- A new study shows evidence that extremely high doses of CBD can be damaging to the liver.
- But experts say this research, which was done in mice, is still in the early stages, and more information is needed.
- CBD isn’t regulated by the Food and Drug Administration, but the agency has been cracking down on companies claiming certain health benefits from taking CBD.
The market for products containing cannabidiol (CBD) — the non-psychoactive, pain-relieving chemical in cannabis — has exploded in recent years, but the product is still relatively understudied.
That’s drawn scrutiny from the Food and Drug Administration (FDA) and other regulators as manufacturers make claims on their CBD products that aren’t necessarily backed by science.
Now, a recent mouse study has been making headlines for the findings that taking too much CBD might lead to liver damage in high enough quantities.
Should you be worried? We took a look at the study and talked to experts about what this mouse study can mean for human fans of CBD.
Citing a “lack of comprehensive toxicological studies devoted to CBD safety that are critical for further marketing of CBD and CBD-containing products,” researchers from the University of Arkansas investigated the effects of treatments of various doses of CBD on a group of 8-week-old mice.
While the mice largely tolerated the CBD, those given the highest doses — a human equivalent to 200 mg of CBD per kilogram of body weight of CBD — showed clear signs of liver toxicity, the researchers found.
In addition, repeated doses of a smaller amount of CBD — the human equivalent of around 50 mg of CBD per kilogram of body weight — also showed signs of liver swelling and damage.
“Although (a dose of) 200 mg of CBD per kilogram of body weight is not applicable to most real-life scenarios, it does provide critical information regarding the potential consequences of CBD overdose as well as for doses needed for further subchronic and chronic toxicity studies,” the authors, publishing in the journal Molecules, wrote.
That sounds potentially dangerous, but most experts say there’s no need to panic just yet.
While experts point out patients need to be informed about what they’re getting and what the risks can be, the amount of CBD the animals were exposed to is far higher than what most humans would take.
Dr. Diana Martins-Welch, attending physician in palliative medicine at Northwell Health in New Hyde Park, New York, says even though CBD is ubiquitous, it does “not mean it is safe to take in high quantities, or that it is more effective at high doses.”
“Many people know that taking too much ibuprofen or Tylenol can have detrimental consequences. CBD is no different. Generally speaking, therapeutic CBD doses range from 0.5 mg/kg/day to 20 mg/kg per day,” Martins-Welch explained. “This study in mice used significantly higher doses of CBD than what is usually taken for therapeutic benefit in humans.”
She points out the study shows how — similar to other medications — people need to be careful if they consume high doses of CBD.
“Caution must also be taken when trying to translate the results of this animal study to humans,” Martins-Welch said. “Bottom line: Therapeutic-range CBD is generally safe. Toxicity at high doses is a concern, as is the case with most other medicines.”
Dr. Thinh Vo, director of quality and compliance at Koi CBD, a purveyor of lab-certified CBD products, says CBD users need to remember mice and people are pretty different.
“Mice and humans may share virtually the same genes, but we are different physiologically,” Vo told Healthline.
In addition, he said, “Extrapolation of this research shows no negative effects on a human at the recommended maximum daily dosage of 20 mg/kg.”
And even that is extreme, says Jason Cohen, founder of the CBD company Tesséra Naturals.
“A big caveat to this study is that the mice were given doses that were the human equivalent to the maximum recommended dose of the drug Epidiolex, which is a specific prescription drug meant to treat seizures,” he said.
“To put that in perspective, that would be over 1,300 mg of CBD per day for an adult weighing 150 pounds! This is much higher than the typical daily dose of casual CBD oil users. Most people stick to somewhere in the range of 10 to 80 mg per day, with slightly higher doses for insomnia, therapeutic effects, and flare-ups,” Cohen said.
So, sticking to the right dose appears to be safe for the time being. But that doesn’t mean CBD users are completely risk-free.
There’s no federal regulation for many CBD products sold OTC, so you may be taking more or less of the substance than is advertised on a product.
In the last few years, the FDA has sent a slew of warning letters as a result of CBD products being sold with either
“Furthermore, a recent independent analysis performed by ConsumerLab.com revealed that CBD doses in commercially-available products ranged from as little as 2.2 mg to as much as 22.3 mg, further amplifying concerns of potential toxicity,” the study authors noted.
Other studies have corroborated this issue.
A recent report by cannabis testing lab CannaSafe to California’s Bureau of Cannabis Control (BCC), for example, stated that somewhere between 69 and 80 percent of CBD products failed to make label claims.
What the CBD market needs is “accreditation for all tests and traceability and introduction of stability testing and shelf labeling like the FDA requires for all food products and supplements,” the company told Healthline via email.
They point out that the BCC in its capacity as a state regulator of cannabis products has already made them measurably safer. Under the bureau’s oversight, contamination of pesticides in cannabis products fell from 25 percent to under 5 percent.
While the headline-maker of the University of Arkansas study revolves around overall liver toxicity, the research highlights another little known problem with CBD: It has the potential to negatively interact with other prescription drugs.
“Our liver has a family of enzymes called cytochrome P450, which break down drugs into smaller bits that allow our cells to absorb them better and eliminate them properly,” Cohen said.
“Although the effects have been shown to be minimal, if you take high enough amounts of CBD, it can inhibit the CYP450 enzyme’s ability to metabolize certain pharmaceutical drugs,” he said.
While the FDA works on improving its oversight and regulatory structure, the best thing a consumer CBD user can do is buy from a marketplace that offers transparent laboratory testing, possibly favoring states that already have firm CBD regulations in place — and to use the products in moderation.
Is CBD legal? The 2018 Farm Bill removed hemp from the legal definition of marijuana in the Controlled Substances Act. This made some hemp-derived CBD products with less than 0.3% THC legal at the federal level. However, CBD products containing more than 0.3% THC still fall under the legal definition of marijuana, making them illegal at the federal level. Some states have legalized CBD, so be sure to check state laws, especially when traveling. Also, keep in mind that the FDA has not approved nonprescription CBD products, and some products may be inaccurately labeled.