DEAR DR. BLONZ: I purchased sugar-free ice cream and noticed that the carton stated "sugar alcohol: 7 grams per half cup." What is sugar alcohol, and is this anything I should be concerned about? -- D.D., Lafayette, Calif.

DEAR D.D.: Most think of alcohol in relation to beverages and the ethyl alcohol they contain, but in chemistry, the term "alcohol" can refer to any compound containing a particular chemical structure. A sugar alcohol belongs to the family of carbohydrates having the "alcohol" structure and also a sweet taste. The sugar alcohols include sorbitol, mannitol, maltitol and xylitol. Each has a slightly different take on "sweet," but one thing they share is that you don't need to show an ID to buy products containing them (unless, of course, they also contain ethyl alcohol).

When compared to regular sugars such as sucrose, glucose or fructose, sugar alcohols contain about half the calories, they are not as rapidly absorbed and they have an insignificant impact on blood sugar level. This makes them useful as a sugar substitute for diabetics and others looking to limit their sugar intake.

Sugar alcohols are metabolized differently than other carbohydrates; one beneficial aspect of this is that they do not feed the acid-producing bacteria that live in our mouths. As such, sugar alcohols do not contribute to tooth decay.

They are not considered "sugars" for food-labeling purposes, and don't have to be declared on the label, but they can be. The FDA allows food sweetened only with sugar alcohols to be labeled "sugar free." While they have their benefits, be careful not to overdo it. Part of the sugar alcohol is not efficiently absorbed, and passes through and ends up being fermented by flora that live in the lower part of the digestive system. This can contribute to abdominal gas and cramping, especially when consumed on an empty stomach.

DEAR DR. BLONZ: I would like to find out more about hearts of palm. I eat them in a salad quite frequently, and it just occurred to me that it was part of the palm and I don't want to be adding palm oil to my diet. I belong to an eating club, and we are all senior citizens interested in living a long life. We debated the benefits and potential dangers of this at our last meeting, and are all anxious to know your answer. -- G.G., Tucson, Ariz.

DEAR G.G.: Hearts of palm come from the palm plant, but not from the oil-containing portion. A one-third cup serving of hearts of palm contains less than a half-gram of fat, 14 calories, 207 mg of sodium, 1.5 mg of iron, and 1 gram of dietary fiber, together with manganese and smaller amounts of vitamin C, folate and other nutrients.

Finally, why do you classify palm oil as a no-no? This undeserved reputation originated from the misplaced branding of palm oil -- and all other tropical oils -- as foods to avoid at all cost. These foods, especially when present as a part of a whole food, can play a role in any well-balanced diet.

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 I am cooking chicken thighs or breast pieces and remove the skin and underlying globs of fat, would the dark meat still have more fat than the white? -- B.B., San Diego

DEAR B.B.: The fat in chicken tends to be stored under the skin, with some being deposited around the individual working muscle groups. The larger breast muscle is the leanest meat because it's a muscle that doesn't do much work, given that the chicken is a flightless bird. The leg muscles contain many different bundles of muscles, each requiring an efficient blood supply and available energy. The routine of the chicken is to stand around and eat most of the day, and this favors the laying down of body fat, some of which gets stashed in and around the muscles. (The same thing happens to us!) The thigh and leg areas contain a number of muscle groups responsible for support and movement of the chicken, and fat can be stored in and around these working muscles. This helps explain why dark meat tends to have slightly more fat than white meat.

An interesting aside: The "dark" of dark meat doesn't come from fat; it comes from myoglobin, an oxygen-carrying protein pigment that is present to a greater degree in working muscles. Chicken breast meat is light because it contains lesser amounts of myoglobin. Consistent with this theme, the breast meat of birds that fly, such as ducks or geese, is not "white meat."

