can reach weights exceeding 1,000 pounds and lengths of nearly 15 feet. It is also common for bluefin to have a lifespan of 20 years, and in some cases, nearly twice that long. Bluefin are a popular species of tuna in preparation of sushi and sashimi, where they are often referred to as “hon maguro.” You can also find bluefin tuna being referred to as “toro” (tuna belly) when served as sushi. Due to their larger size and longevity, bluefin also average higher mercury concentrations than most other species of tuna.

Bluefin are also some of the most endangered tuna species. The International Union for Conservation of Nature (IUCN) in Cambridge, UK lists Southern bluefin as “critically endangered” and Atlantic Bluefin as “endangered.” Largely due to these environmental concerns, the Monterey Bay Aquarium Seafood Watch has also recommended avoidance of all bluefin tuna.

Skipjack (Katsuwonus pelamis)

Skipjack is the species of tuna that you are most likely to find in a can of “light” tuna. They’re a relatively small species of tuna, often weighing between five to six pounds and averaging one to two feet in length. Skipjack are also shorter lived, with a lifespan of two to three years. This combination of lifestyle circumstances also tends to make skipjack a tuna species that is lower in mercury accumulation.

Skipjack is most often sold as canned light tuna and is the most common species found in tuna cans. It’s also sold fresh or frozen.

When prepared for sushi, skipjack tuna is sometimes referred to as “bonito” or “katsuo,” and skipjack tuna is often used similarly to yellowfin tuna in preparation of sashimi. Some segments of the sashimi market prefer skipjack and use it interchangeably with yellowfin tuna in grilled or fried preparations.

The Monterey Bay Aquarium Seafood Watch ranks skipjack tuna as a “Best Choice” when caught by pole-and-line or by trolling in any region of the world.

Tongol (Thunnus tonggol)

Tongol (also called longtail) has become a popular alternative species of tuna in the canned “light” tuna market. Unlike many of its fellow tuna, tongol are less migratory, seasonal, and found primarily in the Indian and Western Pacific oceans. Virtually all commercially available tongol come from the coastlines of Malaysia, Indonesia, Thailand, and Iran (where the Indian Ocean becomes the Arabian Sea). Tongol are relatively small in size, averaging approximately 10-12 pounds and ranging from 1-3 feet in length. The overall lifestyle and size of tongol also make them lower in mercury accumulation in the limited data that we have seen. Although most canned light tuna features skipjack as its primary species, it’s becoming more and more common to find “light” canned tuna that include tongol. The Monterey Bay Aquarium Seafood Watch does not rank tongol tuna as a “Best Choice.” Yet, it does consider it a “Good Alternative” to other tuna types when caught by any method in Malaysia or when caught by pole-and-line or by trolling in Indonesia, Iran, or Thailand.

Yellowfin (Thunnus albacares)

Yellowfin are moderate-to-large sized tuna, ranging widely in size from one to two feet to as large as five to six feet, and in some cases, even longer. Smaller yellowfin average 10-12 pounds in weight, but larger yellowfin will average much more, in the range of 40-60 pounds (and in some cases, even more). Yellowfin are relatively fast growing and have an average lifespan of four to eight years. Their variable size also makes them variable in mercury accumulation, but most of the data we have seen on yellowfin show their mercury concentrations to fall at the moderate level. From a sustainability perspective, Monterey Bay Aquarium Seafood Watch ranks yellowfin tuna as a “Best Choice” when caught by pole and line or trolling in the U.S. Atlantic or Pacific Oceans.

Other Species of Tuna

 

Other species of tuna include bullet tuna (Auxis rochei), dogtooth tuna (Gymnosarda unicolor), slender tuna (Allothunnus fallai), frigate tuna (Auxis thazard), and kawakawa (Euthynnus affinis).

History

 

The evolution of ocean fish shows the emergence of tuna to have occurred approximately 45 millions years ago—long before humans were around to go fishing for them! Tuna swim in all of the earth’s oceans (except for oceans at the North and South Poles), including all parts of the Atlantic, Pacific, and Indian Oceans, as well as the Mediterranean Sea. There is evidence of Phoenician trap fisheries for tuna as early as 2000 BC.

