The professor of human physiology at Liverpool John Moores University and Head of Nutrition to England Rugby and The DP World Tour Golf gave the warning in an information-packed session as part of the Arizona State University Performance Nutrition series.
Titled “CBD: Could this be the shortest lived of all nutritionist fads?”, the session explored the unclear regulatory landscape and body of evidence behind the ingredient which has gained huge interest from athletes across the globe.
Close, who has conducted extensive research into sports nutrition and CBD, said athletes are understandably highly interested in these supplements but that there have been instances of athletes failing anti-doping tests after using them.
He explained CBD is sold as: full spectrum, containing all the cannabinoids in the cannabis plant including THC; broad spectrum, with all the cannabinoids except THC; isolate, which only contains CBD; or synthetic, which comes from a lab as opposed to the plant.
WADA (World Anti-Doping Agency) defines a cannabinoid as a compound produced by the cannabis plant and prohibits all natural and synthetic cannabinoids except for CBD.
This is where many athletes trip up as they assume the WADA legislation only refers to THC, he said, adding that the agency needs to make it much clearer which cannabinoids they are testing in order for athletes to know what supplements they can safely take.
Legal status
And it’s not just WADA wording that complicates the market. The legal status of CBD is "one of the most complex of all supplements in existence”, the former professional Rugby League player said.
Its status across EU Member States is mixed, from 100% illegal to unrestricted, with many shades of grey in between.
In the UK “it appears companies who have submitted a novel food application are able to continue to sell for now but cannot make any claim or even give any advice of how to take it”, he explained.
In the U.S., it is legal in some states but “more illegal than not” at a federal level. And elsewhere the picture is hugely variable with Hong Kong and Dubai considering it a dangerous drug and imposing lengthy prison sentences for possession.
There is also cause for concern over content and label claim accuracy, Close noted, adding that a UK study looked at over-the-counter CBD products and found illegal levels of THC in several products “so the industry isn’t representing itself well”.
Looking at the risk of unintentional doping, he warned: “If an athlete is buying a CBD product, there is a good chance they will fail an anti-doping test if WADA is testing for other cannabinoids.”
The other concern is that THC could accumulate in the body, and exercise can lead to its release from adipose tissue thereby increasing the risk of a failed test, he added.
CBD for athletes
Close noted that many athletes are googling “CBD and athletes” and reading that it can help with inflammation, pain relief, anxiety and depression.
“We know that athletes are becoming addicted to painkillers so if there’s anything less dangerous than some of these quite potent opiate based painkillers, I think its something we should explore,” he said.
His research team recently conducted cell-based research (as yet unpublished), treating cells with 10 micromolar CBD but “couldn’t see anything going on from an inflammatory cytokine perspective”. They also “didn’t see anything in terms of DOMS and inflammation” in a simple muscle soreness study.
However, he noted that the low allowable quantity of CBD makes it difficult to achieve the health benefits that researchers are seeking. The UK recently dropped the safe upper limit of CBD to 10 mg per day although the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney determined a safe level of 3,000 mg and that users will not experience much benefit at a dosage of under 300 mg.
That said, there is some evidence from rodent models that CBD may support muscle regeneration.
Close's team has also conducted transcriptomics research (the study of an organism’s RNA transcripts) that suggests that CBD may have a beneficial effect on oxidative stress but noted significant differences between the synthetic and plant-based supplements.
“There is a suggestion that for CBD to be effective it needs the other cannabinoids—known as the entourage effect," he explained. "And this might be something we are seeing with these studies from a muscle damage and muscle regeneration perspective.”
Science also seems to back the claim that CBD can support sleep quality, he said, most likely when the poor sleep is anxiety related. In addition, some promising rodent research indicates that prophylactic use of CBD could reduce the risk of traumatic brain injury, which he noted could be a game-changing discovery, “so somehow we really need to explore this in more detail”.
What next?
Close concluded that he doesn’t believe CBD will just be a fad as there is promising science behind the health claims but said that the regulations “currently make it impossible for athletes to explore at the moment” and that they may be turning to other supplements for similar health benefits.
“Maybe mushrooms are the next kid on the block,” he said.