The New Complete Book of Food
opaque. The loss of moisture also changes the texture of the shellfish; the longer they are
cooked, the more rubbery they will become. Shellfish should be cooked long enough to turn
the flesh opaque and destroy any microorganisms living on the food.How Other Kinds of Processing Affect This Food
Freezing. When you freeze shellfish, the water in their cells forms ice crystals that can tear
the cell membranes so the liquids inside leak out when the shellfish is defrosted—which is
the reason defrosted shellfish tastes tougher and has less B vitamins than fresh shellfish.
Defrosting the shellfish slowly in the refrigerator, lessens the loss of moisture and B vita-
mins. Frozen shrimp and prawns can be boiled whole, in the shells, without defrosting.
Canning. Virtually all canned shellfish is higher in sodium than fresh shellfish. To reduce
the sodium content, rinse the shellfish in cold water before you use it.Medical Uses and/or Benefits
As a source of calcium. Ground oyster shells, which are rich in calcium carbonate, are the
calcium source in many over-the-counter supplements. Calcium carbonate is an efficient
source of the mineral, but it is also likely to cause constipation.Protective effects of omega-3 fatty acids. Shellfish have small amounts of omega-3 fatty acids,
a family of fatty acids which includes the essential fatty acid linolenic acid. Two other
omega-3s, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), most abundant in
fish living in cold waters, are the primary unsaturated fatty acids in oils from fish (anchovy,
herring, mackerel, menhaden, salmon, sardines, trout, tuna) and shellfish, as well as human
breast milk.
The omega-3s appear to reduce the risk of heart attack and “sudden death.” A 20-year
project at the University of Leyden in the Netherlands, comparing the eating habits of more
than 800 men at risk of heart disease, found that men who ate more than an ounce of fish a
day had a 50 percent lower rate of heart attacks. Since then, a lengthening list of studies has
shown similar protection among men who eat fish at least two or three times a week. Pos-
sible explanations for this effect are the omega-3s ability to lower the levels of tryglycerides
in your blood (high triglycerides are a risk factor for heart disease) and the fact that your
body converts omega-3s to a compound similar to prostacyclin, a naturally occurring chemi-
cal that inhibits the formation of blood clots.
In the United States, about 250,000 people die each year from sudden cardiac failure
caused by ventricular fibrillation, an unexpectedly irregular heartbeat. Those most at risk are
people with blocked arteries (atherosclerosis), congestive heart failure, or abnormal thicken-
ing of the heart muscle. In a 1995 study from the Australian Commonwealth Scientific and
Industrial Research Organization (Adelaide), laboratory monkeys fed omega-3 oils from fish
had a steady heartbeat when exposed to electrical current twice as powerful as that which
caused ventricular fibrillation in animals that did not get the fish oils. However, the heart