Some supplement products contain substances that are harmful. Getty Images / David Malan
More than two-thirds of Americans take dietary supplements. The vast majority of consumers – 84% – are confident the products are safe and effective.
They should not be so trusting.
I’m a professor of pharmacy practice at the University of Connecticut. As described in my new article in the Annals of Pharmacotherapy, consumers take real risks if they use diet supplements not independently verified by reputable outside labs.
What are the risks?
Heavy metals, which are known to cause cancer, dementia and brittle bones, contaminate many diet supplements. One study of 121 products revealed 5% of them surpassed the safe daily consumption limit for arsenic. Two percent had excess lead, cadmium and aluminum; and 1% had too much mercury. In June 2019, the Food and Drug Administration seized 300,000 dietary supplement bottles because their pills contained excessive lead levels.
Bacterial and fungal contamination in dietary supplements is not uncommon. In one assessment, researchers found bacteria in all 138 products they investigated. Toxic fungi were also in many of the supplements, and counts for numerous products exceeded the acceptable limits set by the United States Pharmacopeia. Fungal contamination of diet supplements has been linked to serious liver, intestinal and appendix damage.
From 2017-18, dozens were hospitalized with salmonella poisoning after ingesting kratom, a highly addictive natural opioid. Thirty-seven of the kratom products studied were contaminated.
There are ways consumers can verify the quality and safety of supplements. Getty Images / Tanya Constantine
Some dietary supplements contain drugs, yet the manufacturers don’t disclose that information to consumers. Frequently, the concealed drugs are experimental and, in some cases, removed from the market because they’re dangerous. Hundreds of weight-loss, sexual-dysfunction and muscle-building products are adulterated with inferior or harmful substances.
Sometimes, the herb you think you’re buying contains little to no active ingredient. Occasionally, another herb is substituted.
The consequences for consumers are considerable. When manufacturers replaced the herb Stephania tetrandra with the herb Aristolochia fangchi in 2000, more than 100 patients developed severe kidney damage; 18 more got kidney or bladder cancer. Although the herb is now banned by the U.S., a 2014 investigation found Aristolochia fangchi in 20% of the Chinese herbal products sold on the internet.
In an assessment of CBD products, only 12.5% of vaporization liquids, 25% of tinctures and 45% of oils contained the promised amount of CBD. In most cases they held far less. A few CBD products had enough THC to put the user in legal jeopardy of marijuana possession.