Archive 2005 2006 2007 2008

Q: Who should take antibiotics before going to the dentist? I’ve heard different recommendations.

A: Far fewer people than were advised to in the past, according to new guidelines from the American Heart Association (AHA). The idea of taking antibiotics before dental procedures is to prevent bacterial endocarditis, a life-threatening heart infection.

It has long been assumed that people with certain heart conditions—notably mitral valve prolapse (a common structural heart valve abnormality)—were at increased risk of endocarditis after dental procedures because bacteria in the mouth can enter the bloodstream if there is bleeding from the gums. But there’s no scientific evidence to support this. Very few people develop endocarditis after dental work. And antibiotics would prevent only a tiny fraction of cases.

According to the AHA, the overall risks from taking antibiotics before dental procedures as a preventive (including allergic reactions and development of antibiotic resistance) outweigh the very small benefits.

However, the AHA still advises that people at highest risk of having serious complication from endocarditis take antibiotics beforehand, including those with an artificial heart valve, valve problems after a heart transplant, previous endocarditis, or specific congenital heart conditions. The American Dental Association as well as the American Academy of Orthopaedic Surgeons further recommend antibiotics for some other people, notably those who have had a total joint replacement in the last two years.

Q: If my husband has shingles, can I catch it? What if I never had chickenpox?

A: No, you cannot catch shingles from anybody. Shingles, characterized by a blistering rash, usually on the torso, is caused by the same herpes virus (varicella-zoster) that causes chickenpox. After you have that childhood disease, the virus stays dormant in your body and can re-emerge decades later, for unknown reasons, to cause shingles.

If you’ve never had chickenpox, you can catch that from someone with shingles. However, almost all older adults have had chickenpox, even if they don’t remember. If you aren’t sure, you can ask for a blood test to find out. Chickenpox itself is very contagious, but the virus is less easily transmitted from shingles patients. Thus, you may not get chickenpox even if you’re exposed to shingles.

If someone who has never had chickenpox (nor been vaccinated against it) is planning to visit, ask him to wait until the contagious stage has passed. Do not expose a pregnant woman who has never had chickenpox to either chickenpox or shingles, since the virus can harm the fetus. If she has had chickenpox, there’s no danger.

Don’t forget: The new shingles vaccine, approved for people 60 and over, will prevent about half of all cases and greatly reduce the severity and duration of shingles if it does occur. You can get the vaccine even if you never had chickenpox; it will protect you from both chickenpox and shingles.

Q: Do calcium supplements cause constipation?

A: Calcium supplements have long been blamed for causing constipation and bloating. But aside from two recent studies that found slightly higher rates of constipation in women who took high amounts of calcium, there is surprisingly little research to back this notion.

Still, if you think that your supplement has that effect on you, try switching the type of calcium that you take. Calcium citrate, for example, may be easier on the stomach than calcium carbonate (in most major calcium brands). And don’t take more than 500 milligrams of calcium at a time (the body absorbs larger amounts less efficiently, in any case). Some drugs used to treat high blood pressure may interact with calcium and cause constipation.

To stay regular, consume more fiber-rich whole grains, beans, fruits, and vegetables; drink more fluids; and get more physical activity (a daily walk may be sufficient). If constipation persists, see your doctor to make sure it is not caused by something else.

Q: Can you drink too much water?

A: Drinking too much water is seldom a concern. The body does a good job of regulating fluid intake and output. It’s safe to drink about a gallon (16 cups) a day. You probably shouldn’t exceed two gallons.

A problem called water intoxication (hyponatremia) can occur in marathon runners and other endurance athletes, people working for long hours in the heat, or even those dancing at all-night parties, usually under the influence of illegal drugs. Caused by loss of sodium from sweating during strenuous exertion, combined with overconsumption of water, water intoxication can produce nausea, fatigue, and stupor, and even coma and death. But this is not an issue if you simply drink plenty of water in the course of a normal day.

UC Berkeley Wellness Letter, February 2008