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Abstract

The Dietary Supplement Health and Education Act led to a flood of poor-quality dietary supplements. The Food and Drug Administration’s (FDA’s) jurisdiction is limited to removing products proven unsafe, rather than prospectively assessing them for quality manufacturing. With so many products available, there is very little FDA oversight until reports of patient harm occur. Microbial and heavy metal contamination, adulteration with synthetic drugs (including drugs banned from the United States), substituting herbs, and fraudulently specifying ingredients on the label have all occurred. Clinicians should collectively advocate for legislative change, only recommend products tested by outside laboratories for quality, and educate consumers about the risks of using unverified products.

Introduction

The Dietary Supplement Health and Education Act (DSHEA) of 1994 specifies that dietary supplement products must be manufactured free of contamination or adulteration.1 However, it also allows them to be sold in the United States without providing proof of their quality to the Food and Drug Administration (FDA). It is up to the FDA to prove that a product is unsafe in order to take it off the market.1 “Innocent until proven guilty” for dietary supplements has proven repeatedly risky for American consumers.
Major quality issues associated with dietary supplements are highlighted in this editorial to display the full scope of dangers consumers face. It then describes what the FDA, health professionals, pharmacies, and consumers desperately need to do in response.

Microbial Contamination

Many dietary supplements need to be grown and harvested before manufacture, and in both steps, microbial contamination can result. Bacterial and fungal contamination can degrade products or, more concerning, can infect and injure patients.2 According to the US Pharmacopeia (USP), dietary supplement ingredients should have no more than 103 and 102 cfu/g counts of aerobic microbes and yeast/mold, respectively. They should also be entirely devoid of Escherichia coli, Salmonella, Staphylococcus aureus, or Clostridium species.2
Unfortunately, many dietary supplements have microbial contamination.3-6 One study analyzed 183 dietary supplement products.6 One or more toxigenic fungi/mold/yeast were found in alfalfa, coriander, echinacea, garlic, ginkgo, juniper, licorice, psyllium, and St John’s wort supplements. Potentially toxigenic molds of the genera Aspergillus, Penicillium, Alternaria, Fusarium, Eurotium, and Cladosporium were recovered from these products at levels often high enough to indicate that the organisms were growing on the product. No fungi/mold/yeast were found in the vitamin or mineral products tested. Aerobic mesophilic bacteria were found in all products tested during the course of this study, often at greater than the recommended concentrations. In several of the products, fungal and other bacterial levels were also higher than the microbial limits established by the USP.6
A total of 37 different products containing kratom were contaminated with one or more different types of Salmonella (Salmonella Heidelberg, Salmonella Javiana, Salmonella Okatie, Salmonella Weltevreden, and Salmonella Thompson) between January 2017 and May 2018, resulting in 199 adverse events, including 50 hospitalizations.3 There have been numerous other dietary supplement products recalled for Salmonella outbreaks in 2018 alone.4,5
Dietary supplement fungi/mold/yeast contamination has been linked to patient harm.7 A bone marrow transplant recipient began taking multiple oral naturopathic supplements and developed hepatic mucormycosis. Fungi, including Aspergillus, Rhizopus, and Mucor, were identified in 4 of 10 different supplements, but it was Mucor indicus from the patient’s liver aspirate that DNA sequencing found to be identical to one of the contaminated dietary supplements. A 10-year-old girl developed appendicitis and liver abscesses from mucormycetes (Absidia corymbifera), which DNA sequencing identified from a probiotic she used. A fatal case of gastrointestinal mucormycosis occurred in a premature neonate given a dietary supplement. DNA sequencing identified Rhizopus oryzae in a tissue sample that matched the dietary supplement.7

