Dietary supplements crowd the shelves of supermarkets, drug stores and medicine cabinets in just about every home. The federal Food & Drug Administration (FDA) regulates prescription and over-the-counter medicine, complete with laboratory and field testing. But the more than $30-billion supplement industry is largely regulated by the honor system, and not the FDA.
Davidson College biology professor Mark Barsoum and a team of 15 Davidson students made it their honor-bound responsibility to investigate the claims on the labels of herbal supplements.
Makers of these supplements, which include vitamins, hormones and herbals, claim their products promote health and prevent disease. But, the team asked, should consumers trust that what's on the label is in the pill?
Barsoum and the students participated in Davidson's Research in Science Experience (RISE), which provides opportunities for hands-on undergraduate research to students from groups historically underrepresented in science.
Their research of supplements found that many of their samples appeared as advertised, but also uncovered a few surprise ingredients in the pills, such as: rice, bamboo and even Cannabis.
"[Supplements are] a highly unregulated industry," Barsoum said, "and there is a powerful lobby in Washington fighting for supplements to remain unregulated."
The researchers aimed to identify plant species inside the pills and uncover evidence that herbal supplements do (or do not) contain what their labels promise.
They hypothesized the pills might contain ingredients other than the primary one listed on the label because previous studies have confirmed the presence of unadvertised plant matter in many supplements. With that assumption in mind, the researchers embarked on a search for a broad spectrum of plant genomes.
The group's dietary detective work began with instruction on how to isolate and clone genes from raw plant matter or environmental samples.
Anna Jones '20 and Teyonn Ennis '20 explained the methods involved in amplifying DNA from their herbal supplement, Astragalus root, which claims to support immune health.
"We get a feel for all different steps: DNA extraction, setting up for PCR (Polymerase Chain Reaction), PCR reaction recipe, how to make agarose gel, how to run gel electrophoresis," Jones said.
After extracting the DNA of the herbal supplement, students conducted a PCR, which amplified targeted sections of DNA from their herbal samples–the first in a series of procedures that also included creating a library of amplified plant genes in E. coli bacteria.
The isolated plant genes were shipped to a corporate vendor for DNA sequencing, and the students soon received back their herbal supplement DNA sequences. They input the sequences into a computer program that allowed them to determine the true plant species found within their supplement.
"No one really got anything too unexpected this year," Barsoum said. "All the results were fairly straightforward."
Five of the 17 supplements tested yielded usable DNA. From these five supplements, the majority of the students found supplement ingredients true to their labels.
Students also found significant amounts of DNA from inactive ingredients within their herbal supplements.
"We end up finding a lot more rice powder than the actual herb you're supposed to be ingesting," Barsoum said.
Inactive ingredients, or fillers, such as rice flour, often appear to outweigh the actual herb advertised on the label in order to make the capsule the appropriate size for swallowing.
Researcher Tiffany Onia '20 extracted DNA from the herbal supplement ground turmeric after what she described as a lot of hard work and a bit of luck.
Onia's results indicated unexpected sequence matches for her particular turmeric supplement.
"The sequence alignments do not suggest an accurate match for turmeric," she said. "I haven't really gotten anything but rice and bamboo."
Last year, Barsoum's RISE team found that as much as 20 percent of genes tested for a particular brand of supplement were derived from Cannabis, a possible contaminant species.
The research experience changed the students' perceptions of dietary supplements.
"It's made me much more wary of herbal supplements," Jones said. "They might not be what they claim they are."
Likewise, Onia has drawn some strong conclusions based on her work in the lab.
"I would not trust any of this. There is no concrete science to support any of these statements: powerful antioxidant, anti-inflammatory, supports cardiovascular health," she said. "These are just hot phrases to just put on the label."
The public's implicit trust of labels presents a significant danger, Barsoum said.
"You should question and investigate dietary supplement products before consumption," he said.
Ultimately, Barsoum said, the onus is on the consumer–with dietary supplements, buyer beware.
Emily Sirota '20