DEAR DR. BLONZ: There are always discussions this time of year about the annoyance of mosquitoes and how I seem to be their favorite target. A while ago, I was advised to take 100 milligrams of vitamin B1 twice a day to help repel the critters, and it seems to have worked. I received similar positive feedback at the time from others when they tried it. But I am now concerned about whether this is something I could recommend for my 10-year-old granddaughter, who is about to head to overnight camp. -- S.F., Anderson, South Carolina

DEAR S.F.: Some people seem more attractive to mosquitoes than others. To make oneself uninviting to mosquitoes would be an asset, no doubt. There are anecdotal reports that some people achieved benefits from taking vitamin B1 (thiamine); however, these are casual reports and not the result of any rigorous, objective data collection. To achieve any level of reliability, studies examining the efficacy of a mosquito repellant should compare the treatment with an inactive placebo in a blind study.

Thiamine had its moment, but objective, double-blind studies failed to affirm that it works to prevent mosquito bites with any reliability. You asked whether to recommend thiamine for your granddaughter at camp. The RDA (recommended dietary allowance) for a 10-year-old is 0.9 mg per day, so the 100 mg twice-a-day regimen you mention represents a megadose -- 222 times her recommended level. So the answer to your query is "Nope, not recommended." I'm glad you asked.

Unfortunately, no dietary supplement has proven effective at repelling mosquitoes. Mosquitoes and other biting insects are attracted to perfumes, food and brightly colored clothing. Eliminating stagnant water -- which is a mosquito breeding ground -- from around your house and yard can help. (For more information on how to choose an insect repellant, check out b.link/vtpbxnf. If possible, get a sample before purchasing a repellant, as some people find certain scents to be disagreeable.)

DEAR DR. BLONZ: I have read articles that say combining calcium with vitamin C at the same meal is not good, as one counteracts the other. This notion creates a problem for me at breakfast. I like to enjoy my fresh-squeezed orange juice with a serving of yogurt or cottage cheese. If these nutrients are incompatible, why are some orange juices fortified with calcium? I appreciate your answer. -- D.W., Scottsdale, Arizona

DEAR D.W.: No incompatibility here; these nutrients go well together. If anything, the vitamin C helps keep the calcium in solution and facilitate its absorption.

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 reasonable that pharmacists filling my prescriptions are trained in drug, nutrient and supplement interactions and that I can expect them to alert me if there are potential problems? What if I get my prescriptions filled at a large chain drugstore? -- D.N., Walnut Creek, California

DEAR D.N.: Clinical knowledge in such interactions is expanding as researchers continue to collect pertinent information. All parties involved in your health care should be aware of how a prescribed drug works in your body.

A pharmacist's approach is shaped by the school where they received their training, as well as the pharmacy's policies. In some cases, a patient will receive their prescription along with multiple pages of accompanying information that can be daunting to read through. At some pharmacies, you may not get a consultation with a trained pharmacist unless you request it.

I work on faculty at the University of California, San Francisco (UCSF), and its Doctor of Pharmacy degree students learn how medications work, along with possible interactions with other drugs, supplements and health conditions.

Health professionals must ask the right questions, and patients and their caregivers must provide complete information in response, so that the best care can be offered. Pharmacists may need to contact the prescribing physician for clarification when conflicting medications are prescribed. (Read more about how common medications interact with essential vitamins and minerals at b.link/tvvyrxfl. Online drug interaction checkers are available; inquire with your pharmacy chain, or check out b.link/quwac8.)

We must act as our own health advocates, which includes making a complete list of concerns to discuss with those entrusted with our health care.

DEAR DR. BLONZ: I read about a company that sells water-soluble minerals that they promote as angstrom-sized, elemental minerals that are 99% pure in water. If true, wouldn't this be a far better way to get our minerals? I hope you can help shed some light on this subject for me. -- W.P., Anderson, South Carolina

DEAR W.P.: The angstrom is a tiny unit of measure (1 inch = 254 million angstroms) named after a Swedish physicist that is often used for measuring wavelengths of light. The promotion of the product you mention smacks of sales-talk puffery with little clinical evidence affirming that this form has been shown to be significantly better than others on the market.

Our bodies absorb minerals from foods -- people have been doing that for centuries! A healthful diet is primary, but a wide variety of mineral supplements can help fill any nutritional gaps. Don't be swayed by products promoted with such confusing language. Demand evidence from independent researchers -- ones who don't stand to profit from the sale -- before you buy.

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'd like your advice about shopping for fresh carrots. I tend to like those with fresh greens attached, but I read in an organic gardening magazine that when carrots are pulled from the ground, it's best to break off the tops as soon as possible. The article said that this preserves the nutrients in the root -- which is the part we eat -- because the plant pulls nutrients to the top and away from the root. Is it best to pick carrots with or without tops? -- L.L., Fresno, California

DEAR L.L.: We want a fresh carrot, and we also don't want the tops on for an extended period. Carrots that are slender, firm, bright and moist from periodic watering tend to be best, as opposed to large, tough, woody-looking ones. Carrots with healthy-looking tops indicate they're freshly picked -- these are usually iced and rushed to market. Otherwise, the tops wilt. As for carrots without tops, you have no idea how long those have been around.

A good option is a high-volume produce market that moves a lot of product, where you can have confidence that even the packaged, refrigerated fresh produce is not on the shelf too long. If packaged carrots without tops are your only option, check the stem ends for any spoilage, and ask the produce clerks how long the various carrots have been on the shelf. (Check b.link/vpzar8z for more on how best to store carrots at home.)

DEAR DR. BLONZ: I started taking Pycnogenol, as I thought this "miracle" antioxidant was the best for whatever ails you. I just heard that this might not be the case, and I wanted to ask what you thought. -- P.P., Seattle

DEAR P.P.: Pycnogenol is the trademarked name of a naturally occurring antioxidant substance derived from a maritime pine tree. I don't know the extent of what you heard, but it is dubious to suggest any substance is "the best" for anything that might ail you.

The key to health, good nutrition and effective antioxidant protection is to have naturally occurring teams of substances working together, which is what you get when your diet combines a variety of whole foods, each having evolved its own formula of protective substances. Our bodies produce their own antioxidant substances, but those systems rely on a diet that includes fruits, greens and other vegetables.

While supplements can help, well, "supplement" your food intake, the foundational focus to battle "whatever ails you" should be your healthful diet, as opposed to any "miracle" substance.

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.