DEAR DR. BLONZ: Can you help us understand the World Health Organization's (WHO) announcement on cancer and meat? Did the WHO study control for processed meats with and without nitrites? A nutritionist once told me that vitamin C blocks the formation of cancer-causing nitrosamines, and that if I choose to eat bacon, I should also have a lot of orange juice. -- M.C., via email

DEAR M.C.: One study I recall from graduate school revealed that physicians who ate more meat and consumed more alcohol had a one-third lower risk of dying in a plane crash. Does this mean it would have been beneficial to encourage doctors to grab a burger and a beer before they boarded a flight? Needless to say, we need to understand a plausible mechanism before we can give full credence to any population study.

The announcement from the World Health Organization provides useful, but not surprising, information. At the same time, it reflects problems inherent with population studies that extract and correlate data on the impact of a single class of food. With such efforts, there is no way of knowing what was in the rest of people's diets, or the general health status of the individuals from whom the data was collected.

The WHO pronouncement, which covered meats in general, came after a review of hundreds of studies, each with its own methodology. There was a comparison, on a spectrum of health statistics, between people who ate no meat and people who ate lots of it -- and everyone in between. Find a significant difference along that gradient and you have an "association" to report between the level of meat intake and the risk of disease.

Here, we must ask if the key factor is all meat, or only processed meats. Or, does meat only become an issue when paired with a less-than-optimal intake of healthful foods? Or a progressively unhealthful, more stress-filled lifestyle? Or an interaction of these and other factors? It is difficult to control for such fine points, and population studies are not able to report cause and effect.

It is predictable that, analyzing the spectrum from no- and low-meat intakes up to hefty daily doses of the stuff, a general theme would emerge that excessive meat consumption is risky business. Many news stories left off all qualifiers and simply pronounced that "meat causes cancer," period.

A healthful diet, lifestyle and attitude are powerful mitigating factors against potential negatives, but when it comes to food, there is only so much room in our stomach. If meat is on your menu, then enjoy it, keep a handle on the portion size and don't lose sight of your plant-based, whole-foods perspective.

As for your mention of preservatives, fresh meats are less risky than nitrite-preserved meat. Nitrites can combine with the amino acids in meats to form cancer-causing nitrosamines. Vitamin C can help inhibit the formation of nitrosamines, but having orange juice with bacon shouldn't be considered a fix. Routinely having fruit or berries at any meal is always a positive.

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 understand why they put vitamin D in milk, as it aids in the absorption of calcium, which is plentiful in dairy. But why do they put vitamin A in milk? What is the connection? -- R.R. San Jose, California

DEAR R.R.: Nutrients get added to foods in a couple of ways. Enrichment is the adding back of nutrients that were lost during processing, and fortification is the addition of nutrients to a food where they do not normally occur. This addition of nutrients was begun in the 1930s as a practical means to increase the nutritional value of foods, often in response to specific deficiency conditions.

Nutrients were added to foods when typical intakes of that nutrient were below desirable levels for a significant number of people. The foods chosen to be "enhanced" were those typically consumed in sufficient quantities to have the desired effect in the target populations (and not represent any danger for excessive consumption by others). The reliance was on staple foods, such as cereals, milk products and salt.

Finally, the nutrients would have to be added in a form that would be stable and could be easily absorbed. Vitamin D, and later vitamin A -- two fat-soluble substances -- were added to dairy products mainly because they were thought to be the best vehicles for these nutrients.

DEAR DR. BLONZ: I am reluctant to try shortcuts, but I wanted information on the latest product claiming to help people "lose weight without dieting or exercising." It is called chitosan, and there are videos all over the Internet and infomercials on TV. One has a person talking about taking it before a big fatty meal, and your body won't absorb the fat. -- F.S., Austin, Texas

DEAR F.S.: Chitosan is derived from chitin (KITE-un), a component of the shells of crustaceans, such as crab, shrimp and lobster. Chitosan has an ability to bind with fat in the stomach before it has a chance to be absorbed. The chitosan-bound fat travels through the digestive tract and is eventually eliminated from the body in the feces.

If there's an upside to chitosan, it's that fewer fat calories get absorbed. There are estimates that each gram of chitosan can absorb four to eight times its own weight in fat. This means that a 250-milligram capsule could prevent the absorption of 1-2 grams of dietary fat (9 to 18 calories' worth) -- assuming that the fat is in the digestive tract along with the chitosan.

The negatives are that chitosan is not selective in the fatty substances it binds to. That means that it has an equal ability to grab onto beneficial compounds such as fat-soluble vitamins, valuable phytochemicals and omega-3 fatty acids. One study found that a high intake of chitosan led to a rapid decrease in the blood level of vitamin E.

It is also plausible that chitosan could interfere with the absorption of medications where the active component is a fat-based substance. Steroids, birth control pills, hormone replacements and many cholesterol-lowering medications, for example, could be at risk.

Finally, given that the unabsorbed, chitosan-embraced fat passes into parts of the digestive tract where dietary fats rarely go, there may be side effects like discomfort, intestinal gas and diarrhea. Keep in mind that chitosan -- or any other supplement -- does little to influence healthful eating habits, which are the key to long-term success.

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: 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.