Q. Why do my doctors tell me not to drink green tea 24 hours before a blood test or three days before surgery? How is it harmful? – Vera, North Bay, Ontario
A. Some of the very properties that make green tea so great for you have the potential to mess with your blood tests and operations. Green tea can prevent blood clotting, much like aspirin does (which is why you need to tell your doctor if you drink it).
The real reason not to drink it before blood tests is the same reason docs don’t want you to eat anything before blood tests: Like food, the green brew can alter your blood sugar levels in ways that could throw off the results of a diabetes test. If you drink green tea with sugar in it, that also could elevate your triglyceride levels. Finally, your docs may consider green tea an herbal supplement, and many physicians want you to stop all herbs and supplements before tests or surgery, because they may contain contaminants that could interfere with testing or medications. (Technically, green tea is an herb, but so are regular tea and coffee, because they’re also plant-based.)
Q. My fiance has polycystic kidney disease, and his kidneys function at only 23 percent. I’ve heard there is a diet that will help him, but I haven’t been able to find any information on it. Do you know of such a thing? – Darlene, Beaumont, Texas
A. There is some evidence that a low-protein diet may slow the progression of kidney disease by taking some of the workload off these organs. When your body processes a steak, for example, it produces a waste product called urea, which healthy kidneys filter out of the body. Kidneys that aren’t working very well have to work hard to get rid of it, and they don’t always do such a great job: Urea often builds up in the bloodstream and causes fatigue and loss of appetite. It also can build up in the kidney itself, speeding up the decline in kidney function.
For people with kidney disease, the standard recommendation is small amounts of protein, plus grains and vegetables, and in some cases, healthy fats. But for someone close to kidney failure, an extra-low-protein diet often is better. In addition, these kidney-sparing diets also limit sodium, potassium and phosphorous, and can require supplements of essential amino acids that normally would come from protein-containing foods.