Heavy Metal Contamination

Heavy metals can cause dementia, cognitive limitation, brittle bones, and oncological adverse events, and in dietary supplements, they should not exceed recommended levels. Unfortunately, many products, especially those manufactured outside of North America, have been shown to exceed these levels, exposing consumers to these long-term health risks.
In one study, the concentrations of heavy metals in 121 dietary supplements purchased in Canada were compared with the concentrations designated for safe daily consumption by the National Science Foundation (NSF) International.8 Overall, 5% of dietary supplements exceeded the upper limit for arsenic; 1.7% of samples exceeded the levels for lead, cadmium, and aluminum; and 0.8% of samples exceeded the levels for mercury. The average concentrations of these heavy metals were compared against those seen in the subset of products that were manufactured in North America and with 49 prescription drugs. The prescription drug arm is an important comparator because drugs are required to mitigate incorporation of heavy metals. The dosages of arsenic (21.7 vs 0.782 vs 0.0069 µg), lead (1.49 vs 0.362 vs 0.0237 µg), cadmium (0.199 vs 0.0918 vs 0.0035 µg), aluminum (21.7 vs 0.782 vs 0.0069 µg), and mercury (0.366 vs 0.0007 vs 0.0146 µg) were much higher in dietary supplements overall when compared with those manufactured in North America and orders of magnitude higher than in prescription drugs, respectively. These same trends were found for barium, antimony, thallium, tin, and cesium, although no product exceeded the maximum daily dose threshold.8
The prevalence of metals in Ayurvedic medicine products purchased over the internet was also assessed.9 Approximately 20% of the 193 products had excessive levels of heavy metals. Overall, 41% and 17% of rasa shastra dietary supplements (those utilizing minerals and metals for healing) were contaminated, respectively. Rasa shastra products had higher median concentrations of lead (11.5 vs 7.0 μg/g) and mercury (20 800 vs 34.5 μg/g) than non–rasa shastra products even though 75% of manufacturers claimed Good Manufacturing Practices. All metal-containing products exceeded one or more standards for acceptable daily intake of heavy metals.9 In June 2019, the FDA seized 300 000 containers from Life Rising Corporation because the products tested positive for excessive levels of lead.10 The size of this seizure shows the number of consumers who can be exposed from even 1 substandard dietary supplement product.

Prescription Drug Adulteration

In an analysis of FDA warnings issued for dietary supplement products from 2007 through 2016, unapproved pharmaceutical ingredients were identified in 776 of them.11 Many were touted for sexual enhancement, weight loss, or muscle building. In all, 20% of the dietary supplement products containing more than 1 unapproved prescription ingredient. There were 28 products named in 2 or 3 warnings issued more than 6 months apart (meaning they resolved the adulteration issue only to re-adulterate the product at another time with the same or another adulterant). Of these dietary supplement products, 67.9% contained new unapproved ingredients in subsequent warnings. Phosphodiesterase type 5 inhibitors and diuretics are in some of the products, whereas others include banned or never FDA–reviewed drugs such as daptoxetine (international drug), fenfluramine, sibutramine, and phenolphthalein.11 In assessing FDA warning letter data from 2017 to September 19, 2018, 178 new products with synthetic drugs were identified, and all except for one were used for sexual enhancement or weight loss.12 How far prescription drug adulteration in dietary supplements extends beyond these indications cannot be discerned because almost none of the products available to US consumers has been assessed.13

Substitution of Active Plant Variety or Enrichment of Product

There are many instances where the herb named on the bottle was not the same as the herb in the product (tablets, capsules) or where active ingredients in dietary supplements were enriched with higher than normal concentrations of certain natural or synthetic constituents.14-18
Dietary supplements containing kava had been used safely for years before 93 cases of presumed kava-induced hepatotoxicity (7 deaths and 14 liver transplants) occurred.14 The change in the safety profile was likely secondary to the depletion of the Piper methyticum variety of the kava plant. Manufacturers started using other varieties of kava that contained a hepatotoxic constituent called flavokavain B. The American Kava Association responded with a rigorous new certification program for cultivators and manufacturers of kava as a result.14
In 2000, Stephania tetrandra, an herb that was supposed to be contained in some multi-ingredient dietary supplement products, was replaced by Aristolochia fangchi, an herb known to be nephrotoxic and carcinogenic.15 In all, 105 patients exposed to the herb developed nephropathy, and 43 had reached end-stage renal failure; 39 of the patients with end-stage disease agreed to undergo prophylactic removal of their kidneys and ureters with concomitant biopsy of their bladder. A total of 18 cases of urothelial carcinoma, 17 cases of carcinoma of the ureter and/or renal pelvis, and 1 bladder tumor were discovered.15 Although the US bans aristolochic acids from being incorporated into any products, aristolochic acids I and II were found in 20% and 7% of Chinese herbal products sold in the United States via the internet and selected for additional scrutiny in 2014.16
Sometimes the substitution of an herb is accidental because of the inconsistent nomenclature system for Chinese herbs and the similarity of their names and appearance.17 For example, Han Fang Ji has been replaced by Guang Fang Ji, Mu Tong by Guan Mu Tong, and Mu Xiang by Qing Mu Xiang in some products.17
Herbal products can also be enriched with natural or synthetic constituents of the herbs. When kava was in short supply, some manufacturers used subpotent varieties of the plant that were naturally low in kavalactones and then enriched the products with synthetic kavain to bolster the effect.14 Kratom has 2 main constituents, the predominant mitragynine and the rarer but more potent opioid 7-hydroxymitragynine. Some kratom products were found to contain a far greater concentration of 7-hydroxymitragynine than would occur naturally, leading to suspicion that they were being enriched to enhance its opioid properties and addiction potential.18

