Oprah says things like this without irony. But really, how could it not go to her head, even a little? Her most ardent fans regard her as an oracle. If she mentions the title of a book, it goes to No. 1. If she says she uses a particular wrinkle cream, it sells out. At Oprah's retail store in Chicago, women can purchase used shoes and outfits that she wore on the show. Her viewers follow her guidance because they like and admire her, sure. But also because they believe that Oprah, with her billions and her Rolodex of experts, doesn't have to settle for second best. If she says something is good, it must be.

This is where things get tricky. Because the truth is, some of what Oprah promotes isn't good, and a lot of the advice her guests dispense on the show is just bad. The Suzanne Somers episode wasn't an oddball occurrence. This kind of thing happens again and again on Oprah. Some of the many experts who cross her stage offer interesting and useful information (props to you, Dr. Oz). Others gush nonsense. Oprah, who holds up her guests as prophets, can't seem to tell the difference. She has the power to summon the most learned authorities on any subject; who would refuse her? Instead, all too often Oprah winds up putting herself and her trusting audience in the hands of celebrity authors and pop-science artists pitching wonder cures and miracle treatments that are questionable or flat-out wrong, and sometimes dangerous.

Oprah would probably not agree with this assessment. She declined to be interviewed for this article, but in a statement she said, "The guests we feature often share their first-person stories in an effort to inform the audience and put a human face on topics relevant to them. I've been saying for years that people are responsible for their actions and their own well-being. I believe my viewers understand the medical information presented on the show is just that—information—not an endorsement or prescription. Rather, my intention is for our viewers to take the information and engage in a dialogue with their medical practitioners about what may be right for them."

The first-person story that, as Oprah says, puts "a human face on topics" is an important part of the show's success. Perhaps Oprah's most attractive quality, and one that sets her apart from other daytime hosts, is that she abhors the celebration of victimhood. She succeeded despite a childhood of abuse, and her own experience left her with very little tolerance for people who indulge in self-pity or blame cruel fate for their troubles. She often features regular people or, even better, celebrities, who have met challenges in their lives.

In 2007, Oprah invited Jenny McCarthy, the Playboy model and actress, to describe her struggle to find help for her young son. When he was 2½, Evan suffered a series of seizures. A neurologist told McCarthy he was autistic. "So what do you think triggered the autism?" Oprah asked McCarthy. "I know you have a theory."

McCarthy is certain that her son contracted autism from the measles, mumps and rubella (MMR) vaccination he received as a baby. She told Oprah that the morning he went in for his checkup, her instincts told her not to allow the doctor to give him the vaccine. "I said to the doctor, I have a very bad feeling about this shot. This is the autism shot, isn't it? And he said no, that is ridiculous; it is a mother's desperate attempt to blame something on autism. And he swore at me." The nurse gave Evan the shot. "And not soon thereafter," McCarthy said, "boom, soul gone from his eyes."

McCarthy is now the most prominent voice in a small but vocal movement of parents with autistic children who are demanding action from the government. They believe that chemicals once used to preserve vaccines, combined with the increase in the number of shots kids get today, have created an epidemic of autism; and that doctors, the government, the media and drug companies are hiding or ignoring the truth. McCarthy declined an interview, but in a statement she said, "I understand that vaccines are an important part of keeping us alive today. My problem is with the ingredients in some vaccines that can become toxic when introduced to children with vulnerable immune systems. I want those children to be able to delay vaccines that could cause them harm."

It is easy to see why parents like McCarthy have latched onto vaccines as the culprit. They want answers, and sadly there are few. Studies have found some genetic and environmental links that may increase the risk of autism, but its causes are still unknown. The baffling rise in the number of autism cases has loosely coincided with an increase in the number of childhood immunizations. Yet researchers have not found a link between the vaccines and autism. Here is what we do know: before vaccinations, thousands of children died or got sick each year from measles, mumps and rubella.

But back on the Oprah show, McCarthy's charges went virtually unchallenged. Oprah praised McCarthy's bravery and plugged her book, but did not invite a physician or scientist to explain to her audience the many studies that contradict the vaccines-autism link. Instead, Oprah read a brief statement from the Centers for Disease Control saying there was no science to prove a connection and that the government was continuing to study the problem. But McCarthy got the last word. "My science is named Evan, and he's at home. That's my science." Oprah might say that McCarthy was just sharing her first-person story and that Oprah wasn't endorsing her point of view. But by the end of the show, the take-away message for any mother with young kids was pretty clear: be afraid.

