Have you bowed down before the great and powerful Oz? No, I’m not referring to the fictional wizard from Dorothy’s magical land. I’m talking about mass-marketed medical guru and Oprah protégé, Dr. Oz. And while he may be powerful, the scientific community is not convinced that his recommendations are all that great.

On paper, Dr. Mehmet Oz has all the qualifications of a pre-eminent medical expert. He holds degrees from both Harvard and University of Pennsylvania, has authored numerous research publications, and is currently a professor and the vice-chair of surgery at Columbia University College of Physicians and Surgeons. By all accounts, Oz is both an exceptionally bright and charismatic man.

Yet, it’s these same qualities that have incited the ire of so many physicians and scientists. Given his education and influence, there’s no excuse for the unsubstantiated claims and sensational language that is so pervasive on his show. I’m not sure whether it’s willful blindness or calculated deception that causes him to disregard rigorous scientific standards. But the result is that many of his recommendations are akin to the cure-all elixirs peddled by door-to-door salesmen in the patent medicine era of the late 1800s.

A quick jaunt into the science blogosphere reveals a litany of unsubstantiated claims including: the effects of low-calorie sweeteners on appetite; red palm oil and raspberry ketones as effective weight-loss supplements; excessive coffee consumption to prevent diabetes; fear mongering about arsenic levels in apple juice; and even lending credibility to homeopathy. These posts are being written by a growing number of concerned scientists. Oz often supports these claims by hosting “experts,” such as quack physician and anti-vaccine proponent, Joseph Mercola, describing him as a “pioneer in alternative medicine” and “a man your doctor doesn’t want you to know.”

In fairness, Oz does tout the benefits of balanced nutrition and regular exercise. But it would be hard to fill five hours a week with such a common-sense message. The idea of cutting back sodium and simple sugars is, admittedly, less seductive. And as consumers we are very open to being seduced, and more than happy to pay for it. In 2009, the US supplement industry was estimated at 27 billion according to Consumer Reports. A recent New York Times article describes dangers posed by excessive vitamin and supplement consumption; still, more than 50% of adults taking one or more dietary supplement on a regular basis.

But the ultimate cost may be much more than monetary. As a scientist, my greatest concern with Oz’s advice is his sensationalized rhetoric. Packaging medical advice into “quick fixes” and “miracle cures” undermines evidence-based medicine. It encourages individuals to seek out alternative therapies in place of necessary medical care from qualified physicians. And at its worst, lends credibility to the use of unsafe supplements with dubious regulation.

So let’s imagine that you’re not a PhD biochemist or medical doctor. Nutritional reports in the media are in constant flux; even well qualified individuals can provide unreliable information. You may rightly question: How do I know which claims to trust? Where can I get reliable scientific information?

The following is a practical guide in which I highlight some tools at your disposal to investigate media claims about health and nutrition. My goal is not to train a legion of armchair doctors. Rather, I hope to encourage readers to question the health claims they see in the media, and to seek the advice of qualified medical professionals where those claims appear to be unsupported.


A CASE STUDY: Debunking Garcinia Cambogia weight-loss supplement

On the following segment of the Dr. Oz Show, Oz promotes the health benefits of a weight-loss supplement, Garcinia Cambogia. Online sales of the supplement skyrocketed after the segment aired in the fall of 2012. Companies that manufacture the supplement have plastered Oz’s picture all over their advertisements.




Perhaps the sleazy, infomercial-esque tone of the opening 30 seconds has already set off a few alarm bells. Oz introduces Garcinia as the “newest, fastest fat-buster” before asking, “How can I burn fat without spending every waking moment exercising and dieting?”

When we cut through the hyperbolic language, we find the following:

Major claims: Garcinia cambogia extract increases weight loss by 2-3 times, compared to diet and exercise alone. Oz also claims, “It could be the magic ingredient that lets you lose weight without diet and exercise.”

Suggested mechanisms:

1)      Blocks the synthesis of new fat in your liver

2)      Suppresses your appetite by increasing serotonin levels

Evidence given:

Very little.  Several times, both Oz and his guest, internist Dr. Julie Chen, allude to a scientific basis for their claims. Oz mentions “revolutionary new research” and Chen indicates that results have been “seen in studies.” But neither gives any indication about the size of the study, whether they were placebo-controlled, whether the participants were followed over a long period of time, and there is little mention of safety, or amounts of weight lost.

Instead, they offer as proof, a ridiculous demonstration that distills the body’s complex system of fat metabolism to water being redirected from one balloon to another. Oz then moves to his giant screen to explain, in an elaborate 30-second info-graphic, how this product affects your nervous system and, therefore, your mood and appetite.

