When I explain the science behind the sleep brand dreamt people frequently ask “What strain are you using? Indica, right? Indicas are for sleep.” While not all indicas help with sleep, these people are on to something. Specific cannabis strains do have specific effects, and some can assist with sleep. While the effects are straightforward with inhalables like vapes, flower, and extracts, edibles are a completely different story—and it’s a story many in the cannabis industry have told without fully investigating the science behind their claims.
What is a strain, and what makes an edible “strain-specific?” I could spend pages upon pages explaining cannabis strains, but for the purpose of this discussion a strain is a variety or type of plant. In general, all varieties contain flavonoids, terpenes, and cannabinoids. Some varieties contain more THC or CBD than others, but commercially available plants contain 12 percent to 30 percent THC and insignificant levels of CBD and other minor cannabinoids (except for plants especially grown or processed to produce CBD or other cannabinoids).
However, a strain from one grower or harvest can have different THC percentages than the same strain from other growers or a different harvest with the same grower. In addition, the flavonoids and other compounds may be very diluted after the extraction and the dosage. So, what really makes a strain, in this case, is the terpene profile.
Terpenes are aromatic and volatile compounds that give the signature fragrance to wood, fruits, flowers, and cannabis. Terpenes can serve as pheromones or insect repellent and provide many other functions. If used in the correct concentration and method of administration, they can have several medicinal benefits in humans.
Can you get all the benefits of terpenes in cannabis edibles? In a nutshell, no. But let me explain why. To understand the effects of terpenes we must study olfactory neuroscience, skin biology, and small-intestine physiology. The principal mechanism involved in the detection of terpenes is the olfactory, or nasal, system. The signaling pathway starts with the activation of olfactory receptor proteins in olfactory sensory neurons. The neurons send the signal to the olfactory bulb, which forwards them to various locations in the brain.
Studies have found aromatic molecules (like terpenes) can affect behaviors and physiological conditions. The neuroendocrine system that produces hormones in the brain and the endocrine system that produces hormones in the rest of the body are involved in regulating olfactory learning and sense of smell. Around 400 different types of functional olfactory receptor genes occur in humans, so the olfactory system is very specialized.
Terpenes’ effects depend on the routes of administration. For example, β-caryophyllene and linalool are both present in lavender essential oils. But although topical application of β-caryophyllene improves cell regeneration in cutaneous wounds, inhaling lavender essential oil does not produce that impact. Linalool, on the other hand, produces an anti-anxiety effect mediated only through the olfactory system. This indicates the method by which terpenes are applied should be adjusted depending on the specific terpene and expected function.
For example, a diffuser must be used for lavender essential oil when the expected effect is the anxiety-reducing impact of linalool. In contrast, lavender essential oil should be applied topically when the goal is to enhance wound healing by β-caryophyllene. Notice linalool doesn’t have an effect on the skin.
In 2014, researchers at the University of Cambridge in England discovered the human olfactory receptor OR2AT4 is expressed in the epidermis and hair follicles. The authors suggested a possible use of sandalore (a terpene derived from sandalwood) in improving wound healing and avoiding thinning hair. Other studies found terpenes like limonene, linalool, and citral also interact with olfactory receptor OR2V1 and enhance the microbiota in the guts of mice. Olfactory receptor OR2V1 is expressed in both the large and small intestines.
A study published in the Journal of Neural Regeneration Research demonstrated the olfactory receptor OR51E2 is expressed in some, but not all, the enteroendocrine cells in the colon. In a separate study, the activation of OR51E2 in the small intestine was involved in regulating blood pressure, as well. It is important to notice all these receptors are present only in the small and large intestine and not in the stomach.
So, how does all this relate to edibles? As always, the effect depends on the dose. In a study published in the Journal of Physiology and Behavior in 2015, researchers discovered administering geraniol directly into the stomach via a tube (gavage) in a dose of 20mg to 40mg per kilogram had an anti-depressant impact. This means a person would have to introduce 1.2g to 2.4g of terpene directly into their stomach—bypassing the mouth—to produce a similar effect. Other studies have used enteric capsules, which are designed to resist the acidic environment of the human stomach during the digestive process so the terpenes can reach the intestines (where the receptors are).
Many studies have investigated consuming liquids or swallowing capsules to confine the terpene exposure primarily to the gastrointestinal system, but the doses required to produce noticeable effects ranged from 20mg to 200mg per kilogram. This means humans would require an edible containing 1,200mg to 12,000mg to feel effects. Those are massive doses.
An edible’s food composition plays a crucial role in terpene bioavailability, since they are subject to digestion within the mouth and stomach before accessing the small intestine. Mechanical and enzymatic actions, different pH conditions, as well as transformation into compounds that typically are more water-soluble and readily excreted in the urine affect this process.
Usually, a 10mg THC edible contains insignificant amounts of terpenes. If the edible is from a strain-specific butane hash oil extract (up to 3-percent terpenes), terpenes will be present at about 0.33mg per dose. If the extract is a high-terpene, full-spectrum concoction (up to 40-percent terpenes, which is the highest concentration of terpenes possible in an extract) users will consume around 7mg per dose (which would taste horrible). Even that is still almost 200 times less than the minimum terpene concentration that has been demonstrated to have a pharmacological effect via oral administration. In addition, the terpenes in the edible will suffer degradation from the harsh acidic condition in the stomach. Even if the terpenes reach the intestine—the place where they are more likely to be absorbed—the desired “strain-specific” effect is not guaranteed. As mentioned before, the receptors found in the olfactory system, on the skin, and in the intestine produce dramatically different effects.
The strain-specific edible is a marketing gimmick. Consuming terpenes in an edible simply does not provide enough of the active ingredient to produce any effect. In the best possible (but worst tasting) scenario, a user would consume 200 times less than he or she would need to feel any terpene effect, and even then, there is no guarantee the terpenes wouldn’t be completely degraded by the stomach. Even if the terpenes reach the intestine, those receptors might not produce the same results produced by inhalation.
Carolina Vazquez Mitchell is a pharmacologist and the creator of Luchador and cannabis sleep aid dreamt, which she formulated to treat her own insomnia during chemistry PhD studies at the University of Southern California. She has developed more than fifty cannabis products, ran a cannabis testing lab, and was named one of DOPE Magazine’s Outstanding Women in Cannabis.