Archive 2007 2008 2009 2010

Q: Are caffeinated beverages dehydrating? Do they count towards my eight-a-day glasses of water?

A: Many people think they can’t count coffee, tea, and colas as part of fluid intake, because caffeine promotes urination briefly. But you don’t end up with a net loss of water from drinking moderate amounts of caffeinated beverages. In other words, they don’t dehydrate you.

For instance, in a study from the University of Nebraska Medical Center a decade ago, healthy adults showed the same "hydration status" (as determined from urine analysis and other tests) when they drank caffeinated colas and/or coffee as when they drank only water and/or fruit drinks. And in its 2005 report on water needs, the Institute of Medicine (IOM), which advises the government about health issues, including dietary intakes, concluded that "caffeinated beverages appear to contribute to the daily total water intake similar to that contributed by noncaffeinated beverages."

In any case, it’s a myth that you need to drink eight glasses of water a day. There’s no scientific backing for this rule. The IOM report confirmed this, too. People normally get enough fluids by drinking when they’re thirsty—though older people should drink water before they get thirsty, especially in the heat, since thirst is a less reliable indicator as we age. And other beverages besides water (including caffeinated ones), as well as foods (such as fruits and vegetables), help meet fluid needs.

Q: What causes bloodshot eyes? Should I worry about them?

A: Eyes look bloodshot when the small vessels on their surface become dilated and thus are visible. Many people notice that their eyes are red first thing on awakening. Insufficient sleep, an allergy, or overuse of contact lenses are possible causes. Bloodshot eyes during the day can be caused by some irritant, eyestrain, rubbing your eyes excessively, or anything that dries your eyes, such as high heat and low humidity.

Bloodshot eyes usually improve by themselves. Washing your face and eyelids with cold water can help, and so can cold compresses. Over-the-counter eye drops and eyewashes may help, too. Eyecups can be a source of infection, so use only the disposable kind.

Colds, flu, and hay fever can also produce bloodshot eyes, but occasionally the condition can be a sign of more serious disease or injury. Conjunctivitis, or "pinkeye," which is usually more alarming-looking than bloodshot eyes, is an infection that can produce very red, irritated eyes, as well as itching and a discharge. If you think you have an eye infection, if your eyes don’t clear up, or if you have eye pain or changes in vision, you should seek medical advice.

Q: When you discussed poultry safety last month, why didn’t you mention washing the raw birds?

A: The USDA advises cooks not to rinse raw poultry (and meats), since rinsing can easily spread bacteria from the poultry to the sink, countertop, utensils, and other foods. Raw poultry often contains Salmonella or Campylobacter bacteria, leading causes of food poisoning. Proper cooking destroys the bacteria.

If you find the idea of cooking (and eating) unwashed poultry unappealing, go ahead and wash it. But minimize the risk of cross-contamination. After handling raw poultry, scrub your hands thoroughly with warm water and soap. Plain soap is fine, you don’t need antibacterial brands. Wash the sink, faucets, and countertops—anywhere the juices might have splattered. Sponges used for the poultry juices can be washed in the dishwasher, soaked in diluted bleach, or microwaved for two minutes. Better yet, use paper towels for cleanup.

Q: A routine CT scan of my coronary arteries revealed extensive calcium deposits. My doctor said these can trigger a heart attack. Could this have been caused by calcium I’ve consumed? Is there any way to remove the calcium?

A: There’s no reason to think the calcium you get from food or supplements increases calcium deposits (calcification) in plaque in coronary arteries and other blood vessels.

Coronary calcification has been linked to higher cardiovascular risk. Calcium is deposited in plaque as part of the atherosclerosis process, and as such is caused largely by chronic inflammation in the blood vessel wall, not by high levels of calcium in the blood. In any case, the body is very good at regulating calcium in the blood (except in people with certain metabolic and/or kidney conditions). Calcium in the blood does not simply build up in artery walls. Nearly all studies have found that calcium supplements do not affect arterial calcification or the risk of heart disease.

It’s not known what steps can reduce arterial calcification—other than the advice for reducing atherosclerosis, such as intensive dietary changes and weight loss. Some studies suggest that cholesterol-lowering statins may slow the progression of calcification, but drug therapies have yielded inconsistent results overall. A study from Tufts University in 2009 found that high doses of vitamin K may help slow calcification. But it’s too soon to recommend K supplements for this purpose. If you’re on an anticoagulant such as warfarin, you should avoid them.

By the way, we don’t recommend routine screening of healthy people for calcification, which is done with special CT scans, even though some cardiologists promote it for those at higher risk for heart disease. Such screening is still being debated because it’s unclear how much information it provides for predicting heart disease beyond an evaluation of standard risk factors.

UC Berkeley Wellness Letter, April 2010