Nutrition Myths
Mercury in fish

SUMMARY

  • The mercury level of some fish is dangerously high.
  • Predatory fish, such as shark, swordfish, marlin, or king mackerel, contain more methylmercury in a small serving than the weekly maximum safe limit for most people.
  • The over-consumption of any fish or seafood has the potential of accumulating specific toxins and can lead to an imbalance of nutrients.
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Mercury levels in fish

There is no doubt that seafood and fish contribute many excellent health benefits and is considered one of the healthiest food groups.

In addition to a wide range of health benefits, their flesh also concentrated methylmercury.

The concentration levels of mercury in fish depend on various factors such as the species, size and age of the specific fish or seafood. It also varies depending on the pollution levels of the waters from which the fish is extracted.

The health benefits of fish and seafood outweigh the risk of mercury exposure if: (1)

  • The fish and seafood consumed has low levels of mercury
  • It is consumed within the weekly recommended limits

Statistics

In the U.S. population, the total fish and seafood consumption is (2):

The current safe daily limit for mercury intake has been established to be 0.1 micrograms per kg of body weight. The following table shows some examples of safe weekly limit of mercury per body weight:

Body Weight (kg)Limit of mercury (mcg/week)
5035
6042
7049
8056
9063
10070

The general recommendations for the maximum safe limit intake of mercury vary slightly from country to country since fish may be caught in different waters with different pollution levels.

How much fish should you eat per week?

In summary, the recommendations for an adult are 2-3 serves (1 serve = 150g) of fish per week. If you wish to eat more than that, you should make sure that you include low mercury level species. (3)

For a special group: pregnant, planning to be pregnant or breastfeeding women (1 serve = 150g) and small children (1 serve = 85g) the recommendations are:

  • 2-3 serves per week of low mercury small fish or
  • 1 serve per week of catfish, orange roughy (deep sea perch).
  • Avoid fish high in mercury such as tilefish, shark, swordfish, marlin, and king mackerel. (1, 4)
    Australian authorities allow some intake of these fish (1 serve per fortnight). However, considering the potential dangers, many health professionals advise to avoid them altogether. (5)

NOTE: Due to varied levels of mercury in fish and seafood and recent evidence of the health risks associated with low levels of mercury intake the current official recommendations may be undervalued. In addition to following these recommendations, it is important to keep track of the fish consumption using the more detailed list of mercury contents. (6)

Mercury levels in fish

The following table shows the concentration of mercury in different species of fish and seafood in studies conducted between 1990 and 2010: (7)

SpeciesMEAN (PPM)MAX (PPM)mcg in 3 oz serving
TILEFISH  (Gulf of Mexico)1.453.73123.25
SWORDFISH0.9953.2284.575
SHARK0.9794.5483.215
MACKEREL KING0.731.6762.05
TUNA (FRESH/FROZEN, BIGEYE)0.6891.81658.565
ORANGE ROUGHY0.5711.1248.535
MARLIN *0.4850.9241.225
MACKEREL SPANISH (Gulf of Mexico)0.4541.5638.59
GROUPER (ALL SPECIES)0.4481.20538.08
TUNA (FRESH/FROZEN, Species Unknown)0.4151.335.275
TUNA (FRESH/FROZEN, ALL)0.3911.81633.235
BLUEFISH0.3681.45231.28
SABLEFISH0.3611.05230.685
TUNA (FRESH/FROZEN, ALBACORE)0.3580.8230.43
TUNA (FRESH/FROZEN, YELLOWFIN)0.3541.47830.09
BASS CHILEAN0.3542.1830.09
TUNA (CANNED, ALBACORE)0.350.85329.75
CROAKER WHITE (Pacific)0.2870.4124.395
HALIBUT0.2411.5220.485
WEAKFISH (SEA TROUT)0.2350.74419.975
SCORPIONFISH0.2330.45619.805
MACKEREL SPANISH (S. Atlantic)0.1820.7315.47
MONKFISH0.1810.28915.385
LOBSTER (Species Unknown)0.1660.45114.11
SNAPPER0.1661.36614.11
BASS (SALTWATER, BLACK, STRIPED) [3]0.1520.9612.92
PERCH (Freshwater)0.150.32512.75
TUNA (FRESH/FROZEN, SKIPJACK)0.1440.2612.24
TILEFISH (Atlantic)0.1440.53312.24
SKATE0.1370.3611.645
BUFFALOFISH0.1370.4311.645
TUNA (CANNED, LIGHT)0.1280.88910.88
PERCH OCEAN *0.1210.57810.285
COD0.1110.9899.435
CARP0.110.2719.35
LOBSTER (NORTHERN / AMERICAN)0.1070.239.095
SHEEPSHEAD0.0930.177.905
LOBSTER (Spiny)0.0930.277.905
WHITEFISH0.0890.3177.565
MACKEREL CHUB (Pacific)0.0880.197.48
HERRING0.0840.567.14
JACKSMELT0.0810.56.885
HAKE0.0790.3786.715
TROUT (FRESHWATER)0.0710.6786.035
CROAKER ATLANTIC (Atlantic)0.0650.1935.525
CRAB [1]0.0650.615.525
BUTTERFISH0.0580.364.93
FLATFISH [2*]0.0560.2184.76
HADDOCK (Atlantic)0.0550.1974.675
WHITING0.0510.0964.335
MACKEREL ATLANTIC (N.Atlantic)0.050.164.25
MULLET0.050.274.25
SHAD AMERICAN0.0450.1863.825
CRAWFISH0.0330.0512.805
POLLOCK0.0310.782.635
CATFISH0.0250.3142.125
SQUID0.0230.071.955
SALMON (FRESH/FROZEN) *0.0220.191.87
ANCHOVIES0.0170.0491.445
SARDINE0.0130.0831.105
TILAPIA *0.0130.0841.105
OYSTER0.0120.251.02
CLAM *0.0090.0280.765
SHRIMP *0.0090.050.765
SALMON (CANNED) *0.0080.0860.68
SCALLOP0.0030.0330.255

Tips on limiting mercury intake

  • Eat fish and seafood with a low level of mercury and high level of omega-3 fatty acids such as sardines, mackerel, herrings, Atlantic salmon, canned salmon and “light tuna”.
  • Avoid fish with a very high mercury concentration such as shark (flake), marlin, swordfish, king mackerel and tile-fish. Although it is most likely that the fish you eat contains mercury levels as shown in the “average amount” column, you can never be sure. Some fish have shown to have much higher levels of mercury shown in the “maximum amount” column. (8)
  • Use the above table of mercury levels in various fish and seafood to make your choices and to keep track of what you eat.

NUTRITION FACTS VS NUTRITION MYTHS

You will find a summary of the most common nutrition myths and evidence-based nutrition facts here.

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