Be careful of the fresh tuna you buy and eat.
That’s the message from a medical study warning people who consume the popular fish.
The study, released today, says people who ate improperly handled tuna suffered histamine poisoning, with symptoms such as tightness in the chest and difficulty breathing, a rash, facial flushing, headaches and a metallic or peppery taste in the mouth.
The study, published in the current issue of the Journal of the American Medical Association, reports an increase in the number of cases of histamine poisoning, a condition requiring emergency treatment, after the consumption of tuna in North Carolina.
Bacteria Make the Toxin
Histamine poisoning occurs when patients eat fish in which bacteria have converted the amino acid histidine — found in the fish muscle — into histamine, a process that can be controlled by storing fish on ice.
It is generally not life-threatening, except it may be for certain people with heart conditions.
From 1994 to 1997, North Carolina had averaged two cases per year, but between July 1998 to February 1999, 22 cases of histamine poisoning had been reported to health officials, the researchers report.
Although the number of cases is small, the investigators believe more Americans may have been poisoned but don’t know it.
“The number of cases of histamine poisoning in the United States is underreported because doctors and people don’t know they are having it,” explains Karen Becker of the Centers of Disease Control and lead author of the paper.
Doctors may think a person is having a food allergy because the symptoms and treatment are similar, explains Becker. But someone does not have to be allergic to fish to get sick from histamine.
Tuna is a particularly troublesome fish for histamine poisoning, Becker says, because its body temperature is warmer than other fish and it therefore needs to be kept colder.
Tuna burgers also create problems because meat from the belly of the fish is often used to prepare them, Becker says. But the belly is near the tuna’s gut, where bacteria live, and if the meat is not kept sufficiently cold, the bacteria will grow and convert the histidine to histamine.
Cooking tuna does not eliminate the histamine. Canned tuna is not at risk because the tuna is treated properly, Becker says. Tuna used for sushi is usually safe, too, Becker says, because the handling is done with temperature awareness.
Don’t Panic, Just Become Tuna Conscious
“We don’t want to scare people,” says Becker. “We just want people to be more conscious about where they buy their fish and how the fish is prepared when they eat out.”
Becker recommends always buying tuna that is kept on ice, eating it soon after it is purchased and not letting it sit too long in the sun, say, as marinating tuna-kebobs before a barbecue.
Improper handling of the fish at four different restaurants throughout the state contributed to 21 of the 22 cases in the report. Eighteen had eaten tuna burgers.
Besides preparation problems, recreational fishermen may sell fish unscrupulously without treating it properly, says Nick Stolpe, spokesman for the Garden State Seafood Association.
The Food and Drug Administration and local health departments monitor the safety of fisheries and wholesalers. Restaurants must used licensed fish dealers.
Becker is calling for the development of a test to detect histamine in fish at docks and in restaurants so food safety inspectors and health officials can get a better understand the extent of the problem.