DEAR DR. BLONZ: My favorite catalog advertises a "fat freezer" to reshape your body by destroying and dissolving fat cells. You apply fat-freezing pads on your problem area and select a 30- or 60-minute session. The cooling process decreases fat cell temperature and will naturally eliminate the fat cells from the body. I haven't ordered it yet, but wanted to know if it could be real. -- S.F., Charlotte, North Carolina

DEAR S.F.: Glad you asked first, as it's a dubious approach that comes with risk. Most on point, this type of treatment does not eliminate fat from the body. The cold treatment, called cryolipolysis, can affect fat cell structure and liberate stored calories. But this is liberation, not destruction; the fat will travel through the blood and find a home elsewhere. Understand that there is no app to tell the fat where to go, so what if it ends up in the wrong neighborhood or leaves you with a misshapen body?

There have been some legal issues with this as a commercial technique administered by trained individuals (see b.link/Pudbhx), but you are asking about an at-home device where all you would have is an instruction booklet. I know it's corny to end this with a note to "cool it," but that does reflect my advice.

DEAR DR. BLONZ: Fast-food chains and processed food manufacturers often project caring and wholesomeness in their marketing messages, but this remains a source of puzzlement for me, given they sell foods that shorten the lives of their customers. Why not only promote healthy, nutritious foods that will have customers living longer so they can buy more of their products? -- T.T., Phoenix

DEAR T.T.: The business logic here is not linked to the long-term health of their customers; these are companies selling products with business models based on profits. To succeed, they need to attract customers and provide what they want. It is wonderful to imagine people being more interested in sustainably produced foods that contribute to their long-term health as well as the health of the environment. If that were the case, companies would line up to please those customers, but that's not our reality.

As we make multiple daily decisions about what to eat, occasional consumption of less-healthful fare should not be a significant issue. It becomes problematic when such foods dominate one's diet. Change can be difficult; a better approach would be education that begins in childhood. Even better, have it begin with parents-to-be. There is a need to have an appropriate model in place in the home; remember that it will likely fail if it becomes a "do what I say, not what I do" situation. We should also encourage nutrition and health education courses to be offered throughout the school years, including growing vegetables in school gardens, cooking classes, and healthful, tasteful foods offered at school.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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 it true that raw foods still have their enzymes intact, and that when we eat raw foods, the body uses those enzymes to aid digestion? If so, does this mean that our body doesn't need to rely as much on its own enzymes, giving raw foods a net benefit to our digestion as we age? I have read this idea on food blogs, but it does not make sense, given what I recall from your columns. -- S.F.

DEAR S.F.: Enzymes are compounds that change other substances without being changed themselves. In our bodies, enzymes facilitate the disassembly of complex foods into their component parts before absorption. It's different in plants, where enzymes help make substances available for growth, reproduction or defense.

While plant enzymes don't help our digestion or absorption, they continue to act after the plant's harvest and hasten food breakdown. Refrigeration can slow this action, so many foods benefit from a chill during storage. It is not always a good thing; fresh tomatoes, for example, do not benefit from refrigeration, having a cold-activated enzyme that makes them mushy and less flavorful. (Visit b.link/ub6tzw for more about foods and refrigeration.)

A healthy human body has a cadre of enzymes tailored to our needs. Most enzymes act in the small intestine, where digestion and absorption occur; plant enzymes are not essential to these processes.

The "raw" food idea relates to the fact that cooking can deactivate plant enzymes. But this is not the only risk plant enzymes face: After being swallowed, foods go into the stomach, exposing them to a highly acidic environment that prepares complex foods for enzymatic disassembly in the small intestine. Enzymes are typically proteins, and are denatured by stomach acid like other proteins. Another benefit to stomach acid relates to the fact that foods are not sterile, and the acid helps destroy microorganisms before they can cause harm.

While there can be exceptions for specific foods, sensitivities and health conditions, the general rule is that a healthy human body makes all the necessary enzymes to digest and absorb food. Enjoy raw foods, but not because of any special enzymatic powers.

