Out of all adverse event (AE) reports that were submitted to the FDA over a time period of 2.5 years, only 203 out of 41,121 (0.48%) were serious adverse events (SAEs). That's the findings of a study published in theJournal of Dietary Supplements that looked at one company—Supplement Safety Solutions, which works with dietary supplement marketers to review and report SAEs to the FDA.

The study, titled “Serious Adverse Events Reported with Dietary Supplement Use in the United States: A 2.5 Year Experience” by Stephen M. Schmitz,et al., begins by noting that 52% of U.S. adults report use of dietary supplements: 75% of those adults take vitamins/minerals, 38% take specialty supplements, 29% take herbals/botanicals, 22% take sports nutrition supplements and 15% take weight management supplements.

The study then goes in-depth regarding the principles of “nutravigilance,” which is defined as “the science and activities relating to the detection, assessment, understanding and prevention of adverse effects related to the use of a food, dietary supplement, or medical food.” Douglas McKay, N.D., senior VP of scientific and regulatory affairs at the Council for Responsible Nutrition (CRN) and co-author of the study, toldWholeFoodsthat this system helps make it unique. “The whole idea is interesting. This isn’t a generalized statement—dietary supplements are safe, or aren’t safe—it allows us to look at what AEs are caused by what, what’s associated with what.”

The study found that a total of 532 unique symptoms were reported among the 203 SAEs, with dizziness, syncope, nausea, vomiting, and dehydration among the most common. Weight-loss agents, both thermogenic and nonthermogenic, were the most frequent types of dietary supplements reported with SAEs, followed by glucose control/insulin management agents in a distant second and digestive aids in a still more distant third. This too is important, Dr. McKay says, and also why making generalized statements about safety is useless. “Multivitamins and echinacea aren’t causing AEs. It’s the more aggressively formulated products—weight-loss products, pre-workout products—that tend to have more AEs. This is useful information for formulators and producers to have, because they can use it to make safer products.”

It’s important to note that correlation does not equal causation, and that causal relationships are difficult to determine. For instance, thermogenic weight-loss supplements typically contain ingredients like green tea extract and caffeine; green tea extracts have been associated with cardiovascular side effects, and caffeine has been shown to have neurostimulant effects. Thus, the AEs reported with these supplements—dizziness, tachycardia, chest pain—have a plausible relationship. However, the researchers note in the study, this is not always the case: concomitant medications, dehydration, or preexisting conditions can confound doctors’ abilities to draw a connection between symptom and supplement.

On the other end of the spectrum, nonthermogenic weight-loss agents tended to be associated with gastrointestinal issues and cardiac issues. The researchers noted that the major components in this category, conjugated linoleic acid andGarcinia cambogia, are both generally considered safe, and are not cardiostimulatory, suggesting that at the very least, cardiac AEs associated with these supplements are not likely to be caused by them.

Dr. McKay said on the topic, “This has been a concern since the law requiring AEs to be reported was passed: people might take AEs as being causal, when post-market research like this can’t really determine causal relationships. There’s no way to determine a direct link between a single product and a health issue. This data serves as a signal to the FDA, when there’s something that needs to be examined.” In the study, the researchers noted that not all information was always available—and that includes things like general health and other medications, both of which could be theactualcause.

So what’s the best way to take in this study? As ground-breaking data collection within the dietary supplements industry. “How many dietary supplements are out there?” Dr. McKay asks. “We don’t even know. It’s hard to refute news that slams the industry, because we don’t have the data to do so. We’re hoping that this study will encourage other data-collecting companies to publish their data, so we can get a clearer picture of the industry. We’re hoping that more people will use theSupplement OWL, and so on.” This study is hypothesis-generating, he says, and we need more proof.