A. Mercury is a basic element of the earth that occurs naturally in air and water. It is also a by-product of industrial activity. In nature, mercury is emitted into the atmosphere through soil erosion, volcanoes, and forest fires. In seawater, the source is usually underwater volcanoes.
According to scientific estimates, the majority of the mercury released into the environment comes from natural sources.
A. methylmercury is an organic form of mercury produced in bodies of water through the action of bacteria. In small amounts, methylmercury is not harmful to humans but at very high exposure levels, it can be toxic. The key concern is that methylmercury may harm an unborn baby's or young child's developing nervous system if pregnant and nursing women consume large amounts of fish containing high levels of methylmercury.
To safeguard the public, the federal government has put in place very stringent restrictions, including issuing advice for pregnant and nursing women and women who may become pregnant about the best ways to add fish to their diets. This advice is very conservative and builds in a 10-fold safety factor - so that no one is at risk of exposure to the harmful effects of mercury.
A. Almost all ocean fish and seafood naturally contain minute amounts of methylmercury, due in part to underwater volcanic activity. But the amount in light canned tuna is exceedingly low. In fact, when the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) issued new advice about the best ways to limit methylmercury in the diet, FDA and EPA listed light canned tuna as one of the commonly eaten fish that contains very low levels of mercury.
Although canned albacore tuna contains somewhat more mercury than canned light tuna, the amount is still very low and well below government standards. That is why the new government advisory tells pregnant women that they can safely eat up to 6 ounces of albacore tuna in a week. In general, there are 2 ounces of canned albacore in a typical serving.
A. No. Studies find that the amount of mercury in canned tuna has not increased in the last 25 years. In fact, a Princeton University study, funded by EPA, compared mercury concentrations in Yellowfin tuna caught off the coast of Hawaii in 1998 with the amount of mercury in Yellowfin tuna caught in the same area in 1971. That study found no increase in mercury levels.
A. Canned tuna contains minute amounts of methylmercury. According to surveys conducted by FDA, canned light tuna has an average of 0.12 parts per million (ppm) and canned albacore tuna has an average of 0.35 ppm. To put these amounts into perspective, FDA has set a limit of 1.00 ppm for mercury in fish - and both canned light and albacore tuna are well below this level.
A. Nearly all fish contain trace amounts of methylmercury but in most cases, the levels are very low and not harmful to humans. However, FDA and EPA caution pregnant and nursing women, women who might become pregnant and young children not to eat shark, swordfish, king mackerel, or tilefish because these fish contain higher than recommended levels of methylmercury. To be on the safe side, FDA and EPA also recommend that these special groups should only eat one meal a week of fish from fresh water lakes and streams that has been caught by friends or family.
Q. Are Americans at risk for mercury poisoning from eating fish?
A. Nobody in this country has ever experienced mercury poisoning from eating fish. And the same is true for most countries around the world.
There have been four cases worldwide where people have been poisoned by consuming foods containing very high concentrations of methylmercury. During the 1950s, 111 people from Minamata City, Japan died or experienced neurological disorders from eating fish contaminated with very high concentrations of methylmercury - up to 40 parts per million, compared to FDA's limit of 1 ppm. In this case, an industrial facility was releasing manufactured methylmercury directly into Minamata Bay. A second incidence in 1965 occurred in Niigata, Japan where 120 people were similarly poisoned.
The other two incidents involved people in Iraq who ate bread from grain that was contaminated with a fungicide containing mercury. Here, the people were exposed to even higher levels of mercury than in Japan and thousands were hospitalized.
Q. Is anyone at risk from consuming too much mercury from canned tuna?
A. Absolutely not. Nobody eating canned tuna in the U.S. has ever consumed the amount of mercury that comes close to what scientists call the "no observed adverse effect level" - or the level linked to adverse health effects. This is also true in countries like Japan, where consumers eat significantly more tuna and other kinds of ocean fish.
A. Absolutely not. Activists who want to change environmental policy have cited this statistic as a way of scaring the public, and especially pregnant women. But this estimate is not based on any science. Instead, the activists have distorted a government study designed for another purpose to arrive at estimates that make good headlines but have no basis in fact.
