Cannabidiol (CBD): Claims, risks and unanswered questions

Background

Cannabis is a herbaceous plant that is perhaps best known for its role as a recreational drug. There is however growing interest in some of the specific cannabinoids found within the plant and the potential benefits that these may possess from both a medical and athletic perspective.

The plant species Cannabis Sativa contains over 140 different cannabinoids. The plant can be grown to produce “hemp” and “marijuana”. Although the actual plant species is the same, the law distinguishes between “hemp” and “marijuana”. Legally, the key difference between the two is tetrahydrocannabinol (THC) content. THC is the main psychoactive compound (the correct term is psychotropic). However there are other cannabinoids that may affect sleep, pain, inflammation and other effects, but without psychoactive effects. Cannabis Sativa must contain less than 0.2-0.3% tetrahydrocannabinol (THC) (the psychotropic cannabinoid) to be classed as hemp, which is then considered as a non-psychoactive source.

Legally, the key difference between "hemp" and "marijuana" is tetrahydrocannabinol (THC) content

The cannabinoid cannabidiol (CBD), also found in non-psychotropic hemp, is of particular interest due to its proposed anxiolytic, analgesic, anti-inflammatory and anti-oxidative capacity, alongside anecdotal reports of improved sleep. In 2018, the world anti-doping agency (WADA) removed CBD from the prohibited list. This change in regulation has led to a dramatic increase in the number of athletes using CBD. Indeed, we have recently documented that 26% of professional rugby players are either currently using or have previously used some form of CBD product (1). There are however numerous answered questions and safety concerns that must be addressed prior to this becoming a routine supplement for athletes.


Safety concerns and anti-doping risk factors

Whist CBD was removed from the prohibited list in 2018, all other cannabinoids remain prohibited, so a careful risk-benegfit analysis is critical. In low doses, i.e. those typically seen in commercially available CBD supplements, CBD does appear to have a reasonable side effect profile with a recent meta-analysis suggested that the only side effects of low dose CBD in healthy populations was diarrhoea. However, it should be stressed that long-term safety studies in athletic populations using low dose supplements are yet to be performed. There are safety concerns related to liver toxicity associated with higher doses of CBD (typically used in clinical trials). Additional research is required into the safety of CBD supplementation for athletes prior to considering it as a supplement for sports performance.


Long-term safety studies in athletic populations using low dose supplements are yet to be performed

From an anti-doping perspective, it is crucial that athletes are fully aware of the complex landscape with regards to cannabinoids and WADA. Whist CBD was removed from the prohibited list in 2018, all other cannabinoids remain prohibited (THC is a threshold substance set at 150ng/ml in urine with an adverse analytical finding being reported when the value exceeds the decision limit of 180ng/ml). Given CBD comes from the hemp plant, there are concerns that other cannabinoids, including THC, may be present at high levels, which could result in an Anti-Doping Rule Violation (ADRV).


From an anti-doping perspective, it is crucial that athletes are fully aware of the complex landscape with regards to cannabinoids and WADA

It is also unknown whether small amounts of prohibited cannabinoids could accumulate in human fat tissue and then be released during periods of fasting or exercise. This has been shown to occur in regular cannabis users, and as such needs exploring in athletic contexts using CBD products. Indeed, following a 4-week supplementation period of CBD (30 mg/day), with a reported concentration < 1 mg THC, urinary THC concentrations were detectable in 50% of participants (2). Recent findings also suggest that only 15% of a selection of commercially available products in the USA were below the < 0.3% THC maximum limit (3), despite what was stated on the label. Taken together, there appears to be too many risks and unanswered questions for athletes to consider CBD supplementation until these key questions have been addressed.

Recent findings suggest that only 15% of a selection of commercially available products in the USA were below the < 0.3% THC maximum limit

Evidence of potential benefits on pain, sleep and neuroprotection

Physical performance may be in-part dependent on the athlete’s ability to recover fully. It is therefore unsurprising that athletes often seek pain relieving therapies. Despite promise in cell-based and rodent studies, evidence to suggest CBD supplementation has an anti-inflammatory effect in humans is limited. The lack of benefits reported in recent sport science literature (e.g. 4) could be due to the low doses used, lack of chronic ingestion, choice of administration route, or genuine lack of benefit of the specific CBD products in the specific situation. Given the current limitations of the research, and lack of evidence in human participants, it is too early to support the use of CBD as an alternate to standard pain medication in athletes.


