Adapted from Optimum Nutrition Spring 2020


Cannabidiol (CBD) is one of over 100 cannabinoids derived from the hemp plant. These chemical compounds are structurally similar to the body’s own endocannabinoid system, which consists of receptors located all over the body and brain, regulating sleep, appetite, anxiety and pain.

CBD doesn’t bind directly to these receptors but it does modify their ability to bind to other cannabinoids, influence other types of receptors and enhance natural levels of endocannabinoids — supposedly providing therapeutic effects.

Unlike medical marijuana, CBD is non-psychoactive. It has also attracted increased attention in recent years. Between four to six million people in the UK have tried CBD, with the UK market worth £300 million in 2019. It’s expected to fall just short of £1 billion by 2025.

Why do people use CBD?

Epilepsy: One of the most widely claimed benefits of CBD is in the treatment of severe forms of childhood epilepsy that don’t always respond to anti-seizure medication. One study comparing two doses of CBD to a placebo found a 41.9 per cent reduction in ‘drop seizures’ in patients taking 20 mg/kg CBD per day, a 37.2 per cent reduction in those taking 10 mg/kg, and a 17.2 per cent reduction in the group given a placebo.

Chronic pain: It has also been suggested that CBD applied topically on the skin could help to lower pain and inflammation caused by arthritis. One study showed that both 6.2 and 62 mg/day were effective doses. Another study found that CBD inhibits inflammatory and neuropathic pain; two types of chronic pain that are most difficult to treat. However, both studies were carried out on animals so further research is needed.

Mental health and sleep: CBD oil may hold benefits for anxiety-related disorders and sleep deprivation. When patients in a psychiatric clinic were administered CBD alongside their usual treatment, it was found that anxiety scores within the first month decreased in almost 80 per cent of patients and remained decreased for the duration of the study. Sleep scores also improved in 67 per cent of patients but fluctuated over time. Separate research has found CBD to have considerable potential as a treatment for multiple anxiety disorders, including generalised anxiety disorder, panic disorder, OCD, social anxiety disorder and PTSD.

Is CBD safe?

Currently, CBD is not considered harmful. One study found that an oral dose of 600 mg CBD oil did not differ from a placebo on a Visual Analogue Mood Scale and subjective level of intoxication or psychotic symptoms. However, a more recent study has cautioned that CBD containing products may alter the effects of some prescription drugs.

In contrast, tetrahydrocannabinol (THC), the other well-known compound in the cannabis plant, was associated with subjective intoxication and euphoria, as well as increased psychotic symptoms and anxiety.

Can you become tolerant to CBD?

Regular use of many substances and medications can lead to the body developing a tolerance, which means less sensitivity to the active ingredients. This is a known problem in the use of conventional over-the-counter and prescription painkillers, whereby patients need to take higher doses in order to experience relief.

Currently, evidence into the potential tolerance effects of CBD in humans is limited, but one study did find that when patients with various forms of epilepsy used CBD for an average of 20 months, 25 per cent developed tolerance after an average of 7.3 months. These patients then received an increased dose; four returned to their previous response levels, while 10 had a response that was “satisfying but less than [the] prior response level”.

Is CBD legal?

CBD is legal in the UK and can be classed as a food, medicine or cosmetic. Each category is overseen by a different body.


In January 2019, the European Food Standards Agency placed CBD extracts into a category called ‘novel foods’: foods that have not been consumed to a significant degree by humans before May 1997. This requires companies to submit a dossier of evidence (including product ingredients, manufacturing process and evidence that the product is safe for general consumption) to the EU to get approval. However, this process can take two to three years, meaning there are many products on the shelves which do not have novel food approval.

The UK’s Food Standards Agency (FSA) set a deadline of 31 March 2021 for the CBD industry to submit valid novel food applications. Only products that have submitted a valid application are allowed to remain on the market.


Any product containing CBD that is used for medicinal purposes is regulated by the Medicines and Healthcare products Regulatory Agency. Unlike foods, the content of medicines must be within a certain specification every time, otherwise it cannot go to market. Manufacturers of CBD-based products must also avoid making any medical claims.

If you are considering using CBD, consult a GP before using.

For articles and recipes subscribe to the Optimum Nutrition newsletter