Q. In answering a recent question, you described copper as a relatively nontoxic metal. But I remember reading about a condition called Wilson's disease, in which people are quite sensitive to copper. Can you tell me more about it? How common is it?

A. Wilson's disease, or hepatolenticular degeneration, is rare. An inherited metabolic disorder, it is characterized by abnormal transport and storage of copper. Excretion of copper in bile is decreased and the mineral accumulates at toxic levels in vital organs including the liver, kidney and the cornea of the eye, causing not only liver problems but neurological and psychological symptoms.

When the need to reduce copper stores was first recognized, restricting intake was crucial to the management of the condition. Not only was dietary copper sharply limited, but only distilled water could be used for cooking and drinking, and sulfurated potash was taken with meals to tie up copper in the gastrointestinal tract and prevent its absorption.

About 30 years ago, the introduction of penicillamine, a drug that binds copper, reducing tissue stores and reversing clinical symptoms, eliminated the need for these measures. Nowadays, experts who treat the condition suggest that it is still wise to limit the intake of such copper-rich foods as liver, chocolate, nuts, mushrooms and shellfish.

Q. I had always thought that cooking reduces fiber content, but recently I read that cooking can increase the fiber in some foods. Is that true?

A. Cooking can increase the fiber content of foods. The browning process, or so-called Maillard reaction, is a chemical reaction between a carbohydrate and an amino acid that results in changes in both color and texture, creating molecules that closely resemble lignin, one of the components of fiber naturally found in food. Thus toast and bread crusts have more of this fiber fraction than either untoasted bread or the center of the loaf.

Lignin, like cellulose and hemicellulose, helps move the contents more quickly along the intestines. Along with pectin and gums, it may help control cholesterol levels. While cooking can increase the amount of lignin in food, it can also result in the loss of some of the other fractions of fiber, both gums and pectins.

It is important to depend on a variety of sources to get plenty of fiber in your diet: whole-grain breads, especially the coarser varieties; brown rice, seeds, and legumes; as well as fruits and vegetables, both raw and lightly cooked varieties. To minimize fiber loss, it is best to avoid peeling whenever possible.

Q. Is it true that a new test is now available to detect trichinella larvae in raw pork?

A. Yes. It has been possible to test for trichinosis in pork for 100 years. In 1891, the United States began to inspect pork being exported, because European countries claimed they would not otherwise buy it. But Europeans then enacted other protective measures to keep our pork from flooding their markets, and in 1906 we discontinued the program. Not only was it extremely expensive, adding 64 cents to each pound of pork in 1894, but the methods then available, although credited with dramatically lowering the incidence of trichinosis in Europe, were not entirely effective.

The new test, which is expected to cost only pennies per pig, has proven completely accurate. Named ELISA, for enzyme-linked immunosorbent assay, it is based on an antigen-antibody reaction. Trichinella antigens coat plastic wells of a test plate and trap the antibodies, which are present only in the blood of infected pigs. The reaction does not occur with pigs that do not harbor the disease. The difficulty in developing the test was to isolate the antigens secreted from the Trichinella larvae, a problem finally solved by Dickson Despommier of the Columbia University School of Public Health. The test has stood up to a variety of evaluations. It's not known just how soon our pork supply may be labeled as trichinella-free. The U.S. Department of Agriculture is testing 12,000 serum samples from slaughterhouses to get an idea of the prevalence of trichinosis.

The development of a completely effective and economical test will allow us to sell pork to countries that currently refuse to buy it. It is estimated that if U.S. pork is certifiably free of trichinella, the export market will increase by one-third and the domestic market by 2 percent the first year, for a total return of nearly $450 million.

Also, it is hoped that the new test may be useful for diagnosing the presence of trichinella in human serum during the early stages of the disease, when it can be treated. No such test is currently available. This same system may prove helpful in testing for other infectious diseases of animals.

Q. Long before new studies indicated that fish might help protect against heart disease, many health experts were encouraging people to eat more of it. Are people eating more fish?

A. According to statistics provided by the USDA's Economic Research Service, on a percentage basis people are eating over 20 percent more than they did 20 years ago. The increase sounds dramatic until we examine the actual figures. Per-capita consumption of fish has risen less than two-thirds of an ounce per week, and remains just under four ounces, without allowances for waste. Moreover, averages tell us nothing about how many people still eat none at all.

It is interesting to note that while fish consumption increased by 2.1 pounds (from 10.7 pounds to 12.8 pounds) between 1963 and 1973, it rose only one-tenth of a pound more over the next 10 years, despite the fact that nutritionists and other health experts continued to support the use of more fish as part of a diet designed to limit both total fat and saturated fat.

Q. Since I moved to a new area, I have noticed that my tea always contains a lot of dark particles which settle out as it sits and the cup is lined with a dark brown residue. Why?

A. In all likelihood you have moved to a so-called "hard water" region, where the water supply is alkaline and contains the minerals calcium and magnesium. The reaction occurs as the tea cools and the tannins, which are colorless, combine with these minerals to form dark brown tannin complexes. As you may have noticed, adding lemon juice -- thereby making the solution more acidic -- will reverse the reaction, dissolving the particles and lightening the color.

Copyright 1985, Washington Post Writers Group