Oprah told viewers that McCarthy would be available to answer questions and give guidance later that day on Oprah.com. One viewer went online to ask McCarthy what she would do if she could do it all over again. "If I had another child," McCarthy answered, "I would not vaccinate." A mother wrote in to say that she had decided not to give her child the MMR vaccine because of fears of autism. McCarthy was delighted. "I'm so proud you followed your mommy instinct," she wrote. A year later, McCarthy was back on the show for an episode about "Warrior Moms," which gave her another opportunity to expand on her claims about vaccines and autism. Oprah must have liked what she heard. McCarthy became a semiregular guest on the show, and in May, Oprah announced that her production company had signed McCarthy for a talk show of her own.

McCarthy is not the only guest who has warned Oprah's viewers off vaccines. Last summer Dr. Christiane Northrup, a physician and one of Oprah's regular experts, took questions from the audience. One woman asked about the HPV vaccine, which protects women against a sexually transmitted virus that can cause cervical cancer. Northrup advised against getting the shot. "I'm a little against my own profession," she said. "My own profession feels that everyone should be vaccinated." But Northrup cautioned, "There have been some deaths from the vaccine." She suggested a different approach. "Where I'd put my money is getting everybody on a dietary program that would enhance their immunity, and then they would be able to resist that sort of thing. All right?"

It is true that of the millions of women who have received the vaccine, 32 have died in the days or weeks afterward. But in each case, the Centers for Disease Control and the Food and Drug Administration investigated the deaths and found that they were coincidental and were not related to the shot. "This is a very safe vaccine," says Susan Wood, a research professor in the School of Public Health at George Washington University and the former head of the FDA's Office of Women's Health. "Because of the power and influence that Oprah's show has, she should make an extra effort to be clear." Neither did Oprah question Northrup's assertion that women can stop the spread of a cancer-causing sexually transmitted disease by eating healthy foods. There is, Wood says dryly, "no evidence that money spent on general health promotion" will do that. Reached by phone, Northrup herself now concedes she isn't certain that anyone has died from the vaccine. And she didn't mean to leave the impression that women should avoid it. "I would say that there is a chance that they could be injured from it, but I wouldn't say not to take it."

Northrup holds a special place in Oprah's constellation of regular guests. A Dartmouth-educated ob-gyn, she stresses alternative therapies and unseen connections between the soul and the body that she believes conventional doctors overlook, but that she can see. She has written about how she has used Tarot cards to help diagnose her own illnesses. (On her Web site, she sells her own "Women's Wisdom Healing Cards.") In other words, she gets right to the center of Oprah's search for hidden mystical meanings. Oprah says she reads Northrup's menopause book "just like it's the Bible. It's the book next to my bed. I read the Bible. I read that book." (Disclosure: NEWSWEEK correspondent Pat Wingert, who worked on this article, and contributor Barbara Kantrowitz are coauthors of a book on menopause.)

Oprah turned to Northrup for advice in 2007, when, as she put it, she "blew out" her thyroid after a stressful season of work and travel. She felt sick and drained and she gained weight. She asked the doctor to come on the show to explain what was going on. "When I called her to talk about this whole thyroid issue," Oprah told the audience, "she always connects the mind, the body and the spirit."

Thyroid dysfunction, which affects millions of Americans (mostly women), occurs when the thyroid gland located in the neck produces too much or too little thyroid hormone. Too much (hyperthyroidism) and the metabolism races, sometimes causing anxiety and weight loss. Too little (hypothyroidism) and it slows, which, if severe, can lead to depression and weight gain. Many things can trigger the disease, especially autoimmune disorders.

But Northrup believes thyroid problems can also be the result of something else. As she explains in her book, "in many women, thyroid dysfunction develops because of an energy blockage in the throat region, the result of a lifetime of 'swallowing' words one is aching to say."

On the show, she told Oprah that "your body gives you signals: 'Hey, you've been putting too much stuff under the carpet ...' "

Oprah : So your body ... is only manifesting what's really going on with your spirit?

Northrup: But your intellect doesn't know it. This is the important part. It's not—you're not causing this deliberately ... It's your soul bringing it to your attention.

Oprah: Right. It's your soul trying to speak to you.

An interesting theory—but is there anyone who believes that what Oprah suffers from is an inability to express herself? She didn't make it clear on the show what form of the disease she had, or what her doctors believed brought it on. She shared with her audience that she took thyroid medication and spent a month relaxing in Hawaii, where she ate fresh foods and drank soy milk. Northrup advises that in addition to conventional thyroid medication, women should consider taking iodine supplements.