For most of human history, fishing for tuna has been a small-scale regional and seasonal practice. The unique migratory patterns of tuna made small coastal fisheries for tuna the rule rather than the exception. Beginning in the 1940’s and 1950’s, however, industrial fishing for tuna started to become more and more widespread, with greatly expanded tonnage and offshore distances.

Even more recently, seafood production has witnessed the expansion of tuna farming. The farming of finfish like tuna in an open sea environment typically relies on the use of net pens to contain the fish. For example, a recent journal study using Google Earth documented the existence of 248 net pens for tuna in the Mediterranean alone.

How to Select and Store

 

Tuna is sold in many different forms. It is available fresh as steaks, fillets, or pieces. Tuna is probably best known in its canned form.

Just as with any seafood, it is best to purchase fresh tuna from a store that has a good reputation for having a frequent supply of fresh fish. Get to know a fishmonger (the person who sells the fish) at the store, so you can have a trusted resource from whom you can purchase your fish with confidence.

Fresh whole tuna should be displayed buried in ice, while fillets and steaks should be placed on top of the ice. Try to avoid purchasing tuna that has dry or brown spots.

Smell is a good indicator of freshness. Since a slightly “off” smell cannot be detected through plastic, if you have the option, purchase displayed fish as opposed to pieces that are prepackaged. Once the fishmonger wraps and hands you the fish that you have selected, smell it through the paper wrapping and return it if it has a truly strong fishy odor.

Canned tuna is available either solid or in chunks, and is packaged in oil, broth or water. Although the tuna packed in oil is usually the moistest, it also has the highest fat content, and the oils in which it is packed are high in omega-6 fats. Since omega-6s and omega-3s compete for the same enzymes that activate them for use in the body, and most Americans already consume too many omega-6 fats in comparison to omega-3s, it is best to purchase tuna packed in water or broth. Oftentimes, canned tunas do not distinguish which specific species was used except to note that it is either light tuna (bluefin or yellowfin) or white tuna (usually albacore).

When storing all types of fresh seafood, including tuna, it is important to keep them cold since fish spoils quickly and is very sensitive to temperature. Therefore, after purchasing tuna or other fish refrigerate it as soon as possible. If the fish is going to accompany you during a day full of errands, keep a cooler in the car where you can place your tuna to make sure it stays cold and does not spoil.

The temperature of most refrigerators is slightly warmer than ideal for storing fish. To ensure maximum freshness and quality, it is important to use special storage methods to create the optimal temperature for holding the fish. One of the easiest ways to do this is to place fish, which has been well wrapped, in a baking dish filled with ice. The baking dish and fish should then be placed on the bottom shelf of the refrigerator, which is its coolest area. Replenish the ice one or two times per day.

The length of time that tuna can stay fresh stored this way depends upon how fresh it is, i.e. when it was caught. Fish that was caught the day before you purchased it can be stored for about four days, while fish that was caught the week before can only be stored for about one or two days.

You can extend the shelf life of tuna by freezing it. To do so, wrap it well in plastic and place it in the coldest part of the freezer where it will keep for about two to three weeks.

All of these selection and storage steps for tuna are especially important due to special risk of histamine formation in tuna. Adverse reactions to histamine in tuna are often referred to as “scombrotoxic poisoning” since tuna belong to Scombridae family of fish. Failure to keep fresh tuna well chilled at refrigerator temperatures prior to cooking can result in increased histamine content and greater risk of adverse reaction. So can improper handling of canned tuna, in which a can is opened and allowed to sit at room temperature after being opened yet not consumed for several hours. The possibility of unwanted histamine formation in tuna makes it especially important for you to use care in the selection and storage of this food.

Tips for Preparing and Cooking

 

Tips for Preparing Tuna

 

After you unwrap your fish, rinse it under cool running water, then pat dry before cooking.

How to Enjoy

 

A Few Quick Serving Ideas

 

  • Tuna is a featured ingredient in the classic French dish, Salad Nicoise, which pairs tuna fish with steamed green beans and potatoes.
  • The sky’s the limit when making tuna salad since so many different ingredients nicely complement tuna’s mild flavor. Some of our favorite tuna salad ingredients include olives, chili peppers, leeks, fennel and walnuts. Try using fresh lemon juice, olive oil, and a little mustard for a healthier way to make a tuna sandwich instead of mayonnaise.
  • Stovetop Sear a tuna steak and add it to a salad of mixed greens and vegetables.
  • For an Asian-inspired meal with a hot streak, lightly brush a tuna steak with wasabi and soy sauce, and Quick Broil.

