(FORTUNE Magazine) – I realize that Dr. Robert Atkins died, but I keep hearing about his diet. What's up?

There's been a lot of media interest in the Atkins diet recently, but the medical and scientific communities still have questions. Earlier this year two studies in a major medical journal showed that people on low-carb diets lost more weight initially, but after one year there was little difference in weight loss compared with a traditional calorie-controlled diet. While triglyceride levels seem to improve on low carbs, we don't know the diet's long-term health effects on heart disease and cancer. I personally have concerns about limiting the intake of vegetables, fruits, and whole grains, all of which have many proven health benefits.

If fish is so healthy, why should I watch how much I eat?

Omega-3 fatty acids, found in fish, appear to help lower blood pressure, stimulate immune function, and lower triglycerides. As little as two servings of fish a week may help decrease the risk of sudden cardiac death. On the downside, both commercial fish and sport fish contain mercury and contaminants such as PCBs and dioxin. Children and women who are pregnant or considering pregnancy should limit their intake to no more than 12 ounces a week, and the FDA (www.foodsafety.gov) recommends that they completely avoid swordfish, mackerel, tilefish, and shark. Individual states issue advisories on the status of fish in their lakes and rivers, consolidated by the EPA at www.epa.gov/ost/fish.

I was recently treated for "precancerous" skin lesions. What does that mean?

Actinic keratoses are flaky, slightly red skin lesions that often develop on sun-exposed areas such as the temples, nose, face, and arms. They're more common with fair skin and increasing age. Potentially they can turn into cancer, but that takes many years. They're easily treated with some creams or ointments or by freezing with liquid nitrogen. As long as you see your dermatologist regularly, you should be fine.

A relative of mine received intravenous nutrition in the hospital. Can anyone get a periodic IV boost?

No. There can be serious complications with IV feeding. It's also expensive, and there are no advantages over regular food. We use IV nutrition only when someone is too ill or can't eat.

If the PSA blood test isn't 100% accurate, why bother?

The prostate-specific antigen test has helped diagnose many cancers at an early stage --when they're very small and can't be felt during a rectal examination--but interpreting it correctly requires some expertise. If the cancer doesn't produce PSA, PSA levels won't be elevated, and in any event, an elevated PSA isn't always due to cancer. (Infection or enlargement of the prostate can also raise the PSA.)

I have seasonal allergies and have had some wheezing. Could it be asthma?

It's certainly possible. Allergies trigger asthma in some people, and asthma can develop in childhood or when you're an adult. See your physician for testing. Controlling allergies with an inhaler or oral allergy medication, along with avoiding exposures to the triggers, can help manage asthma.

My daughter wants to get her tongue pierced. Is that a problem?

I'm not wild about any type of piercing. Almost 20% of people who try it have complications. Infection is the main issue, particularly for the navel, and bleeding, scarring, contact dermatitis, and even endocarditis (heart infection) have been reported.

Donald D. Hensrud, MD, is director of the Mayo Clinic Executive Health Program. For more on this topic, go to mayoclinic.com. Mayo Clinic offers Executive Health Programs in Jacksonville, Fla.; Rochester, Minn.; and Scottsdale, Ariz.