If you made a list of the most famous doctors in America, Dr. Oz would surely be at the top. A surgeon who rose to fame after appearances on the Oprah Winfrey Show, Dr. Oz now hosts his own television show focused on health and well-being. Never one to confine himself to traditional medical practices, Dr. Oz is fond of touting the latest vitamins and nutritional supplements, even when they haven’t been fully scientifically vetted. Recently, this has landed him in some hot water with Congress.
At congressional hearings in 2014, lawmakers pointedly questioned Dr. Oz about claims he’s made about a variety of health and weight-loss supplements (1). Politicians like Senator Claire McCaskill of Missouri pointed out the wide gap between the claims Dr. Oz has made on his show about a variety of supplements, ( see: forskolin) and the actual scientific evidence that backs them.
What does the scientific literature say about some of the supplements that Dr. Oz has promoted on his show over the years?
Green Coffee Bean Extract
One of the supplements that featured prominently in the congressional hearings is green coffee bean extract. As reported in The Atlantic (2), Dr. Oz called green coffee bean extract a “miracle pill” which can “burn fat fast for anyone who wants to lose weight.”
There is indeed some science on green coffee bean extract—a 2006 study found that the supplement, when provided in high doses, reduced body fat slightly in lab mice (3), and a 2012 experiment by researchers at the University of Scranton found that humans taking green coffee bean extract dropped their body fat percentage by an impressive four points (4).
However, the study in mice was conducted and funded by employees of a company in Japan that sells green coffee bean extract, and the University of Scranton researchers retracted their own paper after the Federal Trade Commission filed a complaint saying the study’s design was “hopelessly flawed.” A retraction in the scientific community essentially invalidates the study. It doesn’t mean the study found the wrong answer to the question of whether green coffee bean extract promotes weight loss, but it does mean that the study’s design was so poor as to render its results useless (5).
Similar conflict-of-interest problems plague some of the science behind raspberry ketone pills, another supplement praised on the Dr. Oz show. In a 2005 scientific paper published in the journal Life Sciences, Japanese researchers fed two groups of lab mice a high-fat diet in an effort to induce weight gain. One of these groups of mice had raspberry ketone mixed into its food, and the researchers found that these mice did not gain weight like the control group did, despite their high-fat diet. This sounds promising, but most of the paper’s authors weren’t university-affiliated scientists; they were employees at a company called Kanebo, which markets a raspberry ketone weight-loss pill (6).
A later study by Kyoung Sik Park at the Korea Food & Drug Administration appears to be unbiased. By putting specially-bred fat cells onto a Petri dish and studying the changes in their metabolism when exposed to raspberry ketone, Park was able to determine that the raspberry ketone solution altered fat metabolism in several beneficial ways (7). This could indicate that it’s biologically active in a way that’s useful for people looking to lose weight, but cells under a microscope are still a long ways from a placebo-controlled, double-blind clinical trial in humans.
An herbal extract of the coleus forskohlii plant, forskolin supplements are another Dr. Oz favorite. Research indicates that it might have some influence on body composition. A 2005 paper by researchers at Baylor University followed 19 women who took either a forskolin supplement or a placebo twice daily for 12 weeks (8). Though neither group actually lost weight, the researchers noted that the women taking forskolin tended to gain less weight, though the difference was not statistically significant.
Similar results were reported in a 2005 study by researchers at the University of Kansas who studied 30 overweight men (9). Forskolin, taken twice daily for twelve weeks, reduced fat mass compared to a placebo, but did not actually result in weight loss: men in both groups gained muscle mass during the course of the study—though this is a good thing, as this forskolin blogger points out.
Though these studies indicate that there might be some benefits to taking a forskolin supplement, it’s important to note that these studies used very few subjects and had relatively modest results. Additionally, both were funded by the Sabinsa Corporation, which sells a forskolin-based weight loss supplement.
These conflicts of interested are problematic because there’s an incentive for researchers to tweak the design of experiments so that they’re more likely to find a result that’s pleasing to the company providing the funding. This doesn’t mean they’re invalidated, just that they need to be viewed with more skepticism than a truly independent study.
Maybe not a miracle, but hope nonetheless?
Defending his claims before Senator McCaskill’s Subcommittee on Consumer Protection, Dr. Oz explained that his approach is one of a motivator and cheerleader, giving people the hope they need to start living healthier lives and losing weight. He backpedaled a bit from the bold claims made on his show, but still defended many of these supplements as safe and worth a try.
In the end, no punishments were leveled against Dr. Oz, and he left with his head held high. Since then, there’s been some movement to place further restrictions on dietary supplement advertising claims, but no concrete results yet. Illinois Senator Dick Durbin and Connecticut Senator Richard Blumenthal have introduced legislation that would require supplement manufacturers to register their supplements with the Food and Drug Administration, but no votes were ever held (10).
In light of all this, how should you decide if a supplement is right for you? The best approach is to do your homework first. Realize that dietary supplement manufacturers operate under fairly loose regulations, so they can make bold claims in their marketing materials without a lot of evidence to back them up. Read up on a supplement from trusted sources so you can decide whether it’s worth a try.