DEAR DR. BLONZ: Please tell me what you know about activated charcoal as a dietary supplement. How much should one take, and how well does it work as a blood purifier? -- G.L., San Jose, Calif.

DEAR G.L.: Activated charcoal is a specially treated and purified form of charcoal. It is a very fine powder, giving it a very large surface area. Fine, powdered charcoal is an "adsorbent," which means it has an ability to attract and hold on to substances on its surface. (Contrast this with "absorbent," where liquids are soaked up as with a sponge.)

This adsorbency makes activated charcoal useful for water filters because it can grab and hold heavy metals, unwanted minerals and odor-causing particles. It is often the key ingredient in water pitcher filters designed to be changed every couple of months. In addition, activated charcoal may be recommended after an accidental ingestion of poison -- the adsorbent qualities hold on to the poison and prevent it from being absorbed through the intestines and reaching the bloodstream. According to a statement from the American Academy of Clinical Toxicology, activated charcoal is more likely to be beneficial if administered within one hour of poison ingestion.

It is unclear how activated charcoal could work as a blood purifier; it would be tough for it to purify the blood if it never gets absorbed into the body. Also, it's not be wise to consume activated charcoal on a regular basis, as it will also reduce the absorption of nutrients present in the stomach at the same time.

DEAR DR. BLONZ: I am concerned about the use of gums as food additives. Specifically, I am concerned about xanthan gum as used in salad dressings and chocolate syrup. Could regular daily use of chocolate syrup and salad dressing, over seven years, cause xanthan gum toxicity, or perhaps a gum buildup in the lungs or liver? -- J.T., Monroe, La.

DEAR J.T.: Vegetable gums such as agar, locust bean gum, tragacanth, xanthan gum and pectin are used as food additives to improve texture and spreadability, and to provide the slippery "mouth feel" normally associated with a butterlike product. These compounds are built like a carbohydrate, but they're not digestible so they don't contribute any calories to the item.

Xanthan gum is usually made from a specially fermented corn syrup. It was created at a USDA research station in Peoria, Ill., as part of a project to find new uses for surplus corn. Xanthan gum helps to thicken the texture of a food and it has proven itself to be quite versatile. Aside from syrups and salad dressings, it is found in pudding, sauces, baked goods and desserts. Because it is made from corn, xanthan gum should be avoided by individuals allergic to corn, but aside from that there do not appear to be any problems associated with its use. That means that when consumed as an additive in other foods, there is no evidence that it can build up or cause toxicity.

DEAR DR. BLONZ: Asian restaurants often list bean curd in their dishes. Is bean curd the same as tofu? Are they both made from soy products? I have searched forever for this information, and hope you can help. -- J.C., Chicago

DEAR J.C.: Bean curd is synonymous with tofu, both being soy products made with soybeans that have been soaked, crushed, cooked and filtered. Calcium sulfate is then added, causing the soy pulp to form a gel. The water is then removed as the soy is pressed into cakes.

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 happened to be talking to a co-worker this morning -- we are both cyclists and runners. He is over 50 and I turn 50 tomorrow. Someone gave him a banana and some oranges, and he re-gifted the banana to me, saying that is one food he has cut out of his diet since he turned the half-century mark. I had never heard that people over 50 should not eat bananas. Can you provide a list of foods that I should now consider eating more of, at my age? How about foods I should eat less? Also, does potassium intake become less important to the 50+ body, and if not, what other sources should I consider if I eat fewer bananas? -- R.M., Walnut Creek, Calif.

DEAR R.M.: It's great that you are active. Don't stop! I am not sure what is behind the rejected banana. Personally, I like to use a ripe banana in my morning granola. Is your co-worker on meds where potassium intake has to be carefully controlled? Potassium is an important mineral that can be thought of as hanging around inside cells. It tends to be plentiful in whole foods. Contrast this with sodium, which can be thought of as being outside cells in bodily fluids like blood. Sodium tends to be plentiful in processed foods, and, of course, in the salt shaker. Sodium can be more of a problem, especially if there are blood-pressure issues. Even if your co-worker has some misplaced concerns about the sweet taste of a ripe banana, it is ADDED sugar that is a health concern, not the naturally present sugars in whole foods.

You ask for a list of healthful foods, but there is no magic list for those over 50 that would not have worked earlier in life. I have always favored a Mediterranean-type diet, but eat from all cuisines. There has been some great research coming out reaffirming the healthfulness of this approach. For more on the Mediterranean diet, go to http://tinyurl.com/6ayebq. If there is one great tip to carry with you, it is to follow a meal that's a bit rich with one on the lean side. Have plenty of fruits, vegetables and grains. I also love dark chocolate for dessert, but that's me. You'll get a sense of balance, and with that as your "list," you can do (and eat) just about anything.

Keep track of your general food intake as best you can, because the basic metabolic rate begins to slow as we enter our middle years. It also makes sense to adjust your exercise/workout goals as the years pass, to avoid injuries as the body shifts to middle-age and beyond. A common sense indicator is to watch the numbers on the scale, and how your clothes fit. Some change is inevitable, so it's nothing to get frantic about. It is great that you are active as it helps with weight, metabolism, staving off cognitive decline, and even with stress control; healthful foods are your best insurance.

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 am highly concerned about part of your answer regarding lactose intolerance vs. allergy: "Lactose intolerance is not the same as a milk allergy, the allergy being where there is specific reaction to the protein in the milk or milk product. Cheese should be avoided by those with milk allergies. Butter does not contain protein, but in the unusual case of an acute allergic sensitivity, even this may have to be avoided."

I think you do a disservice to the food-allergic population by this statement. Any parent of a child diagnosed with a dairy allergy is told to avoid all dairy products -- butter included. We battle long and hard to educate family, friends and schools about food allergies and the risks our allergic kids face every day.

We know that it is the protein in foods that causes the allergic reaction in people. All foods contain some amount of protein; otherwise, people wouldn't be allergic to things like vanilla, garlic, watermelon and kiwi, to name a few -- things we do not think of as having protein. So while butter may not have a high protein content, it certainly contains trace amounts and is on the no-no list for anyone diagnosed with a dairy allergy.

I understand that you write your article for the general public, but we face enough skepticism as it is when we attempt to educate people about food allergies. Statements such as the one in your column only make things harder in that regard. -- C.O., via email

DEAR C.O.: You are right. I was mistaken and I apologize to you and others who may have gotten incorrect information. The Nutrition Facts label of butter does indeed show a "0" for protein, but there is a small amount present: about 0.12 grams of protein in a one-tablespoon serving. The Nutrition Facts label rounds to the closest whole number, so anything less than one half of one gram will show "0". Although it seems minor, this amount might be enough to cause a reaction in those with an allergy. My column was written to answer a question about lactose intolerance, but when I added a brief mention about milk allergies, I should have had butter on the "NO" list. This could have been followed with a qualification that some with a milder allergy may be able to tolerate small amounts, but it was incorrect to have it the way it appeared. Thanks for your note.

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.