Mercury In Fish; Do We Absorb It?

I conducted a laboratory experiment in 1989 in which I planned to discover how much, if any, mercury stored in animal's bodies when they ate raw and cooked swordfish. I chose swordfish because it is considered to contain highest levels of mercury, and because it is my favorite-tasting fish. I wanted to know if I had been contaminating myself with that delicious tasting fish.

First, the lab technician placed ads for dogs and cats aged 11-14. We chose that elderly group because it is considered most susceptible to easy contamination and illness from all sorts of toxic sources, including food consumption. We obtained 8 dogs and 8 cats of various kinds. All appeared unhealthy.

To obtain a 30-60 pounds swordfish, I called several fishing boat businesses in Los Angeles and Ventura. After several days, I found 4 fishermen who promised to call me as soon as they, or one of their clients who was willing to sell his or her catch, caught a large-enough swordfish. After 5 days, I bought a 53 pound swordfish for the experiment. Seven cubes of swordfish equaling one pound were weighed, reduced[1], tested and analyzed for mercury content. The mercury level was very high at 13.3 µg/g (probably because of all of the military and industrial waste from Oxnard and Ventura).

I divided the dogs and cats equally into 2 groups: Group A ate raw swordfish and Group B ate the same swordfish baked on a stainless steel grid. I joined Group A, eating nothing but raw swordfish for 5 days. Each portion was weighed proportionately to the size and weight of the animal and recorded so that we would know how much mercury each animal consumed.

All animals were equipped with catheters to collect their urine. All urine and feces were collected, bottled in glass, labeled with the name/number of the animal and preserved in refrigeration without additives. Imediately after urinating, animals were allowed to exercise only on concrete because we did not want them eating any grass or dirt. Only 4-16 ounces of water were provided for each animal to drink, according to size and weight.

No food was consumed for the last 2 days of the 7- day swordfish-eating experiment. Group A (raw) showed excellent energy levels and calm dispositions throughout. Group B (cooked) showed fair to good energy levels with moments of erratic energy surges where they paced anxiously for up to 40 minutes.

After seven days passed, all urine and feces were weighed and tested in batches for each animal separately. Group B's (cooked) mercury-results ranged from 1.1-1.64 µg/g. Group A's (raw) mercury-results ranged from 12.25-13.03 µg/g.


Group B discarded in feces and urine only 8-12% of the mercury contained in the cooked swordfish that they ate. Group B retained 88-92% of the mercury contained in the cooked swordfish that they ate. (Some of the mercury may have exuded out of the skin, nails and hair).

Group A discarded in feces and urine 92-98% of the mercury contained in the raw swordfish that they ate. Group A retained only 2-8% of the mercury contained in the raw swordfish that they ate. (Some of the mercury may have exuded out of the skin, nails and hair).

When we examined the feces and urine from both groups under an electronic microscope, we saw that in Group B very few cholesterols (fats) attached to mercury molecules. In Group A, massive amounts of cholesterols attached and encapsulated mercury molecules.


Group B retained most of the mercury in the cooked swordfish and contaminated its consumers' bodies with mercury (neurological toxicity). Group A discarded most of the mercury in the raw swordfish, preventing mercury contamination within their bodies. Eating swordfish raw prevents mercury retention and contamination. Eating swordfish cooked causes mercury retention and contamination.


[1]: Both analytical methods were used for each animals waste:

EPA Method 3050B, and 7470A, respectively.