Dear Dr. Blonz, In our house, broccoli is a go-to vegetable due to its availability and relative low cost. I prepare the stems as well as the florets, cutting the stems in diagonal disks so they can get tender when steamed. I am guessing there is less nutritional value in the stems than in the darker florets. How significant is that difference? I.K. Gilroy, CA

Dear I.K.: Broccoli is a member of the crucifer family. Other members of this healthful group include cauliflower, Brussels sprouts, kale, bok choi, turnips, rutabagas and cabbage. All of these contain a number of healthful phytochemicals, but broccoli is high in vitamins A and C and is also a source of vitamin K and dietary fiber.

It also contains sulforaphane, which has been reported to have cancer-fighting properties. Young broccoli sprouts and seedlings are the richest source of the sulforaphane, but the florets are next best. The fibrous stems contain less of the nutrients and phytochemicals, but are a great source of dietary fiber. Your method of preparation allows you to have it all. An item of interest regarding broccoli is that there is an enzyme in the broccoli that helps the sulforaphane form. When the cells are ruptured, such as during cutting, mashing or chewing, the enzyme goes to work, but it can be inactivated by heat. This means uncooked or quickly cooked broccoli will offer more sulforaphane than broccoli that has been overcooked.

Dear Dr. Blonz, I read your column every week and also love all the advice that you give on your website. I read the column about the cooking methods and destruction of vitamins, especially the water-based vitamins. My question is this: I love mixing all kinds of vegetables and making mixed veggie soup. The vitamins of the vegetables that have been ruined -- are they in the broth of the soup, or they are completely gone? Does any percentage of them stay in the broth? Though I love raw vegetables, my digestive system cannot handle the raw fiber, but if I cook them and eat the soup as well, then I am OK. So I hope that I do get some nutrients. Thank you very much. A.S. Oakland, CA

Dear A.S.: There can be losses when there is destruction by heat. In such cases there will less of the heat-labile nutrients once a key temperature has been exceeded for a period of time. (As with the broccoli answer above, longer times equal greater destruction.) There can also be nutrient losses through dilution if the nutrients are water-soluble and the portion that ends up in the cooking water is not a part of the meal. Minerals tend to be heat-stable, but depending on the form they are in and how the food is prepared, some can be lost with the cooking water as well.

It is difficult to come up with specific percentages that remain, but if you eat a healthful, varied diet, I don’t recommend you be overly concerned about these losses. There are usually other foods that provide these nutrients, and oftentimes these other foods represent the primary sources. For example, cooking vegetables may destroy their vitamin C, but it is fruits, not vegetables, that tend to be the major source in most diets. Your vegetables and soup combination sounds wonderful, so don’t sweat the small stuff.

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: I have been advised to bring down my cholesterol, or else I'm going to need to take medication. My wife insists that I cut the cholesterol that I eat, and she makes direct mention of my love of eggs. I am thinking of using cholesterol-free egg substitutes, but find them a bit pricey. As an alternative, I have been buying eggs by the dozen, separating the yolks and saving only the whites. Is this a reasonable way to avoid cholesterol? -- R.R. Palo Alto, Calif.

DEAR R.R.: It is definitely an option. The white of an egg is a source of high-quality protein; it is the standard to which all other proteins are compared. There are approximately 3.5 grams of protein in the white of a large egg. There are small amounts of other nutrients, including selenium, potassium and sodium. The yolk contains lesser amounts of protein, together with small amounts of vitamin A, folate, phosphorous, potassium and selenium.

The eggshell is a great container. As you can tell by the date stamped on an egg carton, whole eggs can usually last in a refrigerator for several weeks before they need to be eaten. Once you open the shell, however, the clock runs at a more rapid pace. Egg whites, out of the shell, have a recommended shelf life of only four days. This is something to consider when opening up a dozen at a time. You might consider freezing the whites in an ice-cube tray. Egg whites can last up to a year when frozen.