Fraudulently Underdelivering Ingredients

The FDA does not test dietary supplement products for validation of the amount of active ingredients specified on the label.1 Furthermore, if the company chooses to have a “proprietary blend,” they only list the ingredients in descending order of weight and the total weight of all the ingredients in the blend.1 In an assessment of cannabadiol (CBD) products, only 12.5%, 25%, and 45% of vaporization liquids, tinctures, and oils were labeled correctly (±10% of the labeled value) and in most cases contained far less CBD than promised.19 In addition, a few of the CBD products contained enough Tetrahydrocannabinol (THC) to put the user in legal jeopardy of marijuana possession.19
Numerous dietary supplements sold in New York State at major retailers were tested using DNA barcoding to detect the presence of the herbs listed on the label.20 The findings were similar to those of another study that tested herbal dietary supplements in North America using DNA barcoding.21 In both studies, many of the products contained little to no herbal content.20,21 As pointed out by the American Botanical Council, DNA barcoding is not appropriate for detecting extracts of herbs or herbs that are heated for a prolonged period of time in the processing or manufacturing process.22 Although it is unknown if this methodology was appropriate for all products tested in these studies, the implicated manufacturers did not provide testing results to contradict the findings.20-22 What is equally as troubling is that there was undisclosed herbal material in the products such as pine (Pinus strobus), spruce, wheatgrass, dracaena (a tropical houseplant), oryza (rice plants), Aperagaceae, Ranunculcae, primrose, French bean, wild carrot, and Phaseolus fabaceae (bean vines), which seems designed to make the products look herbal in nature.20 In addition, there was Saw Palmetto detected in a Valerian Root product, suggesting improper cleaning of manufacturing equipment. This also suggests that Saw Palmetto should be detectable in Saw Palmetto products via DNA barcoding, but in many of the products, it was not.20

What Is the Solution?

