… On special reports: a new study reveals the exact opposite of the last new study. Which should you believe?

A few years back, there you were, having more sex each week than Wilt Chamberlain and Secretariat combined. It was all good. Then several sex studies came along: Men who gained carnal knowledge at least three times a week, the studies claimed, are 20% more likely to develop prostate cancer than a priest who actually sticks to his celibacy vow. So then you're wondering: Should you ignore the reports, host orgies, and take your chances with your prostate? Should you reduce the frequency of your sexual activity and only do it, say, once a week? Or should you castrate yourself and form a boy band?

Hold the phone! A couple of recent studies draw conclusions that precisely contradict the previous studies: Five-time-a-week ejaculators in their 20s and 30s cut their prostate risk by a third, compared with the once- or twice-a-week guys.

Now your head's spinning, which makes sense, because you're trapped in some sort of special-report spin zone, with each side trying to sell you findings that conflict with someone else's (the only upside being that Bill O'Reilly isn't moderating). How do you know what to believe? And it isn't just about doing the nasty--recent years have seen the same kind of conflicting health reports regarding everything from beef to eggs, from aspirin to marijuana (not including the reports that explore what happens when you sprinkle aspirin on your eggs).

Frequently, new research findings are so contradictory that they could drive a man to drink--which is either really good or really bad for you, depending on the study you read. Even scientists have trouble distinguishing the real deal from findings that are trivial, biased, or just plain crap. "Science requires patience," explains Gregory Burke, M.D., a professor of public-health sciences at Wake Forest University Baptist Medical Center in Winston-Salem, N.C. "It takes time--often years--to sort out contradictory findings. But when it comes to medical information, Americans are impatient."

Adds biostatistician Christopher Portier, Ph.D., director of the Environmental Toxicology Program of the National Institute of Environmental Health Sciences: "The public is more scientifically astute than it was 20 years ago. But people want certainty. In science, the only constant is uncertainty."

Yeah, the world's uncertain. But if you know some basics about evaluating research, you can have a better idea what to believe--and what to feed into your office paper shredder. We analyzed a few prime, current controversies to teach you how.

SO? CAN HAVING SEX GIVE YOU CANCER?

Not if you look critically at the data. While several studies have linked having sex to prostate cancer (the largest coming from the University of Iowa), they were done by the "retrospective" or "case control" method. The researchers asked people with cancer--the "cases"--how many times a week they ejaculated, then surveyed similar people who were cancer-free--the "controls." The advantage of retrospective/case-control studies, Portier explains, is that they can be done relatively quickly and inexpensively. "The problem is they depend on memory, which is notoriously unreliable." Think about it: A researcher asks you how many times you got off from, say, 1996 to 1999. Wanna base a whole study on collective memory? Even a small lapse in recollection can skew the results.

The more reliable type of study is "prospective," where researchers follow subjects' lives for many years. Prospective studies take more time and money, Portier explains, but are much less likely to involve faulty memories. The trial that reported having sex lowers prostate-cancer risk by a third was conducted by National Cancer Institute (NCI) researchers who surveyed nearly 30,000 men every two years for a total of eight years.

So what explains the studies showing that sex increases prostate-cancer risk? Guilt by association, explains clinical nutritionist Jeannie Moloo, Ph.D., R.D., and a spokesperson for the American Dietetic Association. Just because two things are associated--sex and prostate cancer--doesn't necessarily mean one causes the other. In studies linking the two, sexual frequency was also connected to something else: sexually transmitted diseases (STDs). Many studies show that STDs increase risk of prostate cancer. So it's the STDs--not the sex, per se--that increase prostate-cancer risk.

Now, prostate cancer may not be high on your list of immediate worries, but it just might improve your luck. Try out this line: "Hey, sweetheart--want to help me prevent prostate cancer?"

IS COFFEE BAD?

Sure, coffee gets us going. But into an early coffin? That's what you'd think if you bought into all the research. But some of the reports on the evils of java just might be jive.

Cups o' joe have been linked to three important risk factors for heart disease: (1) Researchers at the Oklahoma City VA Medical Center recently joined a chorus of previous studies showing that coffee raises blood pressure. (2) Swedish researchers recently found that filtered coffee--the kind most Americans drink--raises cholesterol. And (3) Danish researchers have discovered that drinking coffee raises levels of homocysteine, an amino acid in blood. Hmmm. Seems like coffee might be durned near the most dangerous substance since cyanide.