Cannabis and Nutritional Health


Cannabis and Health 



Importance of Topic to Practice
Cannabis has been used for thousands of years as a recreational, spiritual and therapeutic drug. Over the last few decades, an increasing amount of research has investigated its potential to manage the symptoms associated with a variety of diseases. With a recent rise in the legalization of cannabis globally and the consequential increase in accessibility, dietitians can expect to have greater exposure to clients who have an interest in cannabis. Dietitians should be aware of the nutritional implications, safety, and side-effects associated with cannabis use both medicinally and recreationally. 
Topic Overview
What is Cannabis?
Cannabis is a plant most often associated with its use as a drug (1). The term marijuana refers to the dried flowers and leaves of the cannabis plant and is sometimes referred to as weed, herb, pot or Mary Jane. Cannabis can be consumed through a variety of methods including smoking, vapourizing, eating, drinking, tinctures, sprays, capsules and through topical creams.
Origin and Usage 
Cannabis is widely available and has historically been used for multiple purposes across the world (2). For instance, hemp, a cannabis plant species, contains fibre and seeds used to manufacture paper, fuel, oils, medicine, clothing, plastic, rope and is a source of food. Hemp foods, unlike marijuana, do not contain a sufficient amount of the necessary compound tetrahydrocannabinol (THC) to induce psychoactive effects after consumption (2). Typically, the major uses of cannabis are either for recreational or medicinal purposes (3). Statistics from 2015 to 2017 indicate that 15% of Canadians, 18% of Americans, 10% of Australians and 7% of those from the United Kingdom reported using cannabis, either recreationally or medicinally, at some point within the past year of when the studies took place.         
Public Interest
A 2017 study by Dalhousie University (Nova Scotia, Canada) revealed findings about Canadians’ perception of recreational cannabis and cannabis-infused food (4). According to the survey, 68% of Canadians agree with the legalization of recreational cannabis. Notably, 45.8% of Canadians said they would purchase marijuana-infused food products if they became available on the Canadian market. The primary interest in edibles was in the form of bakery products (46.1%) or ready-to-eat products, such as candies (26.6%). However, Canadians also reported being concerned about eating too much marijuana-infused food and worried that the effects could be too strong. The majority of Canadians did not view marijuana as a healthy ingredient. They also reported concerns about the risks for children and young adults with recreational cannabis being made available.
There are potential adverse side-effects and health concerns associated with acute and chronic use (5). The most common adverse side-effect, particularly with inexperienced users, is panic/anxiety attacks and, in some extreme cases, paranoia. This can be linked to the increase in heart rate as well as the perceptual alterations induced by THC. 
Cannabis Intoxification
Cannabis also impairs cognitive and behavioural functions, meaning that tasks that require a certain degree of attention and ability to think/react, such as driving or operating hazardous machines, should be avoided (5). Other acute side-effects include increased laughter, talkativeness and distortions to verbal fluency, reduced reaction time and impaired problem-solving ability (5). It is nearly impossible to overdose on marijuana, as one would need to consume nearly 40,000 times the amount of marijuana it takes to receive a “high” in order to overdose (6). 
Suggestions to manage and reduce harm from cannabis intoxication include avoiding driving, seeking the accompaniment of another individual to monitor symptoms, not panicking, taking deep breaths, drinking water and avoiding alcohol, changing the surrounding environment and even taking pure CBD (6). (See section What are Cannabinoids? for a brief description of CBD). If an individual feels symptoms that are severe, including difficulty breathing or prolonged nausea/vomiting, or if cannabis is consumed by a high risk individual such as a young child, pregnant woman or elderly person, immediate medical attention should be sought or contact made with a poison control centre (7).
Cannabis is contraindicated in females who are pregnant, as studies have shown it can lead to low birth weight, premature birth and increased chance of admission to the neonatal intensive care unit (8). THC-containing cannabis is contraindicated in those who have a history of psychosis and schizophrenia, as cannabis can exacerbate psychotic symptoms, and those with unstable heart disease, as THC increases heart rate (9). 
Short and Long-Term Health Risks
Multiple studies have shown that THC can be present in the blood or urine of non-smoking individuals exposed to second-hand cannabis smoke, resulting in minor physiological changes like increased heart rate and impairment to psychomotor and memory activities (10). In addition, accumulating evidence suggests that cannabis has a negative effect on adolescent neuromaturation (anatomically developing differently), which may underlie long-term cognitive and emotional deficits (11). This is explained by strong evidence that cannabis use adversely impacts synaptic pruning and white matter development, two key processes that occur during adolescence (12). 
