Q: Is it safe to consume the internal organs of fish?
A: It may be risky, so you shouldn’t make it a regular habit. Eating fish offal—as the internal organs are collectively referred to—is becoming trendy among some adventurous eaters, as part of the “tip-to-tail” movement, where no part of the fish is wasted. And it has long been customary in France, Norway, Asia, and other parts of the world to eat the livers and heads, among other parts of fish, either as a delicacy or simply a cheaper source of nourishment.
But PCBs, dioxins, and other chemical pollutants concentrate in the organs (as well as in the skin and fat), with larger fish accumulating more. Fish brains and eyes, for example, are the primary targets for mercury accumulation, some papers have noted. Toxins from cyanobacteria (blue-green algae) can also accumulate in the organs of fresh-water fish, while ciguatera toxin has been found in large, warm-ocean fish, such as grouper, red snapper, and sea bass, especially in the internal organs. Cooking does not eliminate these contaminants.
The FDA, EPA, and many other health authorities thus advise removing the guts, kidneys, liver, and head (and trimming away the fat and skin) before you cook your fish. Pregnant women, in particular, should avoid these parts. An exception: Because they tend to have low levels of contaminants, tiny fish like whole sardines and anchovies are generally safe for everyone to eat in their entirety—but always heed local advisories about contamination.
What about that soft green “stuff” in lobsters? Called tomalley (or tamali), it functions as the liver and pancreas and so can also be a potential source of toxins. A few years ago, the FDA issued an advisory against eating the tomalley from Maine lobsters because it was found to have high levels of a toxin that causes potentially fatal paralytic shellfish poisoning. Health Canada (similar to our FDA) recommends that children not eat tomalley and that adults restrict their consumption. Similarly, experts often advise discarding the tomalley in cooked crab, often called mustard because of its yellowish-brown color.