That is just what they shouldn't do, says Dr. David Cooper, a professor of endocrinology at Johns Hopkins medical school who specializes in thyroid disease. "She is mixing truth with fantasy here," he says. First, "thyroid disease has nothing to do with women being downtrodden. She makes it sound like these women brought it on themselves." Cooper agrees that thyroid patients should seek thyroid hormone treatment to bring the symptoms under control. But, he says, Oprah should have stayed clear of soy milk. "If you're hypothyroid and you're taking thyroid medication, you do not want to be taking soy. It will block your body's ability to absorb the medication."

Iodine, he says, can be even riskier. "[Northrop] says iodine deficiency is more common in women, when in reality it's not very common in women at all. This is a myth." The thyroid gland, he says, is extremely sensitive to iodine. "If you have mild hypothyroidism, taking iodine will make it worse."

"The problem is that this all has the aura of being scientific when a lot of it is wrong, or not proven or just utter hogwash," Cooper says. "No wonder it sounds very credible to the patients, and in my opinion, that's even worse. If it was all complete rubbish, people would be more likely to see it for what it really is."

All this dreary talk of measles and cancer and thyroids. Wouldn't you rather "Stop the Clock on Aging!" Hear about "The Latest Age-Defying Breakthroughs!" Get the skinny on the miracle "Lunchtime Face-Lift Which Means No Cutting and No Down Time!" These are all teaser lines Oprah has recited on her show. Oprah hasn't had plastic surgery herself, and she has aired the cautionary tales of desperate, youth-obsessed women who ruined their faces with too many procedures. Yet she seems fascinated with the subject and has been among the first to promote the newest treatments. In 2004, Oprah debuted a new "groundbreaking" procedure on the show called a thread lift. Her guest, dermatologist Karyn Grossman, called it "pretty much as close as you can get to a face-lift without actually cutting."

Oprah liked the sound of that. "Well, let's see what this is, y'all!" she told the audience. She played a video of Grossman performing the procedure on a 61-year-old woman named Sandy. Grossman poked multiple holes on each side of Sandy's face near her ears, eyes and cheekbones, then pulled through thin threads under the skin. The threads caught in her flesh, hoisting her tissue up and back. "Threads are tied off," Oprah enthused, "and a one-hour lunch-break lift."

Sandy was in the audience to show off the results. Oprah flashed the "before" picture, what appeared to be a no-makeup shot under harsh lighting. She looked like a 61-year-old woman with no makeup. Then, the big reveal. Sandy emerged under the warm studio bulbs, her face heavily pancaked with makeup. She looked like a 61-year-old woman heavily pancaked with makeup. It was difficult to tell if there was any difference. But Sandy pronounced herself pleased with the results, and the audience burst into applause.

Oprah said almost nothing about possible risks. "It is a relatively painless procedure, I'm told," she said. "Scarring is minimal, and recovery time is measured in days instead of weeks." Yet according to Plastic Surgery Practice, an industry magazine, some doctors reported that "over time, the suture tends to act like a 'cheese wire'," cutting through delicate facial tissue. Some patients who underwent another version of the procedure, which used barbed threads, experienced bunching of the skin, dimples and scars. Others complained the left and right sides of their faces no longer matched up due to "migration of the sutures." One of the most common complaints, though, was that they couldn't see any improvement at all.

The thread-lift craze, such as it was, did not last long. "You never hear anything about them now," says Dr. Alan Gold of the American Society for Aesthetic Plastic Surgery. "That procedure turned out to have major downsides and rapidly fell into disrepute."

You would not know this from watching Oprah. The New York Times noted problems with the treatment in a 2006 article specifically about the Oprah show's tendency to hype plastic surgery without mentioning the risks. But Oprah never circled back to warn her viewers that they just might want to cross it off their to-do list. Grossman says Oprah never gave her an opening to talk about the downsides, and in the moment it didn't occur to her to raise them herself. If she went on the show again, she says, she'd do things differently. "We should have said, 'This is a new procedure. It looks interesting and exciting, but we don't know everything about it yet and there may be risks that haven't come up yet'."

Oprah was also one of the first to feature a procedure called Thermage. It smooths wrinkles by using radio waves to tighten skin. The Times article noted that Oprah was one of the first to call attention to the $30,000 Thermage machines after they were released in 2003. "The show drove so much interest that our sales reps were selling machines over the phone," the president of the company told the paper. In the years since, Oprah has featured the product numerous times on her TV show and Web site and in her magazine.