The current system has led to a “Wild West” scenario where numerous companies blatantly disregard consumer safety, honesty, and integrity. The dietary supplement industry has shown that it cannot police itself. Whereas the adverse effects from Salmonella contamination arise quickly after ingestion, many people with less severe symptoms of nausea, vomiting, and diarrhea might not attribute it to their dietary supplement.3-5 Adverse events arising from heavy metals or use of banned synthetic substances could take years to manifest and, therefore, be unattributed to the real cause.8-10,13 The point is, all the adverse events displayed above are just the tip of the iceberg.
The DSHEA Act was written to limit the FDA’s oversight of dietary products, and it has done just that.1 Health professional and consumer advocacy organizations need to come together and with one voice sound the alarm and unequivocally call on Congress to take action to prevent the inadvertent poisoning of our populace. We should not wait until another “thalidomide moment” occurs before we act. An easy amendment would require independent third-party laboratory verification of a sample of every new product before being sold in the United States, with periodic spot checking of products on the shelves. Manufacturers would have to pay for this testing and would not be able to manipulate or suppress the results.
The only other way to exact change is if consumers refuse to purchase products without independent third-party laboratory verification. There are currently 3 different highly regarded independent laboratories that verify dietary supplements: the USP, the NSF, and ConsumerLabs.com.23 Whereas USP and NSF are nonprofit organizations, they charge manufacturers for their verification services and allow companies with high-quality products (inclusion of the active ingredient, absence of pesticide and heavy metal contamination) to use the USP seal or 1 of 2 NSF seals (NSF Contents Certified for nonathletes and NSF Certified for Sport for products used by athletes subject to drug testing for banned substances). They post verified products on their websites as well.23 ConsumerLab.com is a for-profit company that not only regularly tests and certifies supplements in a funding process similar to USP and NSF, but also proactively assesses products without being paid by the manufacturers; but consumers or stores selling the products have to pay to see the individual results.23,24 Recently, UL, a for-profit company known for testing electronics, has begun certifying dietary supplements, but it is unclear if their results are reliable.23 Some manufacturers go to third-party laboratories for quality testing, and the manufacturers then post the certificates of analysis on their websites; but it is not clear how much you can trust the results.25 ConsumerLabs.com reports that sometimes the laboratories will select a testing method with low sensitivity to detect an issue, intentionally or unintentionally not perform the test correctly, test a different product and cross-report the results, or simply make up the results.25 In addition, manufacturers might use different ingredients or processes when they know they are making a batch that will be tested.
Pharmacies should only sell products that they can verify are of high quality because consumers trust their pharmacists and, by extension, might feel all dietary supplements in the pharmacy are high quality.26 In 2019, CVS pharmacies launched its “Tested to Be Trusted” program and analyzed ~1400 dietary supplements that it previously sold in its stores for truthful labeling and lack of contamination. In all, 7% of products failed, resulting in an update to the supplement facts panel or removal of the product from shelves. Other major retailers need to follow suit and have a high standard for the products they sell.
Consumers must be proactively educated by health professionals about how pervasive quality issues are in the dietary supplement industry and how risky it is to use nonverified dietary supplements. The examples given in this editorial can be shared with consumers to drive home the point that purchasing based on price, from the consumer’s country of origin, or on the word of a health writer in a magazine, blog, or on the internet is a risky endeavor that could lead to injury or even death. Health professionals should only recommend dietary supplements that are independently certified by reputable organizations such as USP, NSF, and ConsumerLabs.com.