 

For some of our favorite recipes, click Recipes.

Individual Concerns

 

The U.S. Food and Drug Administration (FDA) has advised pregnant women, women of childbearing age who might become pregnant, nursing mothers, and young children (approximately 12 and under) to limit their consumption of albacore tuna to one six-ounce serving per week due to potential mercury contamination. (In addition, the FDA has recommended that these same population groups avoid certain fish altogether, including shark, swordfish, king mackerel and tilefish. For these population groups, an additional six-ounce fish serving per week is regarded as safe by the FDA, provided that fish lower in mercury are consumed. The FDA identifies these fish as shrimp, canned light tuna, salmon, pollock, and catfish.

We do not disagree with the logic of the FDA recommendations. Yet, we would also point out that “canned light tuna” may include skipjack, tongol, and yellowfin species and that some yellowfin tuna can be quite high in mercury accumulation. So as a general rule, “canned light tuna” that specify skipjack or tongol may provide you with lower mercury exposure.

Based on all of the research that we have reviewed, we think it makes sense not only for pregnant women, women of childbearing age who might become pregnant, nursing mothers, and young children to limit their consumption of higher mercury fish, but for everyone who wants to include fish within their meal plan. Accordingly, we do not think it makes sense for you to rely on tuna as a primary seafood source for key nutrients, including omega-3 fats, since all tuna species show some level of mercury contamination in research studies. However, we do think it makes sense for you to treat tuna as a fish that can be enjoyed multiple times per month, especially if you select tuna types with lower mercury risk. As a general rule, we would include both skipjack and tongol tuna in this lower mercury risk category.

In some cases, we would also consider yellowfin to be in the lower mercury risk category, although this species can have widely ranging mercury level due to its widely ranging size and lifestyle. For many people who want to err on the conservative side, it might make sense to avoid yellowfin tuna altogether if you are unable to determine its status as higher or lower in mercury. Because mercury levels in oceans are continuously changing, and because they can vary so greatly from ocean to ocean and even at different water depths within an individual ocean, levels in fish—including tuna—can sometimes be difficult to predict or even determine. One resource you can to follow-up on these levels is mercury and fish information provided by the U.S. Food and Drug Administration (FDA) at this website.

If you are making a decision about tuna consumption and have actual mercury data available like the FDA data above, you can generally regard tuna with mercury levels of 100 ppb or less as being “lower” in mercury, and tuna with mercury levels of 500 ppb or more as being “higher” in mercury.

Tuna and Purines

 

Tuna contain naturally occurring substances called purines. Purines are commonly found in plants, animals, and humans. In some individuals who are susceptible to purine-related problems, excessive intake of these substances can cause health problems. Since purines can be broken down to form uric acid, excess accumulation of purines in the body can lead to excess accumulation of uric acid. The health condition called “gout” and the formation of kidney stones from uric acid are two examples of uric acid-related problems that can be related to excessive intake of purine-containing foods. For this reason, individuals with kidney problems or gout may want to limit or avoid intake of purine-containing foods such as tuna.

General Allergic Reactions to Fish

 

Although allergic reactions can occur to virtually any food, research studies on food allergy consistently report more problems with some foods than with others. It’s important to realize that the frequency of problems varies from country to country and can change significantly along with changes in the food supply or with other manufacturing practices. For example, in several part of the world, including Canada, Japan, and Israel, sesame seed allergy has risen to a level of major concern over the past 10 years.

In the United States, beginning in 2004 with the passage of the Food Allergen Labeling and Consumer Protection Act (FALCPA), food labels have been required to identify the presence of any major food allergens. Since 90% of food allergies in the U.S. have been associated with 8 food types as reported by the U.S. Centers for Disease Control, it is these 8 food types that are considered to be major food allergens in the U.S. and require identification on food labels. The 8 food types classified as major allergens are as follows: (1) wheat, (2) cow’s milk, (3) hen’s eggs, (4) fish, including tuna (5) crustacean shellfish (including shrimp, prawns, lobster and crab); (6) tree nuts (including cashews, almonds, walnuts, pecans, pistachios, Brazil nuts, hazelnuts and chestnuts); (7) peanuts; and (8) soy foods.