DEAR DR. BLONZ: I think the newspaper edited your recent column on olive oil to remove the answer to the reader's specific question. The question was about the differences in health benefits -- not flavor -- between extra-virgin olive oil and standard olive oil. Please consider a follow-up column on this. -- A.M.

DEAR A.M.: That was my gaffe, not that of the editors. Please allow me to follow up now.

Extra-virgin olive oil (EVOO) is a healthful adjunct to our foods. The less processed the oil is, the greater the amount of phytochemical assets it contains: substances that evolved to protect the olive and its seed from potential assaults such as the oxidizing rays of the sun. Plentiful evidence suggests that these substances can be beneficial for us, as well.

EVOO is the first oil pressed out during processing, and as such will have higher levels of these assets. For more on olives and EVOO, see b.link/7ea4n4.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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 hope you can clarify information about magnesium supplements on the market, including the hype that most are deficient, that it is a root cause of common ailments and the many promotional claims that their form "is the only one to get." -- H.N., Tulsa

DEAR H.N.: Magnesium, a major essential mineral in the body, is a key player in nerve transmission, the body's use of insulin and carbohydrate metabolism, muscle relaxation, normal heart rhythm, blood pressure regulation and overall cardiovascular health. The body needs magnesium to convert vitamin D to its active form, and, finally, magnesium is also needed for bones and teeth, with more than half found in our bones.

Plant-based, whole-food diets provide good amounts; sources include nuts, bananas, legumes, whole grains, avocados, dark leafy greens, milk and oysters. The recommended intake for magnesium is 420 mg per day.

Be aware that stated requirements take into account the efficiency of absorption. For example, if 30% of mineral compounds tend to be absorbed, a daily "requirement" of 1,000 mg would reflect that the body requires 300 mg (30% of 1,000) of that mineral.

You ask about the variety of magnesium supplements on the market; the essential concept is that whatever form it's in when swallowed, the magnesium that gets absorbed is all the same. Several forms compete for our attention, often promoted with exorbitant sales-talk claims. At issue is the ease with which magnesium separates from the compound it's bound to; that helps determine the amount of time the magnesium is in solution and available for absorption. Remember that a magnesium supplement consumed as part of a meal gains the advantage of the slower movement of the meal's bulk. In such cases, slight differences in solubility may not translate to meaningful differences in overall absorption.

As for magnesium's forms, oxide, sulfate and carbonate are less soluble; these do best if taken with a mixed meal. The more soluble forms include magnesium citrate, orotate, gluconate, aspartate, malate, lactate, chloride, taurate, l-threonate and glycinate (because glycine is an amino acid, this form gets referred to as "chelated" magnesium). Some products offer a variety of forms. Again, absent clinical evidence, do not be enticed by promotional claims of exorbitant superiority of one over the other.

Among the least soluble are magnesium oxide and magnesium hydroxide; the former has water-absorbing effects that can help soften hard stools and gets used in laxatives; the latter has acid-neutralizing abilities and is found in OTC antacids. These are not the best options to up your intake of magnesium.

The kidneys are critical to eliminating excess magnesium, so check with your health professional before taking supplements if you have renal issues. The important flip side is that when intakes fall below the recommended levels, the kidneys can help by limiting the amount lost in the urine. This tends to be the case with many nutrients, meaning there is no need to get frantic with occasional lower-than-recommended intakes. However, low magnesium intake for a long period can lead to magnesium deficiency. Those with gastrointestinal disorders, type 2 diabetes, or alcohol dependency issues, as well as older adults, can be at increased risk for magnesium deficiency.

It is best to be sure foods providing this essential mineral have a regular place in your diet; again, discuss the advisability of taking supplements with your health professional. Don't be swayed by overstated claims of clinical superiority of one soluble form over the other. I use "clinical superiority" in this advisory. While studies might show a few more milligrams absorbed of one soluble form of magnesium over another, this should not be assumed to impact the risk of disease (clinical significance). Getting the recommended amount of magnesium is the goal here. Check the National Institutes of Health magnesium fact sheet at b.link/979bks.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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.