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Answer: As health care professionals, we are supposed to be able to answer the question, "Should I be taking this supplement?" The only way we can respond with certainty is to examine the scientific evidence. However, all evidence is not equal. Rats and mice are not people. Results from a petri dish are not appropriate. Clinicians must consider only studies done with humans.
The gold standard is a double blind randomized control trial (RCT), which involves a substantial number of subjects and multiple trials. The next best are RCTs with a limited number of subjects and trials. There are also nonrandomized trials or even observational studies that provide a basis for designing RCTs. However, without a control group, you can't be sure what caused the results.
Sometimes, when little evidence is available, clinical decisions are based on consensus judgments, but testimonials should never be a basis for use of a particular supplement. Discourage the notion that, "If it works for the person in the advertisement, it will work for me. What do I have to lose?"
Our bottom line comes from the Red Flag Campaign of the Federal Trade Commission (FTC): "If it is too good to be true, it probably isn't."1
As an example, chitosan, a major component of a number of dietary supplements, is sold to "help you lose a substantial amount of weight." Let's examine the evidence. A number of studies show that chitosan fed in large quantities (up to 15% of the diet) has fat-binding properties that increase fat excretion in rats and mice. An infomercial on the QVC shopping network showed chitosan combined in a beaker with a buffer and fat.
The buffer's composition was supposed to represent what happens in the stomach, but no further information on its makeup was given. The clumping of the fat/chitosan mixture was presented as evidence that chitosan prevents dietary fat from being absorbed in the intestine. This dubious demonstration reinforces our commitment to the idea that supplements should be tested in people, not in beakers.
We have published research on three brands of chitosan.2–4 We measured fat in the feces of men and women taking chitosan as directed. Each subject acted as his or her own control. If chitosan actually blocked the absorption of fat, we would have expected to find a substantial amount of fat in the feces. In men, fecal fat excretion increased by 1.8 g daily. This is the equivalent of 16.2 calories (1 g of fat = 9 calories/g). It would take about 216 days for men to lose 0.45 kg (1 lb) of fat by using chitosan.
In women, there was no increase in fecal fat. We concluded that chitosan did not prevent the absorption of substantial amounts of fat, and therefore taking the supplement could not result in substantial weight loss.
In March 2004, the FTC charged QVC with making deceptive claims. The
complaint alleged that QVC violated a 2000 FTC order requiring the company to
substantiate claims with scientific evidence. QVC violated that order, the FTC
alleged, by making false claims that the advertised chitosan product prevented
absorption of dietary fat and caused "substantial weight loss, for
example, 50, 60, 100 pounds or more."
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| Corrections In the article "New Blood Glucose Value, Recalibrated A1C Standard Unveiled" (DOC News, August 2007, page 6), we reported that the average glucose reading would be given in ml/dl, which is not correct. The reading will be given in mg/dl. In addition, the article mistakenly said the National Glycohemoglobin Standardization Program (NGSP) is based at Washington University in St. Louis. The NGSP is actually based at the University of Missouri-Columbia.
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References
2. Gades MD, Stern JS: Chitosan supplementation does not affect fat absorption in healthy males fed a high-fat diet, a pilot study. Int J Obes Relat Metab Disord 26:119–122, 2002.[Medline]
3. Gades MD, Stern JS: Chitosan supplementation and fecal fat excretion in men. Obesity Research 11: 683–688, 2003.[Medline]
4. Gades MD, Stern JS: Chitosan supplementation and fat absorption in men and women. J Am Diet Assoc 105: 72–77, 2005.[Medline]
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