These foods do not need to be eaten in their pure, isolated form in order to trigger an adverse reaction. For example, yogurt made from cow’s milk is also a common allergenic food, even though the cow’s milk has been processed and fermented in order to make the yogurt. Ice cream made from cow’s milk would be an equally good example.

Food allergy symptoms may sometimes be immediate and specific, and can include skin rash, hives, itching, and eczema; swelling of the lips, tongue, or throat; tingling in the mouth; wheezing or nasal congestion; trouble breathing; and dizziness or lightheadedness. But food allergy symptoms may also be much more general and delayed, and can include fatigue, depression, chronic headache, chronic bowel problems (such as diarrhea or constipation), and insomnia. Because most food allergy symptoms can be caused by a variety of other health problems, it is good practice to seek the help of a healthcare provider when evaluating the role of food allergies in your health.

Specific Adverse Reactions to Histamine

 

In addition to the possibility of a general allergic reaction to tuna, it is also possible for some individuals to have a specific adverse reaction to the histamine content in this food. Histamine is an amino acid-like molecule that is a naturally occurring both in the human body and in food. Yet, some people have adverse reactions to histamine when it is contained in food in higher concentrations.

Protein-rich foods are one type of food more likely to contain higher amounts of preformed histamine, and tuna is definitely a protein-rich food. In addition, aged protein-rich foods like aged cheeses and cured meats are also likely to contain more histamine. The process of tuna canning and the relatively long shelf life of canned tuna products make these canned products more high risk in terms of histamine content in comparison to fresh fish. However, most of the histamine problems that we have seen with tuna involve improper handling of this food. For example, failure to keep fresh tuna well chilled at refrigerator temperatures prior to cooking can result in increased histamine content and greater risk of adverse reaction. Improper handling of canned tuna, in which a can is opened and allowed to sit at room temperature after being opened yet not consumed for several hours, can also lead to greater risk. Adverse reaction to histamine in tuna is typically referred to as “scombrotoxic poisoning” since tuna belong to the scientific family of fish called Scombridae. You’ll also hear histamine itself being referred to as “scombrotoxin.”

Nutritional Profile

 

Tuna is an excellent source of heart-healthy niacin, free radical-scavenging selenium, and muscle-building protein. Some of the selenium is found in the form of selenoneine, which may be especially valuable in terms of its antioxidant properties. Tuna is also a very good source of energy-producing vitamin B6 and thiamin. In addition, it is a good source of anti-inflammatory omega-3 fatty acids (including eicosapentaenoic acid or EPA, and docosahexaenoic acid or DHA), bone-healthy phosphorus and magnesium, and heart-healthy potassium.

For an in-depth nutritional profile click here: Tuna.

In-Depth Nutritional Profile

In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Tuna is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.

Introduction to Food Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn’t contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food’s in-depth nutritional profile that includes values for dozens of nutrients – not just the ones rated as excellent, very good, or good – please use the link below the chart.) To read this chart accurately, you’ll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food’s nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration’s “Reference Values for Nutrition Labeling.” Read more background information and details of our rating system.

Tuna
4.00 oz-wt
113.40 grams
157.62 calories
Nutrient Amount DV
(%)
Nutrient
Density
World’s Healthiest
Foods Rating
tryptophan 0.38 g 118.8 13.6 excellent
selenium 53.07 mcg 75.8 8.7 excellent
protein 33.99 g 68.0 7.8 excellent
vitamin B3 13.54 mg 67.7 7.7 excellent
vitamin B6 1.18 mg 59.0 6.7 very good
vitamin B1 0.57 mg 38.0 4.3 very good
phosphorus 277.83 mg 27.8 3.2 good
potassium 645.24 mg 18.4 2.1 good
magnesium 72.57 mg 18.1 2.1 good
omega-3 fats 0.33 g 13.8 1.6 good

 

World’s Healthiest
Foods Rating
Rule
excellent DV>=75% OR
Density>=7.6 AND DV>=10%
very good DV>=50% OR
Density>=3.4 AND DV>=5%
good DV>=25% OR
Density>=1.5 AND DV>=2.5%
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