DEAR DR. BLONZ: I keep reading and seeing videos about the benefits of colon cleansing, speaking of it in the most glowing, essential-for-good-health terms. I cannot imagine this is something that you would advocate, but want your opinion on the topic. Is it beneficial? Is it safe? -- F.S., Las Vegas

DEAR F.S.: The goal of advertising is to motivate an individual to buy. Objectivity and accuracy can be spun, or bypassed outright when there is no evidence to support the claims.

There are many names for “cleansing” procedures designed to purge the contents of the large intestine, otherwise known as the colon. Aside from “colon cleansing,” these terms include: high colonics, colonic irrigations, coffee enemas, detoxification therapies, and hydro-colon therapy. Some work from the top down, using laxative products and dietary supplements, while others go from the bottom up, relying on the insertion of a rubber tube inside the rectum to flush out the colon with water or other liquids.

What kind of message could make such a procedure attractive?

First, advertisers must convince audiences that there is a problem to be solved, before offering their product or procedure as the solution. Consider that we cannot see what is going on inside our colons. This leaves us open to the suggestion that all sorts of toxins, parasites and other undigested waste are trapped inside. “Impacted” is often an operative word. We get told that an unclean colon prevents needed nutrients from being absorbed, and can divert the attention of the immune system, leaving us vulnerable to a host of ailments. A list of common conditions usually follows, including: constipation, excess gas, irritable bowel syndrome, muscle aches and pains, headaches, depression and fatigue. And of course, colon cancer is often mentioned.

The cleansing procedure gets portrayed as an essential adjunct to the intoxications wrought by our polluted environment and the standard American diet. Add a few pictures, a bunch of glowing testimonials and you have your recipe for a sale.

The first recorded mention of colon cleansing comes from ancient Egypt, and the procedure has had periodic revivals throughout history. It became popular in the United States in the 1920s and 1930s, but as medical science gained a better understanding of the functions of the digestive system, there was no scientific evidence that the routine use of such procedures could help against disease or contribute to long-term health. Today, however, the internet is “impacted” with dubious commercial sites delivering the above scenario and offering products for sale with little in the way of content oversight. You can even find these products at local food stores, next to the dietary supplements.

As to the facts, we all need to appreciate that the cells that comprise the lining of the intestines are shed periodically, which means that the lining of your intestine changes on its own from month to month. This lends doubt to the rather gross concept that caked-on toxins hang around our colon to wreak havoc with our health. Consider also that, except for water, the nutrients in our food get absorbed before they reach the colon.

There is no question that regular bowel movements are an important part of good health, but “regular” can vary from person to person. The whole foods and fiber we eat determine how well our digestive and elimination systems work, and should therefore be viewed as an essential part of our daily diet.

It is our foods and lifestyle that determine our state of health. All this makes more sense than relying on unproven, archaic “flushing” procedures. Read more about colonics at tinyurl.com/j4k7xdm. And here is a link to FTC dealings with a purveyor of these products: tinyurl.com/y9pm4nyj.

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: You have written about different methods of cooking and how they affect a food’s nutrients, but can you talk about how boiling, roasting, microwaving and frying compare? -- K.B., Las Vegas

DEAR K.B.: As a general rule, the longer the time from field to plate, the more nutrients fresh foods will lose. Cold can slow down this process, but it’s heat that serves as the prime nutrient destroyer. The greater the heat and the longer the time of exposure, the greater the nutrient destruction.

Minerals are the only nutrients that are unaffected by heat. Proteins, carbohydrates and fats have a reasonable degree of heat stability, but they, too, will succumb if the heat is high enough. Vitamins tend to be the most vulnerable nutrients, with water-soluble vitamins being the most affected. Vitamin C, thiamin and folic acid, for example, can be destroyed by heat; fat-soluble vitamins can also be destroyed by extended cooking times. There is less data on other plant chemicals (phytochemicals), but it is probable that they would be vulnerable to heat destruction as well.

A list of cooking methods from quickest to slowest might look something like this: microwaving, sauteing, stir-frying, pressure-cooking, steaming, deep-fat frying, roasting, broiling, boiling and baking. Cooking times, of course, can vary from food to food.

Look at potatoes, for example. Because it is cooked rapidly, a microwaved potato will have the greatest amount of vitamin C, whereas a baked potato will have the least. A boiled potato will fall somewhere in the middle.

Nutrients can be lost in ways other than outright destruction. The use of water with boiling can pose a problem, in that some nutrients will dissolve in water. If the water is then discarded, these nutrients are then lost in addition to those destroyed by the heat. Steaming and pressure-cooking also use water, but it’s less of an issue because less water is used with these methods.

DEAR DR. BLONZ: In a recent column, a reader remarked, when comparing lemon juice with vinegar, that the latter took their breath away. This is because the acetic acid in vinegar is volatile, and the citric acid in lemon juice is not. Vinegar can be “tasted” by both the nose and the tongue, whereas the citric acid in lemon juice is only tasted by the tongue. A useful feature of vinegar’s volatility is that it can be reduced in a recipe if it’s too strong simply by heating with the lid off.

This is from a chemist who has smelled a lot of things in his career. -- M.M., via email

DEAR M.M.: Thanks for your helpful comment. As you correctly point out, it is important to consider all the senses when considering a flavor impression.

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: Are corn chips, bean chips or any of the other types of fried vegetable chips any better for you than plain potato chips? There is a definite split on the answer in my group of friends. The Nutrition Facts panels on the packages are not much help. Who is right? -- G.G., Claremont, California

DEAR G.G.: Sorry to confound your quest for an absolute winner, but among the contenders you cite, this one is a bit of a draw. The chip family continues its population explosion, perhaps because it represents such a “value added” enterprise for the manufacturer. There is some nutritional progress, in that all these products must now reveal any trans fats along with the other substances and ingredients. With few exceptions, however, the new members, at least those in the fried-chip family, do not stray that far in terms of nutritional assets.

Corn or bean chips will be slightly higher in some nutrients, while potato chips will have more of others. But neither would be considered good sources for any of the essential vitamins, minerals or fiber. As such, neither should claim to be “better” for you. These are snack foods, not items that deserve consideration for the center of the plate.

Aside from potato and corn chips, you can now find chips that are made from vegetables such as black beans, carrots, spinach, taro, plantains, bell peppers and beets. These vegetables are usually present in small proportions, and usually in combination with corn. Their strong colors lend eye appeal and a novel marketing angle. Fruit chips are also available: apple, pear, peach, banana and more. If these catch on, bits of the entire harvest may find their way into the deep-fat fryer.

All chips share a large surface area, so regardless of their lineage, a deep-fat fry will leave them with that caloric residue -- discernable on your hands when you eat them. If there isn’t any nutritional information available, you can estimate 7 to 10 grams of fat per 12- to 15-chip serving. If you find yourself drawn to chips, opt for those made with a non-hydrogenated canola oil, peanut oil or high-oleic safflower oil.

Fried chips remain the most popular kind, but there are new lines of baked chips to consider. When made from whole foods, they may be worth a try. Whenever dealing with chips, be sure to check the level of sodium per serving.

As always, I recommend the whole food over a chip made from its parts. The whole food provides the fiber and all the phytochemicals the plant produces to assure its continued survival; with chips, we get an extract formulated to provide an attractive appearance, taste and texture that holds together as a thin layer. To see what you are missing, visit the USDA database for any given whole food (ndb.nal.usda.gov/ndb), then compare that with the equal weight of the chips you are considering.

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.