Declaration of Conflicting Interests

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

References

1. US NIH Office or Dietary Supplements. Dietary Supplement Health and Education Act of 1994, Public Law 103-417, 103rd Congress. https://ods.od.nih.gov/About/DSHEA_Wording.aspx. Accessed October 13, 2019.
2. AALabs. Nutritional and dietary supplement microbiology testing. http://adamsonlab.com/blog/services/microbiology/nutritional-and-dietary-supplement-microbiology-testing/. Accessed November 25, 2019.
3. US Food and Drug Administration. FDA investigated multistate outbreak of salmonella infections linked to products reported to contain kratom. https://www.fda.gov/food/outbreaks-foodborne-illness/fda-investigated-multistate-outbreak-salmonella-infections-linked-products-reported-contain-kratom#time. Published June 29, 2018. Accessed November 25, 2019.
4. Larsen L. Two dietary supplements recalled for possible salmonella contamination. Food Poisoning Bulletin. https://foodpoisoningbulletin.com/2018/two-dietary-supplements-recalled-possible-salmonella-contamination/. Published January 22, 2018. Accessed November 25, 2019.
5. Whitworth JJ. Salmonella in dietary supplement. Food Navigator. https://www.foodnavigator.com/Article/2018/01/04/T.-Marzetti-King-Soba-Revogan-Wellpursan-Lidl-in-recalls?page=10#. Published January 4, 2018. Accessed October 12, 2019.
6. Tournas VH. Microbial contamination of select supplements. J Food Saf. 2009;29:430-442.
7. Benedict K, Chiller TM, Mody RK. Invasive fungal infections acquired from contaminated food or nutritional supplements: a review of the literature. Foodborne Pathog Dis. 2016;13:343-349.
8. Genuis SJ, Schwalfenberg G, Siy AK, Rodushkin I. Toxic element contamination of natural health products and pharmaceutical preparations. PLoS One. 2012;7:e49676.
9. Saper RB, Phillips RS, Sehgal A, et al. Lead, mercury, and arsenic in US—and Indian-manufactured ayurvedic medicines sold via the Internet. JAMA. 2008;300:915-923.
10. US Food and Drug Administration. FDA advises consumers to stop using certain life rising dietary supplements product: samples test positive for lead. https://www.fda.gov/food/dietary-supplement-products-ingredients/fda-advises-consumers-stop-using-certain-life-rising-dietary-supplements. Published June 14, 2019. Accessed October 13, 2019.
11. Tucker J, Fischer T, Upjohn L, Mazzera D, Kumar M. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Netw Open. 2018;1:e183337.
12. US Food and Drug Administration. Tainted products marketed as dietary supplements_CDER. https://www.accessdata.fda.gov/scripts/sda/sdNavigation.cfm?filter=&sortColumn=1a&sd=tainted_supplements_cder&displayAll=false&page=20. Accessed October 19, 2019.
13. White CM. Beware of natural supplements for sex gain and weight loss. The Conversation. https://theconversation.com/beware-of-natural-supplements-for-sex-gain-and-weight-loss-106484. Published December 7, 2018. Accessed October 12, 2019.
14. White CM. The pharmacology, pharmacokinetics, efficacy, and adverse events associated with kava. J Clin Pharmacol. 2018;58:1396-1405.
15. Nortier JL, Martinez MC, Schmeiser HH, et al. Urothelial carcinoma associated with the use of a Chinese herb (Aristolochia fangchi). N Engl J Med. 2000;342:1686-1692.
16. Vaclavik L, Krynitsky AJ, Rader JI. Quantification of aristolochic acids I and II in herbal dietary supplements by ultra-high-performance liquid chromatography-multistage fragmentation mass spectrometry. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2014;31:784-791.
17. Yang HY, Chen PC, Wang JD. Chinese herbs containing aristolochic acid associated with renal failure and urothelial carcinoma: a review from epidemiologic observations to causal inference. Biomed Res Int. 2014;2014:569325.
18. White CM. Pharmacologic and clinical assessment of kratom. Am J Health Syst Pharm. 2018;75:261-267.
19. White CM. A review of human studies assessing cannabidiol’s (CBD) therapeutic actions and potential. J Clin Pharmacol. 2019;59:923-934.
20. NYS Attorney General Office. Warning letters to manufacturers. http://www.documentcloud.org/documents/1532311-supplements.html#document/p1. Accessed October 13, 2019.
21. Newmaster SG, Grguric M, Shanmughanandhan D, Ramalingam S, Ragupathy S. DNA barcoding detects contamination and substitution in North American herbal products. BMC Med. 2013;11:222.
22. American Botanical Council. Science group says article on DNA barcode analysis of herbs is flawed, contains errors, creates confusion, and should be retracted. http://cms.herbalgram.org/press/2013/DNA_Barcoding_Critique.html? Published November 5, 2013. Accessed October 13, 2019.
23. Loria K. How to choose supplements wisely: third-party groups test them to ensure they contain what’s on the label and aren’t contaminated. https://www.consumerreports.org/supplements/how-to-choose-supplements-wisely/. Published October 30, 2019. Accessed November 25, 2019.
24. ConsumerLabs.com. Product reviews: CBD & hemp extract supplements, lotions, and balms review. https://www.consumerlab.com/reviews/cbd-oil-hemp-review/cbd-oil/. Published February 10, 2018. Accessed November 25, 2019.
25. ConsumerLabs.com. ConsumerLab.com answers: can you trust reports from supplement manufacturers? https://www.consumerlab.com/answers/can-i-trust-supplement-manufacturer-lab-reports-and-certificates-of-analysis/certificates-of-analysis/. Accessed November 25, 2019.
26. CVS Pharmacy. CVS pharmacy launches “Tested to Be Trusted” program for vitamins and supplements, launches self-care campaign to highlight purpose-led initiatives and expanded product assortment. https://cvshealth.com/newsroom/press-releases/cvs-pharmacy-launches-tested-be-trusted-program-vitamins-and-supplements. Published May 15, 2019. Accessed November 26, 2019.

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Published In

Article first published online: January 24, 2020
Issue published: August 2020

Keywords

  1. herbs
  2. dietary supplements
  3. patient safety
  4. FDA
  5. adulteration
  6. contamination

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© The Author(s) 2020.
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PubMed: 31973570

Authors

Affiliations

C. Michael White, PharmD, FCP, FCCP

Notes

C. Michael White, School of Pharmacy, University of Connecticut, 69 North Eagleville Road, Storrs, CT 06269-3092, USA. Email: [email protected]

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