Other articles by Andrew Weil:

Ask Dr. Weil : Growing method doesn't determine nutrition value Ask Dr. Weil : Monitor toxins that body burden tests measure Ask Dr. Weil : Nasal-spray flu vaccine is safe for kids over 2 Supersweet, natural stevia appears to be safe Olive oil adulteration is a tough problem to solve Registered dietitians and certified nutritionists No reason to buy supplemental bovine colostrum No clear evidence on cell phone's long-term risks Soy eaten in whole, unrefined forms is preferable Chemical used for sterilizing almonds a concern

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Q I cannot understand how experts can have such opposing views concerning the roles of testosterone and estrogen in prostate cancer. What is your opinion on the issue of male hormone replacement?

A Like breast cancer, prostate cancer is a hormonally driven disease. The main hormone of concern here is testosterone, which is responsible for male secondary sex characteristics as well as some of the sex drive in both men and women. Because most prostate cancers need testosterone to grow, one approach to treatment is to suppress its production with drugs. This therapy used to be reserved for advanced or recurrent prostate cancer, but it is now sometimes recommended for men with early-stage disease.

It's important to know that not all prostate cancers are testosterone-dependent (just as not all breast cancers are estrogen-dependent). Also, as prostate tumors grow, cells composing them may lose their sensitivity to testosterone.

The drugs that shut down testosterone production are called LHRH (luteinizing-hormone-releasing-hormone) agonists. Estrogen can sometimes help, too, but because its use has been linked to blood clots and breast enlargement and tenderness, the LHRH agonists are now preferred (although estrogen may still be recommended when testosterone-based therapies no longer work). At best, hormone therapy shrinks prostate tumors by 85 to 90 percent but doesn't cure the disease; the effects last only 24 to 36 months.

Because prostate cancer is hormonally dependent, you may be able to lower your risk of the disease by avoiding commercially raised beef containing hormones. Diets high in red meat and saturated fat have been correlated with an increased risk for prostate cancer.

High calcium intake from dairy foods has also been implicated (calcium might use up vitamin D, which is protective against cancer in the prostate). For this reason I recommend keeping your daily intake of calcium below 700 mg from all sources and taking 1,000 IU a day of vitamin D3.

A diet that includes soy foods (particularly from an early age) also appears to be protective. The protective phytoestrogens in soy foods can lower the risks of both prostate and breast cancer. Increase your fiber intake, as well: Fiber helps your body eliminate hormones such as testosterone. Freshly ground flaxseeds are a good source of fiber. Sprinkle 1 to 2 tablespoons daily on cereal, salad or cooked vegetables.

As for testosterone replacement, I'm concerned about its inappropriate use. Taking sex hormones of any kind can increase the risk of hormonally sensitive cancers. In my view, testosterone replacement should be considered only when blood tests indicate a deficiency in the natural production of this hormone that might be contributing to some medical problem.

QWhat are your thoughts about herbal contraceptives — i.e., Queen Anne's lace or wild yam — as short-term and long-term birth control?

AI wouldn't rely on either. My colleague Tieraona Low Dog, M.D., cautions that wild yam, used in a number of hormone-containing medicines, is not an herbal contraceptive and definitely will not prevent pregnancy. Queen Anne's lace once was used as a sort of "morning-after" treatment; some limited evidence suggests that it might work — emphasis on might.

There are several non-pharmacological approaches to birth control. Of these, your best bets are the "barrier" methods. Used consistently, diaphragms are 84 percent effective when coupled with a spermicidal cream; used consistently and correctly, condoms are 97 percent effective — and also reduce the risk of sexually transmitted diseases.

Combining two of the natural methods described below can also work. For example, the cervical mucus method plus the temperature method has a 98 percent success rate.

● Cervical mucus: This vaginal discharge reflects estrogen levels at various points in the menstrual cycle. You probably won't notice any just after menstruation. Later, mucus becomes cloudy and sticky. When it resembles raw egg white, ovulation is near. Avoid intercourse until four days after the mucus disappears or becomes cloudy and sticky again.

● Temperature: Here, you take your temperature with a special "basal" thermometer as soon as you wake. Normal temperature ranges from 97.2 to 97.7 degrees Fahrenheit before ovulation. Hormonal changes then boost it by 0.5 to 1.6 degrees. Avoid intercourse until your temperature returns to normal.

● Calendar method: Avoid sex during the week that you're ovulating. To calculate this accurately, track your periods for a year. Then subtract 18 from the number of days of your shortest cycle. This is when you are likely to be fertile and should avoid sex. To calculate when you can resume, subtract 10 from the number of days in your shortest cycle. Used alone, the calendar method is 75 percent successful.

● Withdrawal: Withdrawal of the penis from the vagina before ejaculation is the least reliable method, with a success rate of only 60 to 80 percent.