Q. I saw an advertisement for something called canola oil, claiming it's lowest in saturated fat. What is this oil and, should I use it?

A. Canola oil is produced from seeds of a specially bred variety of rapeseed, a member of the Brassica family of vegetables. Chemically, it differs from other popular oils in that it contains mainly mono-unsaturated rather than polyunsaturated fatty acids. As the advertising copy you read no doubt pointed out, it has less saturated fat (the type that drives blood cholesterol upward) than other oils.

While that is true, just how different oils are depends on how the data are presented. We think it makes good sense to look at them in terms of household portions. And regardless of which oil you choose, a tablespoon provides about 13 1/2 grams of fat. Comparing the amount of that total that is saturated, we find that a tablespoon of canola oil contains about a half a gram less than safflower oil and a gram less than the same amount of soybean oil.

These differences are really nothing to write home about. So if you use oil sparingly, as you should, it seems reasonable to let taste preference be your guide.

The name "canola," incidentally, was chosen in 1978 by the Canadian seed-oil industry to describe the new variation on a very old product. The plant from which oil is derived is a relative of one used in ancient Asia for lamp oil and in 13th-century Europe to feed cattle.

Q. Is it healthier to fry foods in cold-pressed safflower oil or in 100-percent virgin olive oil?

A. Our first response is to suggest that you fry as little as possible in any oil or fat, whatever the kind. Fat used in cooking doesn't add much besides calories -- and a lot of them, at that. For most of us, those calories are far in excess of what we need to meet daily energy requirements.

As for the terms "cold pressed" and "virgin," both describe methods of processing that do not affect the nutritional merits of these oils significantly. Our advice, then, is that when you do decide to fry something, choose the type of oil that will give the results you want.

Making a Chinese stir-fry dish, you would probably prefer the flavorless safflower oil over a fruity olive oil. On the other hand, olive oil might be your choice for a Mediterranean saute'. Regardless of the type, use as little as possible. And try to drain off the surplus before setting the dish on the table.

Q. Are low-fat and skim milk recommended for babies? If not, why not?

A. There are several reasons why reduced or fat-free milks aren't recommended for infants. Skim milk, in particular, is simply calorically too dilute. More than a decade ago, Dr. Samuel Fomon and his colleagues at the University of Iowa demonstrated that when a group of male infants were fed as much skim milk as they wanted, they consumed a considerably greater volume than infants fed standard formula. However, they still consumed fewer calories. The result was that they grew at a slower-than-normal rate and had far smaller fat stores than would be expected. In fact, fat stores were 25 percent below normal.

Information about what happens when older infants are fed skim milk is more limited. What data do exist indicate that their intake of linoleic acid, the essential fatty acid, may be below recommended levels. Also, the percentage of calories that come from protein may be quite high, causing unnecessary wear and tear on the kidneys.

Unfortunately, studies comparing the growth of infants fed 2-percent milk with those fed whole milk suffered from flaws in design. In another study, infants fed 2-percent milk did manage to consume as many calories as those given whole milk or formula, but to do so they too had to imbibe a considerably larger volume. The result is that they took in more protein, as well as more of several minerals, again putting an extra burden on their kidneys.

And at younger ages, their fat stores were lower than those fed milk of normal fat content. Indeed, the bulk of the evidence suggests that as infants grow a bit older, they are increasingly able to compensate for the diminished energy content of reduced and fat-free milk by taking in a greater volume of the milk as well as more solid foods.

But the point is: Why challenge them to do so? For the first year of life, breast milk or fortified formula are the preferred choices.

Q. I can't find ground lamb in my local market and would like to grind my own. What part of the lamb is best for grinding?

A. Since it is to be ground, cost and not tenderness is usually the first consideration. Where it is available, ground lamb is generally made from meat in the shoulder area and other trim. Shank meat, stripped of tough sinews, can also be used. Some Middle Eastern markets also grind lamb leg for raw kibbe. Cost notwithstanding, because of the potential dangers of food-borne illness, we strongly caution against eating uncooked meats of any type.

Lamb, especially the cuts you'll be using, is high in saturated fat. We suggest you trim the meat carefully before grinding, and adapt the recipe so that you can drain off as much fat as possible during cooking. For example, in making baked kibbe, a ground lamb and bulgur wheat dish with pine nuts, we use a bulb baster to drain the excess fat as it renders while cooking. And after grilling ground lamb patties with yogurt and mint topping, we drain them on paper towels to eliminate as much of the extra fat as possible.

Q. Because I suffer from osteoporosis, I take a prescribed calcium supplement, as well as a daily multivitamin. I've always liked water and drink eight to 10 glasses a day. My cousin suggested that by drinking so much, I'm causing the calcium and vitamins to be flushed out of my body instead of being absorbed. I'm 77 years old and I hate to change a longtime habit. Do you think I should?

A. No, and your concern illustrates the common hazard of getting well-meaning but inaccurate advice from friends or relatives. In the first place, the amount of water you drink isn't excessive, especially if that's your main source of fluid replacement. It's essential to take in enough water to maintain fluid balance. A good supply of liquids also helps dilute urine and may aid in preventing kidney stones and urinary tract infections. Insufficient intake can increase fluid absorption from the gut and cause problems with bowel function. So drink up.

There's no need to worry about losing nutrients. The amount of water-soluble nutrients that get flushed out in the urine doesn't depend on how much water you drink. Rather, it's related both to your body's ability to absorb a particular nutrient and to how much you're consuming relative to your need. For instance, if you've filled your quota for, say, riboflavin, and your body has absorbed all it can store, the extra will be excreted in your urine. It's like a gas tank overflowing if you fill it too full.

Q. A friend recently served lobster at a dinner party. When I separated the tail from the body, I was startled to see a greenish-black, oily, sticky material on the tail meat that looked most unappetizing. Two of the five guests at the party had the same thing. Since this experience was new to us, we were concerned about whether the meat was safe to eat. However, we rinsed it before eating, and no problems occurred. Did we do the right thing? What is that greenish slime?

A. Don't worry, the meat was safe, even though it looked unattractive. The phenomenon you observed is related to an imbalance between a lobster's ovarian cycle and its molting cycle. Normally, female lobsters carry their eggs in the tail section for nine or 10 months. In the molting cycle, the lobster sheds its shell for a larger one. But if this cycle is not properly synchronized with the ovarian cycle, the eggs are not released. The greenish-black, viscous material, which gets its color from a protein called lipovitellin, is simply the unreleased eggs.