Fish Consumption to Promote Good Health and Minimize Contaminants – Translating the Evidence into Fish Consumption Guidelines

A key challenge for health care providers in formulating advice to patients about eating fish is to strike an appropriate balance between reducing risks from fish contaminants and preserving the overall health benefits of eating fish. Though little comprehensive testing of fish for contaminants occurs in the United States, guidelines based on currently available information should inform decision-making about what fish to eat, how much, and how often. In addition, because contaminant levels vary among bodies of water in different geographic areas, guidelines should be tailored to reflect state and regional advisories.²⁹

For most people. The majority of authorities, including ARHP and PSR, believe that the benefits of consuming seafood regularly, especially those types that are high in omega-3 fatty acids such as salmon, oysters, and rainbow trout, outweigh the risks of exposure to contaminants.^1,30,31 Various organizations recommend intakes of omega-3s between 200 and 1,000 mg a day—and a 3-ounce serving of canned salmon, for instance, contains 1,200 mg of omega-3s (both docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA]).³²

Two 3-ounce servings of fish a week are recommended, ideally from varieties that are high in DHA and EPA.^1,31 Two servings of fatty fish twice a week can supply 500 to 1,000 mg of omega-3s.³² If patients chose to eat more than two servings of fish a week, they should be advised to consume a variety of seafood types (assuming there are no advisories to restrict consumption of fish from local sources).^1,30 Species thought to be relatively low in contaminants and therefore safe to eat include cod, shrimp, canned chunk light tuna, and pollock.¹⁵ If patients choose to eat 6 ounces of albacore (white) tuna or tuna steaks, they should eat no other fish in the same week, since these fish may contain higher levels of mercury.^1,15 If they eat more than the suggested fish servings one week (because, for instance, they are on vacation in a locale where fish is a specialty), they should be advised to reduce their intake the next week.

Women of childbearing age who are or may become pregnant or who are breastfeeding. Like the general population, these patients benefit from consuming seafood, especially varieties that are high in omega-3 fatty acids.¹ In fact, a 2007 study of 8,000 British women published in The Lancet found that when women ate more than 12 ounces of seafood weekly during pregnancy, their children had higher verbal intelligence quotient (IQ) scores and better developmental skills than did children of women who ate no seafood or less than 12 ounces of seafood a week.³³ The investigators concluded that the “risks from the loss of nutrients were greater than the risks of harm from exposure to trace contaminants in 340 g [12 ounces of] seafood eaten weekly.”³³

The IOM says that it is safe for childbearing-age women to consume between 6 and 12 ounces per week of a variety of fish and seafood types.¹ To avoid mercury exposure, they should not eat swordfish, shark, king mackerel, or tilefish.¹ These large species eat other fish and can accumulate mercury over their long lifetimes at levels approaching or exceeding 1 ppm, the EPA maximum recommended level.^18,34 This level of contamination is sufficient to pose a risk to the developing brain of the fetus or infant, even with infrequent fish consumption.

A total of only 6 ounces of white (albacore) tuna or tuna steak should be consumed per week due to concerns about mercury, and women who eat these fish should eat no other types of fish that same week.¹⁵ Other fish varieties that contain “moderate” levels of mercury include bluefish, grouper, lobster, mackerel, marlin, and orange roughy. Women who are contemplating pregnancy at some point in the future should be counseled that avoiding consumption of mercury-containing fish for 6 to 12 months before becoming pregnant will lower the risk of fetal contamination from this particular food source to a negligible level.

Patients at risk for heart disease. Omega-3 fatty acids appear to be particularly beneficial for cardiovascular health.^30,35 A review study published in JAMA in 2006 indicated that consuming 1-2 servings a week of omega-3-rich fish reduces the risk of coronary death by 36% and total mortality by 17%.³⁵ The net benefit of eating fish may be compromised by toxic threats from PCBs and other lipophilic contaminants. A study of organic contaminants in salmon reported in Science in January 2004 concluded that, based on the presence of elevated PCB levels, no more than one meal of farmed salmon should be consumed per month.³⁶ Such reports set up competing concerns: losing the potential health benefits of omega-3 fats derived from fish or risking exposure to toxic pollutants. A strategy between these two extremes is reasonable and most health guidelines, including the American Heart Association recommendations, advise people at risk of heart disease to consume fatty fish twice a week.^1,30,31,35 If consumers at risk for heart disease choose to consume more than two servings of seafood per week, they should vary the types of seafood eaten to reduce their exposure risk to contaminants.

Children’s consumption. It is best for everyone to eat a wide variety of fish and seafood in order to decrease the risk of over-exposure to either mercury or PCBs and related toxicants. This is particularly true for small children, who often tend to eat a limited diet with strong preferences for certain foods. To reduce the risk of high exposure to pollutants from over-consumption of any one fish, parents should be advised to teach children from an early age to enjoy a variety of low-mercury, low-PCB fish and shellfish. Children up to 12 years of age can reasonably eat two 3 ounce servings of fish each week, and can eat up to 12 ounces of fish in a week without safety concerns, according to the IOM report.¹

Serving sizes should be smaller and proportional to body weight, for example, 1 to 2 ounces for a toddler and 2 to 3 ounces for older and larger children.

Shrimp and canned tuna are the most commonly eaten seafood and they tend to be popular with children. Recent surveys show that shrimp is unlikely to contain mercury but may contain some PCBs. Tuna does contain mercury, but levels in most cans of chunk light tuna tested by FDA in 2003 were low enough to be safe for children as part of a varied fish and shellfish diet. Fish sticks and fast-food fish sandwiches, also frequently eaten by children, are typically made from fish that are low in pollutants but are not recommended as good sources of omega-3s.^15,40