Lung health is also a concern if smoking cannabis as an association with increased tar exposure, alveolar macrophage dysfunction and bronchial mucosal histopathologic dysfunction has been noted (13). The risk of pneumonia is also high due to its immunosuppressive effects and possible bacterial and fungal contamination. However, despite the presence of procarcinogenic compounds in cannabis smoke, epidemiologic studies have failed to demonstrate an increased risk of lung or upper airway cancer, although the results are mixed when examining the risk of heavy, long-term use. The pulmonary risk of regular cannabis consumption through smoking is much lower than that of tobacco, but consumers should still be aware of its health risks and that further rigorous studies need to be performed to reach definitive conclusions. 
Another long-term health risk is dependence and mental health. The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, fifth edition) outlines the criteria for being diagnosed with cannabis use disorder and can be further classified into different status or severity categories (13). Cannabis use disorder is associated with adverse outcomes, including cognitive decline, psychiatric symptoms, poor quality of life, other drug use and the risk of addiction or substance-use disorders, in addition to harmful non-mental health-related effects (14). Using data from the 2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions-III in which 36,309 American participants were surveyed, Hasin et al. found that cannabis use disorder has or is currently affecting 6.27% of all Americans, or nearly 15 million people in the United States (15). The prevalence of this disorder is on the rise in the United States and demonstrates the need for health care practitioners to properly evaluate signs of cannabis use disorder when having discussions surrounding cannabis use with patients/clients. 
Relevant Basic Information
What are the different types of cannabis?
Cannabis can be classified into three main types: sativa, indica and a hybrid (16). Within these types are a large number of individual strains. The differences in the first two types of cannabis can be summarized, as shown in the table below (16).
Physical Characteristics
Light green with thinner leaves, and much taller than Indica
Dark green with broad leaves, with a short and dense plant structure
Emotional Effect
Euphoric feeling
Relaxing and calming
Possible Functions
Uplifting properties may aid in depression, fatigue, appetite, pain and nausea.
The sedating effect may be beneficial for insomnia and pain relief.
Hybrid strains are a result of crossbreeding from one strain of Indica with a strain of Sativa (16). Logically, when consumed, they will exhibit effects that differ from an Indica or Sativa strain. These effects will ultimately depend on the strain of each plant that is hybridized. 
The types of cannabis are becoming less and less distinct, as most strains on the market today have been crossed at one time or another (16). Therefore, one cannot presume that the characteristics of Sativa versus Indica described above will be exactly what will be experienced when consumed. Ultimately, the differences in chemical composition, and not the name, is responsible for the differences in effects these two types of cannabis will exhibit. These chemicals are called cannabinoids.
What are Cannabinoids?
In cannabis, there are over 80 different compounds called cannabinoids, chemicals that work together to give cannabis its medicinal and recreational properties (17). The two most well-researched cannabinoids are tetrahydrocannabinol (THC) and cannabidiol (CBD).
THC is the most researched and proven of the two. It is the main chemical that is responsible for cannabis’ psychoactive effects (17). THC acts on the CB1 receptors, largely in the brain, and CB2 receptors, largely outside of the nervous system, of the endocannabinoid system. The CB1 receptors are responsible for regulating emotions, memory, pain sensitivity and appetite.
The exact mechanism of action and therapeutic potential of CBD is not clear, but its use as a medicinal agent is increasing due to its non-euphoric properties (17). CBD currently lacks well-powered, double-blind randomized, controlled studies to support its use for treating any disorders; however, a number of other studies and anecdotal support have claimed efficacy in treatment-resistant epilepsy, neonatal hypoxic-ischemic encephalopathy, anxiety, schizophrenia, pain and addiction.
Implications of Cannabinoids on Human Health
A number of studies have investigated cannabis use as a medicinal agent to manage certain health conditions (18). Many of these studies use THC, cannabis (e.g. smoked leaves or cannabis extract) or a specific approved cannabis medication; very few use CBD in isolation.
