DEAR DR. BLONZ: Will meal-replacement bars work well for a multiday backpacking trip in the mountains? It will only be for a few days, and I am thinking of taking bars instead of freeze-dried food. Some bars try to be balanced meals, while others are only slightly better than snacks. Assuming I have plenty of water, do you foresee any problems relying on them for a few days at 10,000 feet? -- M.H., Indio, California

DEAR M.H.: My response assumes you are in appropriate shape for such a trek, that you have been fully acclimated to high-altitude hiking, and that the only issue is what you would be eating. That said, an approach based on real food would be preferable, as it offers a wider variety of flavors and textures.

You might find that after living off of meal bars for a few days, they’ll all begin to taste alike, and mealtime will lose its appeal. You could do a mix of bars and regular meals to see how it works out on the trail. But this is a short-term issue, so I can see no serious issues if you want to focus on sports bars.

Sample all prospects in advance, as you may not find all of them to be pleasing to your palate. You will be exhausted after hiking all day, and will want something satisfying to eat. Find an assortment that brings together sufficient energy (calories), high protein and a balance of nutrients. Select some designed for exertion and others designed to be meal replacements. Have a variety of products so that you won’t get bored.

Consider supplementing this selection with foods such as jerky, nuts and dried fruits. These will bring concentrated energy, nutrients and variety -- the latter providing a welcome hedonic boost. Add sufficient fluids, and you will be all set.

It’s only two or three days; the key is to bring along enough calories and nutrients to facilitate, rather than impede, the outing.

DEAR DR. BLONZ: Tell me a bit more about xanthan gum. I have a corn allergy, and recall you writing that xanthan gum is made from corn. It is my understanding that it is the end product of a fermentation process involving Xanthomonas campestris, which is mainly “fed” corn syrup as its source of sugar. These are gum-producing bacteria, which yield xanthan gum. As such, I am not sure it can be said to be made from corn syrup. -- S.F., Hayward California

DEAR S.F.: Much in the same way that we might think of beer as being “made from” grains, it is not that misleading to think of xanthan gum as coming from corn. That earlier column had been generated from a reader’s concern about a corn allergy, and I adapted the answer to fit that paradigm. To be more precise, consider that xanthan gum, a preservative used to help thicken and stabilize foods, is made “using corn.” It is refined, and this should, in theory, remove any corn protein. But that represents an unknown for any particular manufacturer, so I counsel avoidance -- or at least awareness and caution -- for those with a corn allergy.

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 am a trainer in San Diego and have heard about an herb that teenagers are ingesting. What are your thoughts on vinpocetine? One website touts that it is in the PDR (Physicians’ Desk Reference) and seemingly safe. But I am worried about anyone, especially teens, using this substance. -- S.T., San Diego

DEAR S.T.: First off, why would teenagers be taking this stuff? Secondly, being in the PDR only means that someone has paid the money to have it listed; it does not equate with effectiveness.

Vinpocetine is a synthetic derivative of a vincamine, a chemical found in the periwinkle plant. Naturally occurring vincamine has a short half-life, but the synthetically derived vinpocetine does not. Work done to date is quite preliminary, but the fact that vinpocetine is synthetic means that it should not even be in a dietary supplement. It’s unclear why the Food and Drug Administration hasn’t taken action.

As a drug, vinpocetine may have an ability to enhance blood flow in situations where there is already a reduced blood flow, such as after a stroke or another type of vascular impairment. To date, all we have is some sketchy evidence from stroke victims, or studies in which a memory inhibitor is given, and then vinpocetine is administered to see if it can counteract the inhibitor.

Use by teenagers or young adults is definitely ill-advised, as there is no information on long-term effects. There is also a paucity of information on potential interactions with medications and unknown impacts on memory development in the young adult brain -- not something you want to roll the dice on.

DEAR DR. BLONZ: To forever snuff out a discussion I am having with a neighbor, please discuss urine therapy. In particular, she is convinced that drinking her own urine is what contributes to her beautiful skin. She has several books claiming this to be a legitimate treatment, but my understanding is that urine is a waste product and should be eliminated by the kidneys. -- R.B.

DEAR R.B.: Here’s hoping you can find a neighborly way

to say, “yuck.”

You are correct that urine is a waste product. It is mostly water, but also contains substances that the body is purposefully eliminating in its attempts to maintain balance. Urine will also contain breakdown products from hormones, metabolic waste products, drugs, toxins and other foreign substances. Urine is also one route by which the byproducts of bacterial infections are shown the door; as such, ingesting it is a risk for anyone suffering from an infection.

I also found some mention of the idea of cosmetic benefits from drinking or washing with urine. But finding it mentioned doesn’t make it true. I could find no objective evidence in support of the idea.

Let us say, for the sake of argument, that there is some unidentified beneficial element in urine. Consider that when you consume the whole recipe, along with that good element, you get the bad and the ugly. You are also creating an additional burden on your system, as it all has to pass through and find its way out again, taking more of the body’s water as it heads out the door.

This is definitely a circumstance where a flush is the wining hand.

For a more detailed discussion, see b.link/urine84.

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: Regarding your answer about the ability to smell asparagus in urine, you had said “the ability to perceive the odor is determined by one’s genes.” Whose genes? The person producing the urine, or the person doing the smelling? Along this line, my wife seems to have “smell genes.” She accuses me of not bathing and wearing dirty clothes the day after I have eaten a salad with Italian dressing on it. How common are these “smell genes” in the general population? -- F.M.

DEAR F.M.: My apologies for any confusion. A sulfur compound gets produced in all who consume asparagus; it comes from a normal breakdown of the asparagusic acid found in varying levels in asparagus. Certain genes are needed for an individual to detect this odor.

As regards the second part of your question, several alterations can occur in the sense of smell, ranging from anosmia (loss of the sense of smell) to dysosmia (alteration or distortion in the sense of smell) to hyperosmia (enhanced sensitivity to odors). Attention should be paid when there are unexpected changes in the sense of smell (or taste). I’m unsure if the situation you describe is one you have always had to live with, or if it is something that recently emerged. If the former, then the two of you have to rely on your own strategy. But if a change in your wife’s sense of smell (or taste) is something that developed recently, then consider having it evaluated medically. A physician can determine whether it is the product of some event or ongoing process that needs to be better understood. More on this at b.link/taste81.

DEAR DR. BLONZ: I read your advice about the tolerable upper limits of copper and zinc. Currently, I am taking supplements called PreserVision AREDS 2 by Bausch + Lomb. Although I don’t have glaucoma or AMD (age-related macular degeneration), my mother had both. I do have medical issues with my eyes, just not those suffered by my mother.

I am taking one pill a day, though the directions say to take two. Each pill contains 40 milligrams of zinc and 1 milligram of copper. The main reason I’m taking the one pill is that it also contains 5 milligrams of lutein and 1 milligram of zeaxanthin, but now I wonder if the zinc isn’t too much. Should I stop taking them? -- C.E., Freemont, California

DEAR C.E.: A key issue with zinc and copper arises when one is present, and the other is not. This is made worse if one is present in excessive amounts in the absence of the other. The AREDS 2 supplement provides both zinc and copper, so that issue does not present itself.

I thank you for this question, and I hope this serves as a clarification of the point, so that others who might be taking this or similar products will not be concerned. Also, give a read to this article on vision supplements: tinyurl.com/yxmybl7r.

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.