Here is the real fact: every scientific study has found is that no one in the U.S. has levels of mercury in their system that would affect their health - by a wide margin. This is supported by two large studies conducted by the Centers for Disease Control and Prevention (CDC), which found all of the women and children studied were significantly below any known adverse effect level (confirming no one is at risk).
Q. Who regulates the levels of methylmercury in our food supply?
A. In the United States, the responsibility for regulating mercury is shared by the FDA and the EPA. Specifically, the FDA regulates fish and seafood that is sold in food stores and restaurants. The EPA regulates the amount of mercury released into the environment and works with state governments to develop fresh water fish advisories. In 2004, >FDA and EPA joined forces in issuing advice for pregnant women about the best ways to incorporate fish into their diet.
Q. What is the government's new advice regarding eating fish and who should be listening?
A. On March 19, 2004, FDA and EPA issued a joint advisory intended only for pregnant women and nursing women, women who might become pregnant and young children. The advisory states "women and young children in particular should include fish and shellfish in their diets due to the many nutritional benefits."
To help pregnant women and moms choose fish that are low in mercury, FDA and EPA have identified 5 commonly served fish with very low mercury levels: shrimp, salmon, pollock, catfish and canned light tuna. According to the government's advisory, pregnant and nursing women, women who might become pregnant and young children can safely eat up to 12 ounces of these fish each week.
The government advisory also tells these special groups that they can safely eat up to 6 ounces a week of canned albacore tuna. In general, there are 2 ounces of albacore in a typical serving.
However, the advisory also identifies those types of fish that have higher levels of methylmercury and should be avoided by pregnant and nursing women, women who might become pregnant and young children. These fish are shark, swordfish, tilefish and king mackerel.
Q. What is the basis for the government's new seafood consumption advice?
A. The FDA/EPA seafood advisory is based on a 10-fold safety factor, meaning that if pregnant and nursing women follow this advice, they will be consuming minute levels of mercury in fish that are at least ten times lower than the lowest level for any known risk. This level is the most conservative of any country in the world.
Q. Some organizations say that the government's advice doesn't go far enough. Who should I believe?
A. The government's advice is based on sound science and is the result of a painstaking process to protect the public health while still allowing pregnant and nursing women to benefit from the many health benefits of eating fish during pregnancy.
Q. As a pregnant or nursing woman, shouldn't I just play it safe and not eat fish during this period?
A. Instead of playing it safe, you would not be getting the important health benefits afforded by some essential omega-3 fatty acids found in fish, including canned tuna. For example, canned tuna contains DHA (docosahexaenoic acid), an omega-3 fatty acid that is essential for the healthy development of the fetus and young child. According to scientific studies, DHA comprises approximately 40 percent of the polyunsaturated fatty acid content in the cell membranes in the brain and 60 percent of the cell membranes in the retina and is transferred from mother to the fetus at a high rate during the last trimester of pregnancy.
It is because fish is so important to a pregnant and nursing woman's diet that FDA and EPA issued their new seafood advisory, which tells them how to receive the benefits of fish while reducing their exposure to mercury levels. According to the government advisory: "Fish and shellfish are an important part of a healthy diet... So, women and young children in particular should include fish or shellfish in their diets due to the many nutritional benefits."
A. Absolutely. Not only is canned tuna completely safe but it is also one of the healthiest foods that a growing child can eat. Tuna is an excellent source of protein and is easily digestible by young children. Canned tuna is also low in fat and calories, contains essential vitamins and minerals, and is rich in omega-3 fatty acids - which are especially important during early childhood for eye and brain development.
Besides all these health benefits, canned tuna is a "kid friendly" food that is tasty and adaptable to many different meal options. For these reasons, the FDA and EPA both encourage moms to serve fish, including canned tuna, to children on a weekly basis.
Q. I am not a pregnant or nursing woman. Do I still need to limit the amount of fish I eat?
A. The advisory issued by FDA and EPA is only intended for pregnant and nursing women, women who might become pregnant and young children.