In February 2004, dermatologist Brandith Irwin appeared on an episode called "Look Younger! Live Longer!" The show aired again twice over the next two years. Irwin came on the program to promote a book and to talk about cosmetic procedures. She had nothing but praise for Thermage, which was then still a relatively new treatment. "I tell my patients they'll lose about half a day, and then you go back to your normal activities the next day." Neither Oprah nor Irwin said anything about a significant downside to the procedure: it hurt, a lot. And it didn't always work. On her own Web site, Irwin acknowledges that in those early days of Thermage, "the treatments were painful without sedation (we sedated everyone in our office), and the results were inconsistent." O magazine recently ranked Thermage as a four on a pain scale of one to five. Five was "agony." There was also no mention on the show about the potential risks, which included burns and scars.

The makers of Thermage say the latest generation of machines are more effective and far less painful. And the risk of complications is very low. Stephen Fanning, the company's CEO, says Oprah certainly helped drive sales and interest. But he is uncomfortable when his product is promoted without giving people the whole picture. "I think any time you're dealing with a cosmetic device, you always have to present a balanced approach. Oprah didn't." Fanning believes Oprah should have made it clear that Thermage isn't for everyone. "Who isn't a good candidate? Someone who smokes a lot, someone who consumes a lot of alcohol, is not going to get the kind of results they want. The same can be said for someone who has spent a lot of time in the sun."

Yet Irwin says there was no time on the Oprah show to go into these kinds of details. "It was meant to stimulate interest, and then people could go find out about it from their doctor and decide what's appropriate for them. That's what the Web site and the book and office visits are for," Irwin says. "I am in sympathy with the idea of doing better medical segments," she says. "We can't do that in 15 seconds."

Right about now is when you might be asking, is there anything Oprah gets right? In fact, there is. For one, she gives excellent diet and fitness tips. Two of her longest-serving resident experts, Dr. Mehmet Oz and trainer Bob Greene, routinely offer sound, high-quality advice to Oprah and her audience on how to lose weight and improve overall health. For the most part, it is free of the usual diet-industry hype, perhaps because so many of her viewers are on to those scams by now. Oz's and Greene's philosophy amounts to: eat nutritious foods, and exercise.

Oz, fit and handsome, is particularly good at connecting with Oprah's audience. He is a cardiac surgeon at Columbia University and generally sticks to the facts. He is also a natural showman who comes onstage in surgical scrubs, as if he might be asked to perform an emergency heart transplant at any moment. He sometimes arrives carrying preserved body parts as visual aids. On one show, "Everybody Poops," Oz conducted a genuinely fascinating seminar on what comes out the other end. (It should be shaped like an S and "hit the water like a diver from Acapulco." Who knew?)

Oz isn't without his faults. He sometimes keeps quiet on the show when Oprah's out-there experts are spouting their questionable theories. There seems to be an unwritten rule that one Oprah expert may not criticize or correct another, and Oz has an interest in keeping Oprah happy. She has turned his books into mega-bestsellers, and features him on her Web site and in her magazine. Her production company is also bankrolling his own syndicated TV show, Dr. Oz, which debuts in the fall. "My role on The Oprah Winfrey Show was never to assume editorial control or in any way to debate the position that other guests might take," Oz said in a statement. "My participation on the program, much like that of any physician on television, was never intended to replace the discussion necessary between patients and their personal health-care provider."

Oprah, of course, is notoriously bad at sticking with the advice Oz and Greene dispense, especially when it comes to her weight. She laments her inability to keep off the pounds. In January she embarked on yet another attempt to trim down, which means all of Oprah's viewers are now—actually or vicariously—on a diet too. She will lose the weight, and there will be much remarking upon it. But then, in a year, or two, or three, experience teaches us that the fat will likely come back. And she will lament. And then she will do it all over again, with a whole new set of experts armed with the latest breakthrough theories on how to live our next best life and all-new, must-have books and gadgets and ointments to ease the way.

At some point, it would seem, people will stop looking to Oprah for this kind of guidance. This will never happen. Oprah's audience admires her as much for her failings as her successes. In real life, she has almost nothing in common with most of her viewers. She is an unapproachable billionaire with a private jet and homes around the country who hangs out with movie stars. She is not married and has no children. But television Oprah is a different person. She somehow manages to make herself believable as a down-to-earth everywoman. She is your girlfriend who struggles to control her weight and balance her work and personal life, just like you. When she recently related the story of how humiliated she felt when she arrived for a photo shoot to find that she couldn't fit into the clothes she was supposed to wear, she knew she had every member of the audience in her hand. Oprah's show is all about second and third and fourth chances to fix your life, and the promise that the next new thing to come along will be the one that finally works.

