Q. Are the salt substitutes sold in supermarkets more nutritious than regular table salt? What about taste?

A. Salt substitutes consist primarily of potassium chloride (table salt) in that potassium takes the place of sodium in the molecule. Although potassium is harmless for most people, individuals with kidney damage may have trouble getting rid of excess potassium, which can accumulate to toxic levels. Also, be aware that the taste of potassium chloride is distinctive and may take some getting used to. As an alternative to salt substitutes, you could consider making greater use of herbs and other seasonings that contain no sodium.

Q. Is honey more nutritious than sugar?

A. Unlike refined sugar, honey does contain small quantities of essential minerals (mainly potassium, calcium and phosphorus), but they're present in such minute amounts that they have little value for human nutrition. Honey and sugar have roughly the same number of calories per serving. The only major difference is that, whereas table sugar consists of pure sucrose, honey contains a mixture of fructose, glucose and smaller amounts ofother sugars.

Q. Because raisins, which are dehydrated grapes, are a good source of iron, dos that mean that grapes are also a good source of iron?

A. No. Because grapes have much more water than raisins, the nutrients are not as concentrated. In fact, ounce for ounce, raisins have almost 9 times the iron of grapes. 3 1/2 ounces of raisins provide close to 20% of the USRDA for iron

Q. Are oranges that have a greenish color ripe? Are they safe to eat?

A. Such oranges have undergone a natural process called "regreening", which happens when a ripe orange fruit pulls some of the green chlorophyll pigment from the leaves and stem of the tree back into the peel. Regreened oranges are actually riper than others and often sweeter. And they're perfectly safe to eat.

Q. Is barbecuing a safe way to cook meat?

A. The greatest hazard of barbecuing is that the cook will not use enough caution and get burned. Some people suggest that the barbecuing itself is dangerous, because the smoke, which is absorbed by the meat, contains benzopyrene, which, in its pure form, has been known to cause cancer in laboratory animals. However, in order to experience the same results, people would have to consume unrealistically large quantities of barbecued meat at a time.

Q. If the refrigerator door is accidentally left open a crack for several hours, will the food be harmed?

A. With the door open, your refrigerator runs constantly to keep its temperature setting. If it's set at 40¢XF or lower and running properly, your perishable food is probably still cold enough to be safe. If food is cold to the touch, it should be fine. The items you have to be most careful to check are raw meats and casseroles, especially if they are stored at the front of the refrigerator near the door.

Q. Do sweets and fatty foods increase the possibility that a teenager will have acne? A. Scientists have found no evidence of a direct link between diet and adolescent acne. The notion originated with the premise that because adolescent acne is caused by an excess of oil in the skin, a diet that contained less fat would reduce this oil. But the oil in the skin is stimulated by the hormones, not by French fries. (The rare exception is when there is a clear-cut case of food allergy.) Acne occurs when follicles under the skin become clogged with oil. Bacteria under the skin feed on the oil and release toxins that spill out onto the skin's surface. The result: a pimple. Fortunately, treating pimples that crop up on the face, back or other skin surfaces has been made easier by the recent development of a wide array of effective medications. Some of these new drugs are vitamin A derivatives---that is, compounds that are similar in structure to vitamin A. However, vitamin A itself will not "cure" acne and, in fact, can cause damage to the liver if taken in doses consume from foods alone. Only the medications prescribed by a dermatologist will do the trick.

Q. Is there a vitamin that prevents gray hair?

A. Although it's true that a deficiency of the B vitamin pantothenic acid causes gray hair in some laboratory animals, humans will not be spared the ravages of time by loading up on supplements containing this nutrient.

Q. Is it true that occasional fasting will eliminate toxins from the body?

A. Ironically, although many fasters believe they are eliminating "toxic wastes", chemicals known as ketone bodies begin to accumulate in the blood stream if they stop eating for too long. Ketone bodies are quite toxic and place a severe burden on the kidneys.
For some people, fasting leads to a loss of protein from muscles and vital organs, as well as a depletion of the essential minerals calcium, phosphorus, sodium and potassium.