For the rest of the U.S. population - such as men of any age and women who do not plan to become pregnant or are past childbearing age - the government and public health groups are advising people to eat more fish, not less. This is especially true for canned tuna, which is an excellent and affordable source of lean protein and certain essential vitamins and minerals. Canned tuna is also heart-healthy because it contains omega-3 fatty acids that help lower blood pressure and cholesterol. For these reasons, health experts, including the American Dietetic Association and the American Heart Association, recommend eating 2 to 3 servings of a variety of seafood weekly, including canned tuna.
Q. What about men? Should they be concerned about mercury in fish?
A. No. Most men would benefit from adding more fish to their diet. This is because fish, such as canned tuna, is high in protein, low in fat, and helps lower the risk of heart disease and other health problems.
Q. What are the benefits of eating canned tuna during pregnancy?
A. Besides being high in protein and low in fat, canned tuna contains two essential omega-3 fatty acids - DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) - that are especially important during pregnancy. According to numerous studies, DHA comprises approximately 40 percent of the polyunsaturated fatty acid content in the cell membranes in the brain and is transferred from mother to the fetus at a high rate during the last trimester of pregnancy. Along with DHA, the developing fetus uses EPA for the growth of the brain and the developing nervous system.
Of the top 10 most commonly consumed fish in this country, salmon and canned albacore tuna have the highest levels of the omega-3 fatty acid DHA - according to the U.S. Department of Agriculture (USDA) Nutritional Database.
Q. What are the other health benefits associated with eating canned tuna?
A. There is a growing body of research that links the omega-3 fatty acids found in canned tuna and other fatty fish with optimal brain function and cognition and improved eye and skin health. Moreover, studies show that these omega-3 fatty acids are protective against certain cancers and have a therapeutic effect on depression and specific autoimmune diseases including lupus, psoriasis and arthritis.
Canned tuna is also one of the best sources of selenium, which research suggests promotes sound health and may reduce cancer risk.
Q. What do health organizations say about the benefits of eating fish?
A. The American Heart Association (AHA) Dietary Guidelines includes a recommendation that people eat fish (including canned tuna) for heart health benefits. Specifically, the AHA says, "At least 2 servings of fish per week are recommended to confer cardio-protective effects." The guidelines also mention the beneficial effects of omega-3 fatty acids in fresh and canned tuna on other diseases such as inflammatory and autoimmune diseases.
At the same time, the American Dietetic Association (ADA) recommends eating 2-3 fish meals per week, and points to fish as a low-fat source of protein that may help lower cholesterol. In addition, the Association says that research shows a number of benefits from consuming omega-3 fatty acids, found mainly in fatty, cold water fish like tuna, salmon, sardines, mackerel and lake trout. According to the ADA, omega-3 fatty acids help make the blood less sticky, so it flows through blood vessels more easily and is less likely to form clots, which can contribute to heart attacks and strokes.
Additionally, the new Dietary Guidelines for Americans 2005 - issued in January 2005 by the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (DHHS) - encourages consumers to eat two eight-ounce servings each week of foods, such as canned tuna, that are rich in the omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).
Based on an extensive review of the science, the 2005 Dietary Guidelines Advisory Committee concluded that higher levels of the omega-3 fatty acids found in fish are associated with the reduced risk of both sudden death and death from coronary heart disease in adults. Specifically, the Dietary Guidelines Advisory Committee estimates a 30 percent reduction in the risk of coronary deaths with the increased intake of omega-3 fatty acids.
Q. What are the different types of canned tuna available for purchase?
A. Consumers can buy both light and albacore tuna in two forms: "solid" where a portion of the fish is cut to fit the can and packaged in one layer; and "chunk" where the can contains a mixture of cut pieces of varying sizes.
Q. How much canned tuna does the average American eat in a year?
A. According to the U.S. Department of Commerce, the per capita consumption of canned tuna in 2004 was 3.4 pounds. That is equivalent to 9 cans of tuna, on average.
A. In 2003, the U.S. Department of Commerce reported that the average person consumed 16.3 pounds of commercial fish and shellfish. Canned tuna represents about 20 percent of total consumption.
Revised: August 2005