This perpetual search for The Answer reached its apex a couple of years ago, when Oprah led the frenzy over The Secret. The video and accompanying book were a rehash of one of the oldest of self-help truisms—"think positive"—refreshed with a dusting of "science." The secret of The Secret was something called the Law of Attraction. As Oprah put it on the show, "It says that the energy, that the thoughts and feelings that you put out into the world, both good and bad, are exactly what is always coming back to you, so you have the life that you have created." Oprah and the teachers of The Secret, as they call themselves, did not mean this metaphorically. They explained that the universe and everything in it are made of vibrating energy, and by thinking positively we can actually "attract" the positive vibrations of the universe and bend them to our will. "You're a field of energy in a larger field of energy," one of The Secret's teachers said. "And like attracts like, and that's very, very scientific."

By harnessing this powerful science, they said, we can have anything we want—happiness, love, fabulous wealth. This was so inspiring to Oprah that she devoted three shows to the product and appeared on Larry King to talk it up more. She said it encapsulated everything she believes. "I've been talking about this for years on my show," she said. "I just never called it The Secret."

On one of the Secret shows, Oprah gave an example of the scientific power of the concept. She said that once, while she was hosting an episode about a man who could blow really big soap bubbles, she was thinking to herself, "Gee, that looks fun. I would like to blow some bubbles." When she returned to her office after the show, there, on her desk, was a silver Tiffany bubble blower. "So I call my assistant," Oprah told the audience. "I say, 'Did you just run out and get me some bubbles? 'Cause I got bubbles by my desk.' And she says, 'No, the bubbles were always there. I bought you bubbles for your birthday and you didn't notice them until today'."

There are many lessons that might be drawn from this anecdote. One is that if you give Oprah a thoughtful gift, she may not bother to notice it or thank you for it. This is not the lesson Oprah took away from her story. Because the way she sees it, her assistant hadn't really given her the gift at all. She gave it to herself. Using the power of The Secret, she said, "I had called in some bubbles."

According to The Secret, however, the Law of Attraction can use the vibrations of the universe to deliver more than just bubbles. The book that Oprah urges everyone to live by teaches that all diseases can be cured with the power of thought alone: "The question frequently asked is, 'When a person has manifested a disease in the body temple … can it be turned around through the power of "right thinking"?' And the answer is absolutely, yes." The book then offers the testimonial of a woman identified as Cathy Goodman. "I was diagnosed with breast cancer. I truly believed in my heart, with my strong faith, that I was already healed. Each day I would say, 'Thank you for my healing'." Goodman watched "very funny movies" to make herself laugh. "From the time I was diagnosed to the time I healed was approximately three months. And that's without any radiation or chemotherapy."

The message got through. In March 2007, the month after the first two shows on The Secret, Oprah invited a woman named Kim Tinkham on the program. She had been diagnosed with breast cancer, and her doctors were urging surgery and chemotherapy. But Tinkham wrote Oprah to say that she had decided to forgo this treatment and instead use The Secret to cure herself. On the show, Oprah seemed genuinely alarmed that Tinkham had taken her endorsement of The Secret so seriously. "When my staff brought this letter to me, I wanted to talk to her," Oprah told the audience. "I said, get her in here, OK?" On air, Oprah urged the woman to listen to her doctors. "I don't think that you should ignore all of the advantages of medical science and try to, through your own mind now because you saw a Secret tape, heal yourself," she said. A few weeks earlier, Oprah could not say enough in praise of The Secret as the guiding philosophy of her life. Now she said that people had somehow gotten the wrong idea. "I think that part of the mistake in translation of The Secret is that it's used to now answer every question in the world. It is not the answer to all questions," she instructed. "I just wanted to say it's a tool. It is not the answer to everything." The Law of Attraction was just one law of many that guide the universe. "Although I live my life that way," Oprah said, "I think it has its flaws."

There were limits to The Secret's healing powers even for Oprah. For there she was, in the months that followed, worrying over her thyroid, ingesting bioidentical hormones and putting on pounds. The Secret warns that all illness and misfortune is caused by attracting the negative power of the universe. "You cannot 'catch' anything unless you think you can," it says. "You are also inviting illness if you are listening to people talking about their illness."

It is possible that this is what happened to Oprah. Listening to so many guests talk about their troubles dampened her energy fields. Yet it may be for the best that things didn't quite work out. What if Oprah had managed to solve all of her problems, to end her search for meaning and fulfillment and spiritual calm and a flatter, firmer stomach by summoning the very power of the universe itself? It might have been hard for her to take Suzanne Somers seriously after that.