Retronasal Olfaction

A role for lung retention in the sense of retronasal smell
Mouth to nose breathing occurs when odors originate in the oral cavity and pass directly to the nose. This is typical of retronasal olfaction. Unlike mouth-to-lung or nose-to-lung breathing where as much as 58% of the aromatic molecules are retained in the lungs, in mouth to nose breathing, lung retention does not occur and the aroma has a more potent effect on the olfactory receptors when one breathes out.

Differential Neural Responses Evoked by Orthonasal versus Retronasal Odorant Perception in Humans
The brain response to a chocolate odor differed depending upon whether it was sensed orthonasally or retronasally.
Researchers believed this different response is due to the perception of the availability versus the receipt of a food award. This research is important in establishing perceptional differences based upon how odors are breathed.

High-Resolution Time–Intensity Tracking of Sustained Human Orthonasal and Retronasal Smelling During Natural Breathing
These data indicate, with high-resolution tracking during natural breathing of continuously presented vapor-phase stimuli, that intensity of smelling increases to a maximum after initial intensity is perceived, and that smelled intensity then declines slowly during approximately the first minute of smelling, which speaks to how quickly we experience sensory adaptation.

Sensory Adaptation

Olfactory adaptation is dependent on route of delivery
In this study, researchers found that sensory adaptation occurred for odorants (linalool and vanillin—two common blend constituents) that were administered orthonasally (through the nostrils) but not retronasally (through the oral cavity and out the nose). In fact, regardless of elapsed time or dose, retronasal adaptation did not occur.

Forest Bathing Literature

Cardiac Health/Blood Pressure

The physiological effects of Shinrin-yoku (taking in fore forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan
Experiments conducted in 24 forests in Japan revealed that “forest environments promote lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than do city environments” suggesting that forest therapy may be an effective preventative care strategy.

Physiological and psychological effects of forest therapy on middle-aged males with high-normal blood pressure
Using multiple biometrics, including blood pressure, urinary adrenaline, and serum cortisol, as well as mood profiles, researchers found that time in a forest may be a promising treatment strategy to restore blood pressure to optimal ranges and prevent hypertension.

Effects of Short Forest Bathing Program on Autonomic Nervous System Activity and Mood States in Middle-Aged and Elderly Individuals
This study investigated changes in the activity of the autonomic nervous system and emotions after a two-hour-long forest bathing session in Taiwan in 128 middle-aged and elderly participants. Biometrics including pulse, blood pressure, heart rate variability indicated physiological benefits from the practice. The study concluded that a short forest bathing program is promising for improving heart rate and blood pressure functions, as well as enhancing relaxation.

Blood pressure-lowering effect of Shinrin-yoku (Forest bathing): a systematic review and meta-analysis
This review and meta-analysis of twenty forest bathing experiments with 732 participants found that forest bathing significantly reduces blood pressure in participants.

Immune Function

Effect of forest bathing trips on human immune function
In a review of studies examining the effects of forest bathing on human immune system function, researchers found that individuals who had practiced forest bathing experienced an increase in natural killer cell activity and expression, which boost immune system function. This increased activity lasted for more than 30 days. Additionally, the same studied participants experienced a decrease in the concentration of adrenaline in urine samples. The results were not replicated in participants who toured cities versus the forest.

Mental/Emotional Health

Physiological and psychological effects of a forest therapy program on middle-aged females
This study specifically examined the effects of forest therapy on middle-aged women and found that forest therapy has positive physiological and psychological effects, such as decreases in pulse rate, salivary cortisol levels, and increases in “comfortable,” “natural,” and “relaxed” feelings and feelings of “vigor,” in that subset of the population.

Sleep

A before and after comparison of the effects of forest walking on the sleep of a community-based sample of people with sleep complaints
This study examined the effects of forest walking on sleep and found that participants who took a 2-hour forest walk experienced better sleep characterized by a longer duration and fewer complaints than when compared to the evening prior to the exercise. Forest walking in the afternoon had a greater impact than during the morning.

Absorption/Bioavailability

 

Cannabinoid Delivery Systems for Pain and Inflammation Treatment
Traditional oral delivery of drugs, including cannabinoids, require metabolism by the gut and liver, often resulting in poor absorption. However, inhaled-pulmonary and oral transmucosal delivery formulations are absorbed directly into the bloodstream and forego first-pass metabolism. In fact, this study notes that the transmucosal dosing of opioid pain medicine was significantly superior to oral dosing of the same. Furthermore, this study showed that using terpenes as “penetration enhancers” showed promising results for improving the therapeutic effectiveness of transdermally administered CBD.

Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects
This study establishes that “terpenoids bind to odorant receptors in the nasal mucosa and proximal olfactory structures,” supporting the use of MONQ diffusers, and postulates that phytocannabinoid-terpenoid pairings (such as those occurring when CBD is mixed with essential oils) delivered to the oromuscosal membranes may be safe, effective, and synergistic.

Cannabidiol bioavailability after nasal and transdermal application: effect of permeation enhancers
CBD can be passed directly through the skin to deliver its benefits to affected areas topically. This method has been compared to oral administration in terms of efficacy, but there is reason to believe that the transdermal route provides better absorption compared to oral use by providing a more prolonged and controlled route of delivery. This study also further explores the benefits of intranasal CBD delivery, demonstrating a bioavailability of 34–46%. It ultimately concludes that intranasal delivery is likely best for sudden pain, while topical application appears best for chronic pain conditions.

The Entourage Effect

Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects
By using the phytochemistry of cannabinoids and terpenes to cross-breed these botanicals to create an entourage effect, there is unlimited potential for therapeutic application and treatment of a variety of disorders that may range from mental and cognitive health diagnosis, drug dependence, to dermatological disorders and more.

An entourage effect: inactive endogenous fatty acid glycerol esters enhance 2-arachidonoyl-glycerol cannabinoid activity
In describing the synergy that results when “the biological activity of 2-arachidonoyl-glycerol can be increased by related, endogenous 2-acyl-glycerols, which alone show no significant activity in any of the tests employed,” the authors of this study identified and coined the phrase “entourage effect.” Henceforth, the “entourage effect” has been used to describe the synergy that occurs between compounds containing at least one cannabinoid.