Q: I recently ate lunch with a friend who claimed to be dieting. She chose the make-your-own salad bar while I had the daily special of broiled fish, green beans and parslied potatoes. From a glance at the composition of her salad, and the amount of dressing she poured over it, it seemed that she was consuming more calories than I was. Has anyone evaluated calorie consumption at salad bars?

A: Salad bars may provide an excellent nutrient-rich lunch but are not always low in calories. Reseachers at Mississippi State University reported the results of a small but cleverly designed study to compare the caloric content -- and the amount of carbohydrates, protein and fat -- in meals selected by women college students. They stood at the end of the cafeteria line and randomly collected trays from 12 students who had used the salad bar for their main course and 12 others who had chosen a hot meal. Students were allowed to replace the meal they had chosen free of charge.

Laboratory analyses of the meals the women had selected found no significant caloric difference between the two. Salad-bar meals averaged 1,000 calories, ranging from a low of 560 to a high of nearly 1,600. The meals in which a hot dish was the main course averaged 900 calories, ranging from 480 to about 1,250 calories.

One explanation of why hot meals were lower in calories was that condiments -- such as tartar sauce and ketchup, which might have been used on, say, the fried-fish entree -- were located beyond the tray collection point. They could have added an estimated 200 to 300 calories. And whether the students chose the hot meal or the salad bar, they also were allowed a specified number of other dishes. In many cases other foods contributed to the total calorie content of the meal.

Fat accounted for 43 percent of the calories in the salad-bar menus and 40 percent in the hot meals -- at least 10 percent higher than recommended for a prudent diet. So according to this study, choosing the salad bar as the main course did not guarantee that the meal was lower in either fat or calories.

Q: What is the latest evidence about iron supplements for breast-fed infants?

A: A recent study supports the recommendation of the American Academy of Pediatrics that iron supplementation of breast-fed babies should begin in the second half-year of life. In that study, 33 infants were breast fed exclusively and received neither food nor nutritional supplements.

During the first six months, none developed iron-deficiency anemia and only two showed any indication that their reserve stores of iron were depleted.

The lack of evidence of iron deficiency is interesting because calculations of the amount of iron in human milk suggest that it is inadequate to meet the needs of the young infant. One explanation is that healthy newborns have sufficient stores to meet their iron needs. They also may be able to absorb what is available efficiently enough to cover their requirements. But the enhanced availability of the iron in breast milk decreases when solids are added to the diet. That may explain why some studies have shown that breast-fed babies needed additional iron before they were six months old.

Q: Please explain just what molasses is and the differences between the various types.

A: Molasses is the residue left after most sucrose crystals are removed from the concentrated juices of sugar cane or sugar beets. By weight, it contains 70 percent sugars, including sucrose, glucose and fructose, about 25 percent water and a maximum of 5 percent mineral ash.

Beyond that general definition, there are differences in what is available commercially. One kind of molasses is not a "byproduct" of sugar production. It is produced directly from sun-ripened sugar cane and sold as "unsulfured molasses." The sulfur remaining in some types of molasses is a residue left behind when a sulfur-containing compound is used to produce sugar from sugar beets. Blackstrap molasses, an unpalatable component of many folk remedies, is what remains after the concentration of sugar in the syrup is too low to be extracted. Most of it is used in rum production.

Molasses does contain some nutrients besides calories, notably iron and calcium. The exact amount depends on the concentration of the sweetener. Light molasses provides less than a milligram of iron per tablespoon, while the blackstrap variety contains over three milligrams, or 16 percent of the Recommended Dietary Allowance. Similarly, while there are just 33 milligrams of calcium in a tablespoon of light molasses, the blackstrap contains 137 milligrams, an amount comparable to that in a half cup of milk.

Incidentally, the reason that molasses is used with soda as a leavening agent is that it contains some acid. When combined with baking soda, carbon dioxide gas is released.