Q. While at the market buying molasses, I noticed several types. Can you explain the differences among them?

A. All molasses is the syrupy product left after most of the sucrose crystals have been removed from the concentrated juices of either sugar beets or sugar cane. By weight, nearly three-quarters of it is a combination of sugars, including sucrose, glucose and fructose. Most of the rest is water, with minerals accounting for a maximum of 5 percent of the total.

While we tend to think of molasses as a by-product of sugar production, some, the so-called "unsulfured molasses," is made directly from sun-ripened sugar cane. By contrast, the source of the sulphur remaining in some molasses is a compound used in producing sugar from beets. Blackstrap molasses, used mostly in rum production, is what's left after the concentration of sugar in the syrup is too low to be extracted. It often appears as an unpalatable ingredient in folk remedies.

Molasses provides some iron and calcium, as well as calories from sugar. Just how much will depend on the syrup's concentration. For example, light molasses contains less than 1 milligram of iron per tablespoon, while the blackstrap variety has three times as much, or over 15 percent of the Recommended Dietary Allowance. Similarly, the lighter type provides just a bit of calcium, but the darker syrup contains as much as you'd get from a half-cup of milk.

Q. Does sorbitol-sweetened candy cause diarrhea?

A. Yes. In fact, in large doses it has long been used as a cathartic. In a study reported several years ago, adults were given a dose of sorbitol equivalent to that in four or five sorbitol-sweetened mints. Over the next several hours, investigators ran tests to see whether the compound, a so-called "sugar alcohol," had been absorbed. They did this by measuring breath hydrogen. A rise in breath hydrogen would indicate that the compound had traveled, unabsorbed, to the colon where bacteria would ferment it. Information about a series of symptoms linked to poor absorption was also recorded. These included abdominal pain, bloating and diarrhea.

The tests showed that breath-hydrogen levels rose significantly in nearly 75 percent of the patients. Symptoms of varying severity, reported by half the subjects, began anywhere from 30 minutes to 3 1/2 hours after taking the sorbitol-sweetened drink.

Why are some people intolerant to sorbitol? Research has not yet found the answer. Unlike intolerance to sugars, such as lactose, the problem cannot be explained by an enzyme deficiency since it does not need to be broken down to be absorbed. One thought is that the difficulty occurs when the alcohol travels too rapidly to be absorbed. It's worth noting that sorbitol intolerance is sometimes mistaken for irritable bowel syndrome.

While sorbitol is best known as a sweetener in candies, it's naturally present in several fruits, among them cherries and some types of pears and plums. However, the concentration in fruits is far more dilute than that in mints. The amount in 3 1/2 ounces of cherries is similar to that found in a single sorbitol-sweetened mint.

Q. I run and would like to improve my endurance. At the health-food store, I saw a special supplement designed for athletes that contains vitamins, amino acids and essential fatty acids. Would it help me?

A. Not according to a study done a few years ago using a mixture similar to the one you describe. The supplement was given to a group of well-trained male volunteers paired on the basis of how far they ran each week.

One pair took three capsules a day of the supplement while the other was given three identical-looking placebos or "sugar pills." Neither subjects nor investigators knew who was receiving the preparation being evaluated.

Subjects performed two sets of exercise, once before taking the supplements and again after four weeks. In one, they exercised to exhaustion; in the other, they exercised for one hour at a predetermined speed requiring them to work at 65 to 70 percent of capacity.

The results? Tests showed that maximum oxygen uptake, a measure of endurance capability, did not rise at the study's end. Nor was there any change in the body's response to submaximal endurance exercise. Blood levels of free fatty acids, which spare glycogen and stave off fatigue, also failed to rise in those taking the supplement.

The upshot? There's no scientific evidence that a supplement of this type will improve your performance.

Q. I recall your column about making pie crust using polyunsaturated oil. That was before I dedicated myself to a heart-healthy diet. My husband and I aren't overweight and I like to make an occasional fruit pie. Could you print the recipe again for Joanie-come-latelies like myself?

A. With pleasure -- and with one caveat: Regardless of what type of fat is used, pie crust is high in fat and calories and should remain a sometime treat. To make a single crust, mix together 1 1/3 cups of flour, 1/2 teaspoon salt, 1/3 cup oil, and 3 tablespoons cold milk until it can be pressed into a ball. Besides containing unsaturated fat, this crust offers another advantage to busy cooks: Unlike most pie crusts, it need not be chilled. It can be rolled and baked as soon as it's mixed. An empty shell will bake in about 12 minutes in a 450-degree preheated oven.