Given the current limitations of the research, and lack of evidence in human participants, it is too early to support the use of CBD as an alternate to standard pain medication in athletes

Appropriate quality and quantity of sleep is vital for general health and to promote athletic recovery. It is well-reported that disruptions in sleep are common within athletes. Despite some research suggesting that CBD supplementation may improve sleep quality and disruption, other research shows no beneficial and even negative effects. Collectively, the evidence surrounding the use of CBD supplementation on sleep is mixed (5), with benefits perhaps limited to situations where poor sleep is associated with stress and anxiety. As with pain management, additional research is needed in athletic contexts before CBD could be recommended.


Concussion

A major problem in modern day sport is mild traumatic brain injury (TBI) (such as concussion). There are suggestions that CBD may be beneficial for athletes, both in terms of preventing and improving the recovery from TBI. However, to date, only one study has directly investigated the effects of CBD supplementation on the treatment TBI, and this was in mice. It was reported that CBD reduced negative neurological behaviours and biochemical changes usually observed during TBI, potentially via decreased inflammation, oxidative stress, and neuron damage. Given the risks to health associated with concussion in athletes, it is vital that future research investigates the effects of CBD in humans, particularly those at risk of brain injury, although at present it is too early to suggest CBD as a therapeutic strategy for TBI.


Summary and future directions

CBD has rapidly appeared as a suggested supplement for athletes promoted to help with sleep / anxiety, recovery and TBI. Whilst many athletes have become early adopters and now routinely use CBD as part of their recovery strategy (Kasper et al., 2020), this is a concern for practitioners due to lack of certainty with regards to the safety profile of CBD and risks surrounding inadvertent ADRV. The current advice to athletes should be one of caution, but we would strongly encourage researchers to study this fascinating supplement. Specifically, we need to assess the risk of ADRVs and the safety of chronic use, along with assessing the efficacy of CBD on the purported benefits, considering the paper-to-podium framework (6).


References

  1. Kasper, A. M., Sparks, S. A., Hooks, M., Skeer, M., Webb, B., Nia, H., Morton, J. P., & Close, G. L. (2020). High Prevalence of Cannabidiol Use Within Male Professional Rugby Union and League Players: A Quest for Pain Relief and Enhanced Recovery. International journal of sport nutrition and exercise metabolism, 1–8. Advance online publication. https://doi.org/10.1123/ijsnem.2020-0151

  2. Dahlgren, M. K., Sagar, K. A., Smith, R. T., Lambros, A. M., Kuppe, M. K., & Gruber, S. A. (2020). Recreational cannabis use impairs driving performance in the absence of acute intoxication. Drug and alcohol dependence, 208, 107771. https://doi.org/10.1016/j.drugalcdep.2019.107771

  3. Gurley, B. J., Murphy, T. P., Gul, W., Walker, L. A., & ElSohly, M. (2020). Content versus Label Claims in Cannabidiol (CBD)-Containing Products Obtained from Commercial Outlets in the State of Mississippi. Journal of dietary supplements, 17(5), 599–607. https://doi.org/10.1080/19390211.2020.1766634

  4. Cochrane-Snyman, K. C., Cruz, C., Morales, J., & Coles, M. (2021). The Effects of Cannabidiol Oil on Noninvasive Measures of Muscle Damage in Men. Medicine and science in sports and exercise, 10.1249/MSS.0000000000002606. Advance online publication. https://doi.org/10.1249/MSS.0000000000002606

  5. McCartney, D., Benson, M.J., Desbrow, B. et al. Cannabidiol and Sports Performance: a Narrative Review of Relevant Evidence and Recommendations for Future Research.Sports Med - Open 6, 27 (2020). https://doi.org/10.1186/s40798-020-00251-0

  6. Close, G. L., Kasper, A. M., & Morton, J. P. (2019). From Paper to Podium: Quantifying the Translational Potential of Performance Nutrition Research. Sports medicine (Auckland, N.Z.), 49(Suppl 1), 25–37. https://doi.org/10.1007/s40279-018-1005-2

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