DEAR DR. BLONZ: I have a severe reaction to shellfish like crab and lobster, but eating shrimp doesn't bother me at all. My question relates to scallops: I want to be able to eat them, but am unsure if I can do so safely. The nutritionist I consult with said that my allergy was probably due to iodine, but I am not sure how this could be the case. -- S.I., San Jose, Calif.

DEAR S.I.: While some people may react to iodine, that is usually only when it's applied in large amounts as a disinfectant, as in surgery or other medical procedures. The typical shellfish allergy is not due to the presence of iodine. Iodine is an essential mineral needed by the body to make the thyroid hormone. It is found in most seafood, and is also present in foods made with iodized salt, which includes many restaurant foods.

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.

Rather than iodine, allergies to shellfish -- including clams, crabs, lobster, oysters, shrimp and scallops -- tend to be caused by a protein found in the shellfish. It is unusual that you would tolerate shrimp when crab and lobster set you off. Because scallops are in that shellfish group, I suggest you refrain from any experimentation -- especially because you classify your reaction as "severe." What you need to do is to speak with your physician -- not a nutritionist -- and undergo a standard allergy test conducted by an allergist. In these tests, you will be exposed to very diluted extracts of shellfish, along with other substances that may be suspect. The test is done in a safe, controlled setting.

DEAR DR. BLONZ: I have been advised to seek a holistic medical doctor who uses a technique called "muscle testing" to determine which nutritional supplements I should be taking. In this type of testing, the doctor places supplements under my tongue. Then, while I am on my back, he has me raise my right leg about 10 inches. If he can press my leg down, he recommends that the 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? -- B.R., Coolidge, Ariz.

DEAR B.R.: My opinion is that this test is questionable to say the least. I have never found any evidence to support the reliability of such a technique. I would approach with caution any other advice from the individual who told you to seek such stuff.

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: If blood glucose level is so important -- if it gets too low, we get weak or pass out -- why does the body automatically convert the carbohydrates we eat into fat? Why don't we store carbs like we do fat? -- R.S., Dublin, Calif.

DEAR R.S.: Plants are able to capture energy from the sun, photosynthesizing the sun's energy into carbohydrate using carbon dioxide from the atmosphere. The human body, like that of most other animals, can't do this. Our only source of energy comes from the foods we consume.

Fat gets used as the storage form because it is nature's most concentrated form of metabolic energy, containing over twice the energy per unit weight as proteins or carbohydrates such as glucose. A concentrated form of energy is essential for us because of mobility: If we stored the bulk of our energy as carbohydrate, we would be too bulky to move.

That provides a good contrast to plants, where the basic theme is staying put, sending roots into the soil for nutrients and growing leaves that are exposed to the sun. With sunshine comes more energy for growth, the production of flowers, and the eventual production of seeds for the next generation. Plants take in their "meal" of sunshine and convert their energy into carbohydrate because it takes up the most space per calorie, which then speeds their growth.

Although the "mission" of the plant is to grow rapidly while remaining in one spot, that of the seed is very different. A seed must be light enough to be carried by the wind or on the fur of animals, but after falling to the ground, it needs to have enough stored energy to fuel the process of sending out roots and growing shoots. Seeds' need for concentrated energy explains why they store their enery as fat, as opposed to carbohydrates like mature plants.

You asked about carbohydrate storage in our body. It turns out that there is a small amount in the form of glycogen, which is a branched chain of glucose molecules. Glycogen is stored in the liver and muscles. It gets used as a source of emergency muscle energy, or if the blood sugar level drops too low, but it's not a large amount: The average adult has just over 100 grams in the liver and about 250 grams in all the muscles combined.

DEAR DR. BLONZ: Why should you only take 500 milligrams of calcium at a time? My supplement contains 600 milligrams and I had been taking two at bedtime. I had heard that it is better to take them at bedtime, but now I hear differently. Could you please comment? -- S.A., Seattle

DEAR S.A.: The reason for the calcium limit is that the efficiency of absorption tends to decrease when a single dose exceeds 500 milligrams. Taking larger amounts means that more will end up passing through without being absorbed. It is probably wise to find a way to distribute your calcium in more than one dose, and taking it at mealtime is usually best.

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: My diet is questionable, and I was recently persuaded to start using the antioxidant Pycnogenol by some friends (and a bunch of online advertisements). I thought that this antioxidant might be the best for whatever ails you, but I was wondering what you thought. -- A.S., Puma, Ariz.

DEAR A.S.: I am not certain what you might have heard about Pycnogenol. It is indeed an antioxidant supplement, but I wouldn't say it is "the best" for anything that might ail you. In fact, I wouldn't say that of any one type of antioxidant or supplement.

The body relies on a number of antioxidants, many of which it manufactures from the raw materials present in your diet. Others come from the foods themselves, such as the naturally occurring antioxidant substances found in grains, fruits, greens and other vegetables. These are the precise substances those plants rely on as living organisms, and many are able to be absorbed and work for us, as well. The most important message here is that the key to good health, good nutrition and effective antioxidant protection is to have an entire team working together. Supplements might be able to pitch in if needed, but they cannot do it all. Think of the interactions between the nutrients and phytochemicals in various combinations of whole foods as being like music performed by a symphony orchestra. A "questionable diet" plus a "whatever ails you" supplement should never be thought of as a reasonable alternative.

DEAR DR. BLONZ: I have read of the many health benefits of drinking tea. Are the same benefits derived from iced tea? Also, does the decaffeination process change the beneficial characteristics of the tea? -- D.S., San Diego

DEAR D.S.: There should be no difference in the health benefits between a tea that is consumed iced and one that is taken hot. The decaffeination process, however, is a mixed bag. Some use a steam process, while others remove the caffeine through the use of solvents. One factor to consider is the potential loss of the tea's beneficial phytochemicals, and I would expect there to be a greater loss with the solvent extraction.

One study using animals reported that regular black tea was the most effective in preventing skin cancer, followed by green tea, decaffeinated black tea, and finally decaffeinated green tea. They all had beneficial effects; it was just a matter of degree. Of interest was the suggestion that the caffeine itself might have some anti-cancer properties. There have been studies that have found that adding caffeine back to the decaffeinated tea restored much of its anti-cancer abilities. Indeed, caffeine was even found to have an ability to prevent certain cancers on its own. Please understand that these are specialized research studies where relatively large amounts of tea extracts or solids are given for a short period of time. It is unclear how much we can generalize from these studies.

The bottom line is that tea is a beverage to be enjoyed however you like it.

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.