By now, that seed of suspicion should be growing! If this product is strong enough to significantly alter two of your body’s fundamental processes, fat metabolism and neural signaling, maybe its use should be directed and overseen by a qualified physician? Maybe there is potential for serious adverse effects? Or maybe it just doesn’t work…






When considering the source, be it a person or organization, think of the two D’s: dollars and degrees.

Follow the money. Does the person recommending this product seek to benefit financially, either directly or indirectly, from its use? During the segment, Oz mentions that he is not endorsing a specific brand. But while he is not selling Garcinia directly, he is selling the idea that “the holy grail of weight loss” exists, and you can “hear about it here first.” This is what keeps his viewers returning and his books flying off the shelves.

Doctor knows best? Are the promoters of this product qualified to do so? Have they graduated from an accredited medical college or PhD program? Do other members of their field support their position?

By all accounts, Oz does possess the necessary qualifications to act as a medical expert. And this is why so many scientists have felt compelled to speak out against his recommendations. He should, and likely does, know better. As to whether or not the consensus supports his position, we’ll address that when we dive into the research.

In other cases, keep in mind that all doctors are not created equal. Be wary of those that claim the title, but who have attended online, non-accredited programs. And look for research that the author has published in peer-reviewed research journals.



Using an online search engine is often a good place to start when investigating a claim. This can give you an indication of whether or not the claim has been supported or disputed by others. The best resources will provide you with links to the original research papers that support or refute the claim. The resource should also identify the author, his or her qualifications, and whether or not they have a vested interest in the product. University or government websites, and non-profit disease advocacy groups are often reliable sources of information.

In this case, followed by a seemingly never-ending cascade of advertisements, a Google search for “Garcinia Cambogia” returns this Wikipedia page. Here, they indicate potential liver toxicity following long-term exposure, and no efficacy as seen in a placebo-controlled trial in the Journal of the America Medical Association. Not conclusive, but certainly an indication that the claims have been disputed. So now we move on to the good stuff as we are prompted to dive a little deeper into the research.



This is the most important and, unfortunately, for many the most opaque step in the investigation of any health claim. But there are some resources at your disposal.

Your best toolbox is to be aware of research methods and whether or not the study has clinical relevance. There are some very engaging and non-technical books on this topic, such as Bad Science, by UK physician Ben Goldacre. I’ve summarized a few of the key points:

Basic research does not equal clinical relevance. Otherwise put, a chemical that has an effect in a petri dish very often does not trigger the same reaction in a person. It’s a good place to start but, remember, our bodies have many complex levels of regulation. The gold standard of efficacy is a well-designed clinical trial.

 - What is a well-designed clinical trial? Another hefty question. Look for large numbers of study participants, followed over a long period of time, randomized and double-blind, and compared to either placebo or the current standard of care. It should be published in a peer-reviewed research journal. Now, you are on the right track!

 - Clinical trials will evaluate both safety and efficacy. Safety is the first priority. The severity of side-effects that we are willing to tolerate will depend on the illness being treated. For example, the FDA will approve cancer drugs with severe negative side-effects, if they can prolong someone’s life. With a weight-loss supplement, the tolerated side-effects will be close to zero.

- Studies should be reproducible. One is rarely enough. Look for a consensus among several independent studies.

To expand on this last point, look for a meta-analysis – a systematic review that combines data from many small trials, eliminating those with faulty methods. These give a better picture of most up-to-date understanding of a given field. The Cochrane Collaboration, which publishes Cochrane Reviews, is a reputable source of information.

With this information in hand, a quick search for “Meta-analysis of weight loss supplement Garcinia Cambogia” gives us two papers that review all available research, clearly outline their methods, and come to the same conclusion: Garcinia Cambogia has no significant effect on weight loss. If interested, you can read more in The American Journal of Clinical Nutrition and the Journal of Obesity.


Don’t be blinded by science. This model of investigation can be applied to many diet and health trends. Armed with the right questions, you may find that just like the wizard’s spells, many of the promised “miracle foods” and “fat-busters” are little more than smoke and mirrors – or, in our own Oz’s case, white coats and fancy info-graphics.


Act: If you’d like help investigating a claim, a great resource is the Ask for evidence campaign initiated by international science advocacy group Sense about science.


Blogging beachside at the Red Sea in Egypt. Amazing (concerning?) that I can rant away in this setting.

Blogging beachside at the Red Sea in Egypt. Amazing (concerning?) that I can rant away in this setting.

Erin May is a PhD Candidate in Chemical Biology at Harvard University.