Many studies completed in the 1970s and 1980s investigated the efficacy of THC and Nabilone on cancer chemotherapy-induced nausea and vomiting (18). Nabilone (Cesamet™) is a Health Canada-approved cannabinoid and is structurally similar to THC, which can therefore induce similar adverse side-effects (19). Individuals with cancer or HIV and presented with appetite loss and cachexia have also been studied and treated with inhaled cannabis and THC (18). No current Health Canada cannabinoid medication exists for this population. Perhaps the most well-researched area is neuropathic and chronic pain, which includes pain from upper motor neuron disease, allodynia, diabetic peripheral neuropathy, spinal cord injury, multiple sclerosis and others. THC, as well as a Health Canada-approved cannabinoid oral spray called Sativex, a specific extract of cannabis containing both THC and CBD, were most commonly used in these studies. 
A number of other medical conditions are being investigated to determine if cannabis may help manage certain symptoms, although evidence from these trials is currently limited (18). One area with potential is the use of cannabis to manage Crohn’s disease symptoms (20). Other areas with preliminary research include irritable bowel syndrome, Tourette syndrome, spinal cord injury, glaucoma, post-traumatic stress disorder, attention deficit hyperactivity disorder, migraines, anxiety disorders, schizophrenia, dystonia and some forms of epilepsy (18).
Delivery Methods
There are several methods in which cannabis can enter the human body and induce psychoactive and medicinal effects (1). Cannabis can be inhaled by way of smoking or vapourizing. It can also be ingested orally or applied topically (1). Smoking cannabis on a regular basis is associated with a chronic cough and phlegm production, poor lung health, social disapproval and can release unpleasant odours (21). However, smoking cannabis is seen as convenient, affordable and allows for more control over symptoms due to the immediate onset of effects (22). Individuals suffering from pain may gravitate towards smoking for immediate pain relief (within minutes), with the duration of effects lasting anywhere between two and six hours. Vaporization of cannabis has a similar onset and duration, as well as a similar sensory effect to smoking. It is also seen as being more discreet as less odour is produced, and many individuals report vapourizing “tastes” better than smoking. Oral methods of delivery (eating, drinking, capsules and tinctures) are convenient, discrete and have long-lasting effects ranging from three to nine hours depending on stomach content and type(s) of food consumed with the cannabis. However, oral methods can be more expensive and more difficult to control in terms of onset, dosage and titration, as it may take between 30 to 120 minutes to feel the effects. Ingesting cannabis orally through baked goods is also associated with higher fat and sugary foods, which may make ingesting cannabis, a naturally bitter substance, more enjoyable. Lastly, cannabis can be administered topically to reduce localized pain, soreness and inflammation; however, there is little research investigating its effectiveness. The THC from topical cannabis does not produce psychoactive effects unless administered transdermally.
Regulatory Issues 
Government Website
Not legal, except in Canberra
United Kingdom
Not Legal
United States
Some states
Some states
No federal website is available, only individual state websites.
Medical cannabis is legal throughout Australia with a doctor’s prescription (23). Recreational use is illegal with the exception of Canberra, the Australian capital. It is the only city that has passed legislation for recreational cannabis to be legal (effective Jan 31, 2020) and permits possession of 50 g of dried cannabis and growing up to two cannabis plants at home per person with a maximum of four plants per household (24). The smoking or use of cannabis in Canberra must not occur in a public place, amongst other rules.
Bill C-45, also known as the Cannabis Act, was passed by Parliament, thereby creating a strict legal framework for the production, distribution, sale and possession of recreational cannabis across Canada as of October 17th, 2018 (25). Adults who are 18 years and older are able to possess 30 grams of dried cannabis or equivalent in dried form (26). They can purchase cannabis from a provincially licensed retailer, and Canadians are permitted to grow up to four cannabis plants per residence for personal use from licensed seeds or seedlings, although some provinces are aiming to ban the home growing of cannabis. Additionally, Canadians are permitted to make cannabis products, such as food and drinks, at home. Commercially sold edible products have been legal since October 17th, 2019 and are now available for sale through government stores and websites as of December 19th, 2019 (26). Edible products must contain 10 mg THC or less per package and must abide by strict packaging, labelling and product rules (27). For more information regarding the legalization of cannabis, see Health Canada’s website.
United Kingdom
The legalization of medical cannabis in the United Kingdom occurred in November 2018 (28). Cannabis remains illegal for recreational use and is categorized as a ‘Class B’ drug. Possession of cannabis can range from a fine to up to five years in prison, and involvement in the supply and production of cannabis could warrant up to 14 years in prison, a fine or both.
