(FORTUNE Magazine) – What's the latest on cell phones and brain tumors?

The theory is that the antenna exposes the brain to radio-frequency energy, which may lead to brain tumors. Three recent studies found no increase in risk, so talk away.

Is soy all it's cracked up to be?

Yes. Soy is the only vegetable food that's a complete protein--it contains all the essential amino acids. It lowers cholesterol and may reduce the risk of heart disease and some cancers. Much of this is due to isoflavones--weak, plant-based estrogenlike compounds found in soy that appear not to have the drawbacks of estrogen.

Does aspirin really prevent heart disease?

The final event that causes a heart attack is often a blood clot in an artery narrowed from plaque buildup. Aspirin thins the blood, making it less likely to clot. It also may help prevent a stroke in people with a history of stroke or transient ischemic attack (ministroke), and it appears to prevent colon polyps from recurring. On the downside, aspirin increases the likelihood of a type of stroke due to bleeding in the brain, and it can irritate the stomach and cause bleeding in the intestinal tract. In general, people with a history of coronary heart disease or stroke should consider a daily aspirin unless they have a history of intestinal bleeding or uncontrolled hypertension, or are taking blood thinners such as warfarin. For people without a history of coronary heart disease, the benefits of aspirin increase with age. A baby aspirin is probably all you need.

Should women take testosterone?

Both men and women make testosterone. Women who've had their ovaries removed or who have pituitary problems may have low levels (and levels fall by one-third after menopause). Testosterone replacement strengthens bones and muscle and may improve sex drive and mood, but we need more studies and better ways to administer it. Too much testosterone brings side effects like hair growth, acne, and a drop in HDL ("good") cholesterol. The patches currently available, designed for men, provide too high a dose for women; oral testosterone isn't available by itself; and injections require that blood levels be monitored carefully.

Butter or margarine?

Because butter is high in saturated fat, which raises blood cholesterol, we used to think margarine was better--but we now know it, too, raises LDL ("bad") cholesterol and lowers HDL cholesterol. There's another option: two new margarines, Benecol and Take Control, both of which are made from phytosterols (cholesterollike substances in plants). These margarines can reduce LDL levels 10% to 15%, even if you're already taking cholesterol-lowering medication. Olive oil and canola oil are other heart-healthy options.

Is there anything to do about hair loss?

Two drugs may help slow it down and even regrow hair you've lost: Minoxidil (Rogaine) is applied to the scalp; finasteride (Propecia) is taken orally. The drugs aren't effective if you're completely bald, and not everyone responds (though they have worked for men and women). The best candidates are those with thinning hair and small hairs present. It takes six to 12 months to see the maximum effect. Stop the medication, though, and new hair growth is lost.

FOR MORE INFORMATION ON THIS TOPIC: Go to mayoclinic.com. Mayo Clinic offers Executive Health programs at facilities in Jacksonville, Fla.; Rochester, Minn.; and Scottsdale, Ariz.