DEAR DR. BLONZ: I keep hearing about broccoli as an anticancer food because it contains sulforaphane, and wanted some information about what this is. I usually prepare my broccoli by steaming it on the stove, but sometimes in the microwave. I make a simple sauce or use a bit of butter. My question has to do with overcooking and how this might affect broccoli's benefits. Also, what is the relative nutritional value in the paler stems compared to the darker tops? -- P.P., San Francisco

DEAR P.P.: Broccoli is a member of the crucifer family, which also includes cauliflower, Brussels sprouts, kale, bok choi, turnips, rutabagas and cabbage. The vegetables in this family contain a number of healthful phytochemicals. Broccoli, in particular, is high in vitamins A and C, and is also a source of vitamin K and dietary fiber. That paler fibrous stem you refer to contains less of those vitamins, but more fiber.

As you mention, broccoli does contains sulforaphane, a phytochemical associated with cancer-fighting properties. Young broccoli sprouts and seedlings are the richest source; the broccoli tops, called the florets, are the next best.

Of interest regarding cooking is the fact that there is an enzyme in broccoli that helps sulforaphane form, and this enzyme can be inactivated by excess heat. This means that uncooked or quickly cooked broccoli can offer more sulforaphane. This was confirmed by a study in the April 2007 issue of the British Journal of Nutrition. That study compared broccoli cooked in the microwave for 2 minutes (lightly cooked) with that cooked for 5.5 minutes (fully cooked). The study reported that the yield of sulforaphane was three times higher in the lightly cooked broccoli.

The take-home message is that broccoli and other crucifers are healthful foods. To maximize sulforaphane, you should keep cooking to a minimum. But please understand the most important bottom line: Food is to be enjoyed, so be sure to prepare your broccoli in the way that's most pleasing to your palate.

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: How long should milk be kept after the carton has been opened? -- S.T., Ripon, Wis.

DEAR S.T.: Milk and other dairy products usually have a sell-by date stamped on the container. Fluid milk is a perishable and it will spoil. The date on the container is the last day on which the carton should be sold. Manufacturers use these dates to tell retailers how long to sell the product, and the dates include an allowance for normal home use. That means that a gallon container will typically have an earlier sell-by date than a quart container that comes from the same batch of milk.

Assuming it has been opened prior to the sell-by date stamped on the container, a conservative estimate is that homogenized milk should keep for about five days. The point is that the clock begins ticking as soon as the carton is opened. There is some flex here: The fresher the milk and the more time it spends at a chilled temperature, the longer it will remain wholesome. Of course, a carton opened 10 days before its sell-by date will last longer than one opened on the sell-by date.

Please understand that the sell-by date is not a guarantee of freshness or safety. The breakdown of food is a gradual process and does not take place on one particular day. You always need to keep containers chilled and tightly closed. Never return unused milk back to the container. The accuracy of any dating system relies on the proper handling of foods. If there's been any mishandling by the manufacturer, trucker, supermarket or consumer, the life and safety of the product will be compromised.

In the end, consumers must trust their eyes, nose and palate in addition to the numbers stamped on a carton. If you notice an "off" taste, smell or appearance in any food, forget the date and toss it out.

DEAR DR. BLONZ: You will probably get a number of emails on this matter, but a plantain is a fruit, even if it is eaten as a vegetable. Even though seedless, it develops in the reproductive system of the plant. A vegetable is any other part of the plant, i.e., root, stem, flower. -- J.R.

DEAR J.R.: My apologies for the gaffe; thanks for pointing it out.

DEAR DR. BLONZ: I recently purchased a jar of peanut butter that was clearly marked "NO TRANS FAT per serving" However, in the "Ingredients" column, it listed partially hydrogenated vegetable oils (cottonseed, soybean and rapeseed). Is it possible that a food could contain partially hydrogenated vegetable oils but not trans fats? -- G.G., San Jose, Calif.

DEAR G.D.: Only a fraction of the fats undergoing partial hydrogenation will become trans fats; that percentage is determined by the starting material and the degree of hydrogenation desired. If there is no more than 0.5 grams of trans fat per serving, a product can be labeled as being "free" of trans fats.

I know that the advice is to zero out our trans fat intake, and this is something I support, but at the level of less than one half of one gram per day, there is no evidence that trans fats would have a measurable negative impact on health. It could become an issue if multiple servings were routinely consumed.

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.