Fish and seafood are a wonderful source of lean protein, and can be an important and delicious part of our diet, unless, of course, you are vegetarian or vegan.  Who among us doesn’t like a nicely grilled piece of salmon,  San Francisco-style cioppino, or tandoori fish tikka from Indian cuisine?  Fish are also a wonderful source of vital omega-3 fatty acids, which are vital for proper functioning of so many important systems in the body.

You may be shocked to discover, however, that according to a recent study from the Biodiversity Research Institute in Maine, that 84% percent of all fish have unsafe levels of mercury, so it is really necessary to do your homework on this subject and become aware of which fish are the most contaminated, and which are more safe to consume on a regular basis.

The form of mercury that ends up in fish is called methylmercury, a particularly toxic form  of this element that is produced when mercury from industrial pollution ends up in our lakes, streams, rivers and oceans.   It then is transformed chemically into methylmercury by interacting with certain kinds of bacteria present in these waterways, and consumed by fish as they feed on the aquatic life around them.  Obviously, the bigger the fish and the longer its life, the more it consumes the smaller fish around it, and thus accumulates higher levels of methylmercury.

Below you will find a breakdown of some of the most common fish and seafood, based on how much mercury or other toxic contaminants they contain:

The eight most dangerous fish (avoid completely, if possible):

  • Mackerel (King)
  • Marlin
  • Orange Roughy
  • Shark
  • Swordfish
  • Tilefish
  • Tuna (Ahi or Bigeye)
  • Salmon (Farmed) — while lower in mercury, may contain dangerous levels of highly toxic PCBs


The following fish should be eaten 3x per month or less:

  • Bluefish
  • Grouper
  • Mackerel (Spanish, Gulf)
  • Chilean Sea Bass
  • Tuna (Canned Albacore, Yellowfin)


It is recommended that you consume no more than two cans per week of light tuna per week.  Chunk light tuna tends to contain less mercury than other varieties, so is the safest kind to eat.  Although sushi is a delicious treat for many people, it’s very important to watch out for the raw tuna and other species frequently used for sushi, as they tend to be high in mercury.

Some of the healthiest fish to eat:

  • Anchovies
  • Clams
  • Herring
  • Oysters
  • Perch
  • Sardines
  • Sole
  • Squid
  • Tilapia
  • Trout (freshwater)
  • Trout (Rainbow)
  • Salmon (not “farmed”)
  • Catfish
  • Cod
  • Crab
  • Flounder
  • Haddock
  • Scallops
  • Shrimp
  • Spiny Lobster


Special care must be taken by women who are pregnant (or are of childbearing age who may become pregnant), nursing mothers, and young children when it comes to avoiding high-mercury fish and seafood.  Mercury can be harmful to the developing nervous system of babies and children, both before and after birth, especially to cognitive, motor and sensory functioning, and readily passes from the mother to baby in utero, or through breast milk.

I urge everyone to become more educated about where their food comes from; in today’s toxic and polluted world, it’s necessary to really do some homework to find out what is in the food we eat, in order to make the healthiest possible food choices.  Mercury pollution is occurring on a global level, and no one country is an island of safety, as many parts of our food supply are imported from outside the U.S.

There is also the important issue of overfishing:  many species of fish and seafood are being severely overfished, many to such a degree that a danger of extinction arises.  On a moral and planetary level, we can choose to consume fish that are in abundance and thus not contribute to the environmental degradation that is rapidly occurring throughout the natural world.

I am not recommending that people avoid fish and seafood altogether, but it’s important to exercise caution when you are at the grocery store or at a restaurant, in order to make the safest possible selections.

For more information, please visit the following websites:


National Resources Defense Council:

Blue Ocean Institute:

Monterey Bay Aquarium:




Dr. Allen gives free lectures at the Library three to four times each year, on topics of interest from the cutting edge of integrative medicine.  If you would like to be added to our mailing list for these lectures and his other speaking engagements, please email