United States
Unlike Canada, cannabis is federally illegal in the United States (29). However, certain states have passed legislation that permits the legal use of solely medicinal cannabis, or medicinal and recreational cannabis. Medicinal use is legalized in 35 states and the District of Columbia (D.C.), and recreational use is legalized in 15 states and D.C. Each state controls its own regulations regarding THC amount, possession amount, purchasing and more. Twenty-seven states and D.C. have decriminalized the possession of small amounts of cannabis. 
Dietitian Scope of Practice 
Understanding a dietitian’s scope of practice is essential in providing safe, ethical and client-centered nutritional care. Canadian provincial regulatory bodies have released position statements or question and answer documents on cannabis and dietetics' scope of practice (30-33), with the following themes:
  • Understand the evidence and literature of both the health benefits and dangers of consuming cannabis, including the quality of the studies and acknowledging that there is limited published literature.
  • Use your professional judgement to determine if a client’s question about cannabis pertains to the nutritional health of your client and whether you have the knowledge, skills and judgement to provide safe, ethical and competent advice. If not, consider referring this client to another health professional.
  • As a dietitian, you may not provide clients with cannabis recipes, as that is analogous to providing a client with a controlled drug prescription. While you may discuss the nutritional implications of cannabis with a client, you are prohibited from prescribing and/or recommending cannabis no matter the method of administration (smoking, pills, edibles, etc.)
  • The Cannabis Act prohibits the advertising, promoting or selling of cannabis to minors (age varies per province). Therefore, because of the presence of minors on social media, it is not recommended to advertise products or services on social media platforms.
The above recommendations are not a complete summary of the rules and regulations for safe and ethical practice of cannabis. It is recommended that each practitioner review their governing body’s statement (if provided) and contact them if there are questions about the scope of practice with cannabis. 
Resources for Professionals
Practice guidelines, web links, other professional tools and resources can be found under the Cannabis and Nutritional Health Related Tools and Resources tab. Use the Audience, Country and Language sort buttons to narrow your search.
Additional Resources/Readings for the Professional
Description: A review published in the European Journal of Internal Medicine of the conclusive/substantial, moderate/limited and insufficient/no evidence of the therapeutic effects of cannabis. 
Description: An in-depth review for professionals published in Gastroenterology and Hepatology of the current evidence of the therapeutic effects of cannabis on inflammatory bowel disease (Crohn’s and ulcerative colitis).
An allergy to cannabis is not commonly diagnosed, yet with its changed legal status in many countries and therefore more people willing to self-report, the prevalence of cannabis allergies is expected to grow (34). Depending on method of consumption as well as individual reactions, symptoms can range from mild to life-threatening (34). Respiratory symptoms, including rhinitis, conjunctivitis, asthma and palpebral angioedema (eyelid swelling) from smoking, vaping, and second-hand smoke have been documented in the literature, as well as urticaria (skin rash) and dermatitis from direct handling and even anaphylaxis from oral ingestion (35). Diagnosis of an allergy is similar to that of other allergy testing available: skin-prick tests and/or a serum measurement of IgE antibodies. Like other allergies, there is no cure, and the best way to treat this allergy is through full avoidance.
Of particular interest is what researchers describe as cannabis fruit/vegetable syndrome. This syndrome is when someone consumes enough cannabis to become hypersensitive to a protein found in cannabis, resulting in a cross-reactivity with a structurally similar protein found in some fruit and vegetables (or plant-based foods), including peaches, apples, nuts, tomatoes, bananas, cherries, wheat, beer, wine and tobacco (34). This allergy is not unidirectional, i.e. new allergies to the foods mentioned above are not always a result from overexposure to cannabis; rather, one can develop allergies to cannabis from the consumption of fruit/vegetables with similarly structured protein (35). Treatment comprises avoiding foods the individual is allergic to as well as to halt further cannabis use, especially if an allergy to cannabis is present (36).
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Target Group: All Adults
Knowledge Pathways: Cannabis and Nutritional Health
 Last Updated: 2021-06-09

Current Contributors


Timothy Lau - Author

Jodie Relf - Reviewer

Shannon Mackenzie - Reviewer

Shannon Robichaud - Reviewer