You state your desire to watch your cholesterol intake. The yolk of one large egg contains approximately 213 milligrams of cholesterol. For those with an otherwise balanced diet, the periodic use of whole eggs has been shown to have only a minimal impact on one's blood cholesterol level. If you truly have a passion for eggs, having one a day can fit within the American Heart Association's guidelines. A compromise might be to use one yolk for every two egg whites.

It might also be helpful to discuss the connection between dietary cholesterol and the level of cholesterol in the blood. Please bear in mind that this might not apply to your specific case, but in general, the American public has been persuaded to wear blinders that let them see only the fat and cholesterol in their diets as the factors responsible for elevated blood cholesterol and heart disease. This has led to thinking that reducing dietary fat and dietary cholesterol are the best ways to lower blood cholesterol and the risk of heart disease. Things, however, are not that straightforward.

First, consider that lowering dietary fat might lead to eating more carbohydrates, and if that meant a higher intake of sugars, you wouldn't be doing yourself any favors. There's little question that the levels and types of dietary fat and cholesterol can play a role, but they are not the unqualified culprits we've been led to believe. More important is a diet that's balanced and rich in fruits, vegetables, greens, whole grains, nuts, seeds, dietary fiber, etc. These supply the food factors to enhance our health. A body that is healthfully nourished is equipped to handle the fats and cholesterol in the foods it eats.

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: Is guarana better than caffeine, and is it habit-forming? My religious beliefs recommend that I keep away from caffeine. I am 67 years old and retired. Even after a good night's sleep, I suffer from tiredness as soon as I wake, as well as lower leg aches. -- M.J., Provo, Utah

DEAR M.J.: Guarana, in essence, is caffeine. The active ingredient might go under the name "guaranine," but that is just another name for caffeine. Guarana comes from a paste made from the crushed seeds of a woody shrub native to the Amazon region. Caffeine (guaranine), which belongs to the alkaloid family, is the principal active ingredient in guarana. There is a higher concentration of caffeine in guarana than in the coffee bean, the kola nut or cacao (cocoa). Guarana also contain trace amounts of other alkaloid compounds, most notably theophylline and theobromine.

Caffeine, regardless of source, can produce tolerance, psychological dependence and habituation when consumed on a regular basis. Withdrawal symptoms, including headache, drowsiness and fatigue, can occur when intake is stopped abruptly. Interestingly enough, abstinence from caffeine is a very common cause of headaches after one has gone through surgery, as presurgical routines usually require that one stop caffeine. One study published in the Mayo Clinic Proceedings found it beneficial to give a small amount of caffeine intravenously to patients undergoing outpatient surgery who were at risk for caffeine-withdrawal headaches.

Leg aches can be brought about by any of a number of situations. It may be that you would benefit from stretching and flexibility exercises, or there may be some specific medications or even herbs to try. It could even be the bed you sleep on. You need to find out whether there is anything medical going on before you begin looking for methods -- or substances -- to provide relief.

DEAR DR. BLONZ: Please explain the origin of carnauba wax. I find it on candied almonds and other foods. Does it represent a concern as a food additive? -- N.N., Pinole, Calif.

DEAR N.N.: Carnauba wax comes from the leaves of the South American wax palm. It is used as a wax or a glaze and it has "GRAS" status (generally regarded as safe). It is one of a number of such compounds used in foods. Aside from carnauba, there are the oil-based compounds petrolatum and paraffin. Shellac, another commonly used wax, comes from an Asian insect and is also used on candies, jewelry and floor waxes. Carnauba is also used in car wax.

Waxes are applied to hard-coated confections, such as candied chocolates and almonds, but they are also used with produce, including tomatoes, apples, bell peppers, avocados, cucumbers, sweet potatoes, all citrus fruits, peaches, pumpkins, eggplants, squash and nuts in hard shells. In produce, waxes are applied to retain moisture, limit flavor loss and enhance appearance. Waxes are not considered harmful and are only used in small amounts. For example, The Center for Produce Quality estimates that one pound of wax will cover 160,000 pieces of fruit or vegetables.

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.