DEAR DR. BLONZ: As a teacher, I am concerned about what some parents give their children for lunch at my school. When I ask the children, some say that they have these types of foods at home, as well. I have been given the go-ahead to develop a nutritional lesson plan that involves doing a blog for the parents. What are your thoughts on highly processed foods for children? -- M.L., Oakland, California

DEAR M.L.: Highly processed children's meals are not the stuff on which long-term healthy eating habits are established. It is less of a problem if we are taking about whole foods that are minimally processed, such as drying or freezing fruits and vegetables. But if sweetened snacks and fabricated "foods" tend to be the routine rather than the exception, it's time for a reexamination of priorities.

I think the blog is a great idea, but I would proceed cautiously. The idea is to enlist, not alienate. One strategy I used, when speaking to students at my son's middle school, was to scan the labels of children's favorite foods with them. I went through the ingredients, explaining which were good for them and which were not (and all the various ways of naming "sugar"). The outcome was that the children went home and started lecturing their parents on ingredients! The lesson can be eye-opening, and also quite entertaining.

A child's interest in healthy eating really should be home-grown, so to speak. In your lesson plan, you might consider sharing ideas that involve the whole family. For instance, parents can get kids involved in menu planning: Discuss options for upcoming meals, and ask for input. If there is more than one child, they can take turns helping to plan meals.

Asking children to name their favorite vegetables or fruits, and then letting them pick them out at the market, may increase the odds that they'll eat them. Parents also need to have kids help with meal preparation, whether it's making a lunchtime sandwich, helping measure ingredients or simply arranging food on a serving plate.

Whenever possible, take kids along on shopping trips; just make sure they've been fed beforehand. At the grocery store, children are on the receiving end of a tremendous amount of marketing -- cartoon-character promotions, end-aisle displays, colorful package designs, kid's-eye-level placement of snack foods -- all designed to influence them, and consequently, their parents' purchases. A full stomach can help them navigate this manipulation, as can their new knowledge from your blog.

All these efforts will have greater chances for success if they are designed to work together, and if the parents are on board. Lessons about the nutritional value of various foods, and their importance for growth and good health, can provide a foundation to establish healthful habits for life. I applaud your energy and wish you well in your efforts.

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: A friend told me to take guarana pills for alertness, better concentration and faster learning. I've also heard that guarana is used as a cure for impotence. What can you tell me about it? -- D.P., Charlotte, North Carolina

DEAR D.P.: Guarana (Paullinia cupana) comes from the seeds of a South American climbing shrub. The claimed effects you mention, at least those associated with alertness and better concentration, relate to the fact that guarana has a high concentration of caffeine -- over twice that found in the coffee bean, the kola nut or cacao (cocoa). Coffee drinkers view their brew with a degree of reverence for its stimulating effects, but caffeine actually functions as a plant's phytochemical defense to dissuade animals from dining on its seeds.

As regards your statement concerning the other alleged use for guarana, there is no research to support the use of guarana or caffeine to treat impotence.

DEAR DR. BLONZ: I know this is the case with bananas, but do oranges get sweeter and improve in nutritional value as they age? What about color and storage? -- B.B., Baton Rouge, Louisiana

DEAR B.B.: There is no reason to "save" an orange in the hopes that it will improve in flavor or nutritional value. Some fruits, such as bananas or stone fruits, contain enzymes that remain active after harvest, and these enzymes break down complex carbohydrates into simpler, sweeter-tasting sugars. This, however, isn't the case with oranges, a fruit that is traditionally harvested at the peak of ripeness.

What that means is that when it is picked, the orange is as sweet as it's going to be. It is also the time at which the vitamin C content will be the highest. As for color, it may not always be a reliable indicator of ripeness and flavor, as perfectly ripe oranges sometimes carry a greenish tinge. The color of an orange tends to reflect the temperatures in the days prior to harvest.

Although they will keep for a few days at room temperature, it's best to keep oranges in the refrigerator. When an orange begins to shrivel, its nutrient value will have also begun to decline.

DEAR DR. BLONZ: I am hoping that you can weigh in on a debate my son and I are having. I told him that when vegetables are boiled, nutrients evaporate with the steam unless the lid is on. He has dismissed this, saying that all the nutrients stay in the cooking water. -- J.A., San Diego

DEAR J.A.: Your son is much closer to the truth. Although some nutrients are destroyed by heat, they do not evaporate and get carried away in the steam. Those nutrients that are water-soluble and heat-stable will remain intact in the cooking water. The nutrients that don't dissolve in water remain in the vegetable.

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: In my 20s and 30s, I was able to maintain a reasonable weight with diet and exercise. Now, at 43, I have maintained my activity, but have been gradually gaining weight. I now find myself about 15 pounds overweight. I have researched diets and am considering going very low-carbohydrate, but I want to know how this diet is supposed to work and whether it's worth it. -- F.T., Chicago

DEAR F.T.: When you eat a diet that is very low in carbohydrates (under 20 grams a day), you have threatened your body's access to glucose. A chronic shortage of available glucose creates the situation in which your get-up-and-go energy will have, in effect, gotten up and gone.

The fat stored in our body is our major energy reserve, but the body needs small amounts of glucose to help it burn the fat correctly. The incomplete combustion of fats produces ketone bodies, and these can be toxic if allowed to accumulate. The body starts to eliminate them through the urine. The resulting condition, called ketosis, also occurs with uncontrolled diabetes; there, the body is unable to produce the insulin needed to let glucose into the energy-producing (fat-burning) cells of the body.

Certain tissues -- including the red blood cells, the kidney medulla, the lens of the eye and even the brain -- rely on glucose as a primary fuel. When there isn't enough glucose, the body begins to scavenge around for potential sources among its own tissues. The liver has glycogen, a source of stored carbohydrate, and there is a small amount in the muscles, but the amount stored is small in relation to total bodily needs.

Protein can be used, because some of its amino acids can be turned into glucose. The muscles represent the body's largest reserve of protein, and like all protein tissues, they are about 80 percent water by weight. When the body begins to break down muscle tissue to get amino acids to turn into glucose, the water portion of muscle tissue gets released and eliminated. Like magic, the numbers on the scale begin to go down -- but it is water weight, not excess body fat, you are losing. This type of lost water weight is quickly regained once carbohydrates are back on the plate.

The bottom line is that a low/no-carbohydrate diet is a questionable way to lose weight. And besides, who wants to live life without carbohydrates?

It is important to accept that it's not unusual to gain weight as we pass through our 30s, 40s and on up. It's a natural side effect of an age-related slowdown in our metabolic rate, coupled with a trend toward less physical activity as we age. While the former is beyond our control, we can definitely do something about the latter.

A good strategy is to avoid quick-fix fad diets and strive to be the healthiest person you can be. I am certainly impressed by your attempts to stay active, and I hope you are able to keep it up regardless of which dietary path you choose. I wish you the best.

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.