DEAR DR. BLONZ: In a package of catfish filets I purchased, I noticed a number of ingredients of concern, given that I need to limit my intake of sodium. These include sodium tripolyphosphate, sodium hexametaphosphate, acid pyrophosphate, citric acid and salt. Since when is salt put on frozen fish filets? All those sodium compounds sound like a no-no for a person who has high blood pressure, such as myself. I hate to toss them, but since reading the ingredients, I have lost my appetite for them. -- H.T., San Diego

DEAR H.T.: Chemical names can sound intimidating. A fresh (or fresh-frozen) fish wouldn't be using these additives, but the product wouldn't have much of a shelf life.

As for the ingredients on your list, the first four are there to help maintain the quality of the product during its shelf life. To put it simply, there are chemical reactions that take place during spoilage, and these compounds keep the elements involved in these reactions away from each other. They are referred to as "sequestrants" because they "sequester," or keep substances from mingling and reacting together, with the net effect of delaying the food going "bad." Although it may not be what you had intended on purchasing, there is no evidence that these compounds are harmful; having them is certainly preferable to consuming a product that has begun to spoil. There would only be minimal sodium supplied by these ingredients, as they are only there in very small amounts.

Salt is added for flavor, and the amount added would depend on the manufacturer. This being a package of a processed fish filets, there should be a Nutrition Facts panel on the label that will reveal the total amount of sodium per serving, regardless of source. Use that as your guide. In the future, be sure to read the label completely before you buy.

DEAR DR. BLONZ: I'm a constant reader of your column and appreciate your practical approach to nutrition questions. In an issue of Women's Health, I read that brown rice contains arsenic, and that when boiled, it leaches out but then is reabsorbed. They recommended cooking brown rice in a coffeemaker: pouring water into it and letting it run through. Secondly, a doctor on PBS claimed that tuna has toxins, so it should be avoided. I'm in the habit of having brown-rice sushi with salmon or tuna, plus avocado, at least a couple of times a week. Is that harmful? Am I consuming arsenic and/or toxins? -- K.L., via email

DEAR K.L.: I periodically enjoy tuna and certainly have not sworn off rice -- especially brown rice. Granted, arsenic has a rather intimidating persona, but there are issues relating to the type and level of consumption. Read a more detailed perspective on arsenic in rice at tinyurl.com/lboa7gv.

As regards tuna, much depends on where and how it is caught. Read the review at tinyurl.com/hwmtfrt. (Note: These two articles are from the Berkeley Wellness Letter from the University of California, Berkeley. I serve on the editorial board of this newsletter.)

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: Is it true that there are important enzymes in raw milk that are destroyed by pasteurization, and that these enzymes are needed to assimilate the calcium from milk? I heard this from a doctor on a taped presentation, and was wondering if whether it's correct. -- E.B., Chicago

DEAR E.B.: This smacks of a bogus spin on a partial truth. First, there are indeed enzymes in raw (unpasteurized) milk; some come from the cow, and others can come from bacteria. These enzymes will be destroyed, in part, by the pasteurization process. The question is whether these enzymes are essential for the assimilation, or absorption, of the milk's calcium.

The answer here is "no." Or, put another way: The enzymes have not been demonstrated, by any competent and reliable evidence, to be essential to the process of calcium absorption.

One cow enzyme is called plasmin, a protein-digesting enzyme that we produce as well. The human body uses its plasmin to help dissolve blood clots. In milk, the bovine plasmin degrades the milk protein. This can play a role in the ripening of cheese, or leads to clumping and the development of "off" flavors and odors in milk that has been around too long.

Pasteurization is not a sterilization process, but it involves the application of heat to destroy potentially harmful microorganisms that can cause spoilage or disease. It knocks out some, but not all, of the enzymes and bacteria that are present. Refrigeration also serves to slow bacterial growth and enzymatic action. All this helps to explain why milk goes bad if it is allowed to sit too long or is stored at the wrong temperature. Storage time can be extended with milk products processed with higher temperatures (ultra-pasteurized) and packaged in aseptic containers.

I'm uncertain why the doctor in your presentation believes that the enzymes in raw milk are needed for us to absorb calcium and other minerals. What you heard on that tape smacks of an unscientific milk attack. If you are interested in debunking it, go to the source -- if you can find it -- and demand proof for those statements. If you find any substance, please make sure to send it my way; I would be interested in the basis used to promote such stuff.

There are a number of individuals who really do not like milk, with some feeling that it is an unhealthful food. I disagree, but it is certainly up to the individual to decide for themselves. Not everyone wants to drink milk, and not everyone needs to. Our freedoms allow us to make our own food choices.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I have an allergy to crab and lobster, due to the iodine. Shrimp doesn't bother me at all, but my big question is whether scallops fall into the crab/lobster category or into the shrimp category. I have wanted to enjoy these tender morsels for a long time, but am cautious, due to my fears of a potential heart-stopping reaction. -- J.B. Seattle, Washington

DEAR J.B.: The typical shellfish allergy is not due to the presence of iodine. Some people may react to iodine, but usually only when there is inadvertent exposure to large amounts, such as with a disinfectant used in surgery or other medical procedures. Iodine is an essential mineral needed by the body to synthesize its thyroid hormone, which is involved with the regulation of our metabolism. This mineral is found in most seafood, but it is also present in foods made with iodized salt -- including most foods served in restaurants.

When there is insufficient iodine, the thyroid gland, which is located in the throat, becomes enlarged and the condition referred to as "goiter" results. Goiter used to be common in the Great Lakes regions of the United States, but the condition was virtually eliminated following the addition of iodine to table salt in 1924.

Shellfish allergies tend to relate to a sensitivity to the protein found in shellfish. The shellfish family includes clams, crabs, lobsters, oysters, shrimp and scallops. Specific food allergies are possible, but it is unusual that one would be able to tolerate shrimp when crab and lobster set them off. Because scallops are in the shellfish group, it would be best to refrain from any experimentation -- especially if there is a risk of a "heart-stopping" reaction. The prudent approach would be to consult with an M.D. allergist. He or she can determine if it would be appropriate to give you an allergy test where you'd be exposed to very dilute extracts of the fish in a controlled, safe setting. Stay well.

DEAR DR. BLONZ: I am seeing a holistic medical doctor who relies heavily on a technique called "muscle testing" to determine which nutritional supplements I should be taking. The supplements are placed under my tongue, and then, while I am on my back, he has me raise my right leg about 10 inches (while the pill is still under my tongue). If he can press my leg down, he recommends that supplement be taken. If he cannot force my leg back down on the table, he says I don't need the supplement. What is your opinion of this technique? -- C.B., Los Angeles

DEAR C.B.: This test is dubious, to say the least. I have never found any evidence to support the reliability of such a technique. If it were me, I would find another doctor.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.