While you walk outside and take in all of nature’s unique scents, you are smelling the unique aromatic compounds produced by the plants. These smells are caused by something known as terpenes.
Terpenes work together to create the characteristic fragrance of most plants, such as lavender, citrus fruits, pine, and peppercorn. In nature, they protect plants from infectious bacteria, insects, and grazing animals. They might even offer health benefits for us humans.
What Exactly Are Terpenes?
Terpenes were first isolated and defined in the 1800s, but our awareness of them goes back to the beginning of time. They are hydrocarbons present in the essential oils produced by nature. There are over 20,000 terpenes in existence, and the search for more continues today. Plants, animals, fungi, and microbes have them to carry out necessary biological functions to both thrive and survive. These compounds serve as vitamins, hormones, and pheromones and are part of the plant’s immune system.
Certain terpenes, like terpinolene and linalool, attract insects and other small creatures that can help spread pollen. Others, like geraniol, scare away bugs or herbivores that might be tempted to snack on the plant. They also support the plant’s immune system by conveying information about the surrounding environment, protecting plants from stressors and pathogens, and helping to trigger immune responses.
One way to think of them is as building blocks created by plants. These building blocks are combined with other aromatic compounds in countless ways to produce complex essential oils, such as Citrus, Eucalyptus, Lavender, etc.
In addition to unique aromas, terpenes play a role in how we taste, smell, and feel when consumed by a plant, fruit, or herb. This happens because they interact synergistically with other plant compounds and our hormones to create the “entourage effect.” This phenomenon is thought to enhance the benefits of the plant’s components. There are many diverse applications for isolated terpenes and different blends of them. Terpenes are used to develop food flavorings, natural medicines, makeup, incense, household cleaners, and perfumes.
How Do They Affect Humans?
Terpenes affect us on both a physiological and psychological level, and there is research to support this. For example, in 2001, a review of the synergistic effects of terpenes on the body listed many potential uses for terpenes, such as increasing serotonin, dopamine, norepinephrine, and GABA receptor activity.
Although thousands of terpenes are found in nature, very few, have been studied for their specific influence on human biology. The two most commonly studied terpenes are limonene and linalool.
A 2013 study found that an oral dose of a lemon essential oil that contained 70% limonene had antidepressant effects in mice. It was determined that the oil increased dopamine, norepinephrine, and serotonin in various brain regions. Since these endogenous compounds influence our moods, this could explain why it has antidepressant effects.
Linalool, most commonly found in lavender, is known for its sedative, anti-inflammatory, and analgesic effects. It is thought that linalool creates a sedative effect by decreasing sympathetic nerve activity and increasing parasympathetic nerve activity. This helps because the sympathetic nervous system is responsible for our fight-or-flight response. The parasympathetic nervous system opposes this activity by calming a person down and encouraging rest and digestion.
The pain-relieving effects of linalool are a bit more complex. A 2014 study suggested that it influences at least ten pain-related systems in the body. Linalool increases the activity of opioid and dopamine receptors. It is also thought to inhibit the production of inflammatory cytokines, explaining its anti-inflammatory effects.
From a psychological perspective, terpenes affect us way more. A 2003 study found that the aromas a participant liked improved their mood, decreased anxiety, and decreased the unpleasantness of pain, and the ones they disliked worsened those symptoms. In 2004, another study measured the participant’s reactions to the suggested effects of different terpenes. The ones proposed to be relaxing were associated with a decreased heart rate, but when the same compound was said to be stimulating, it increased it. This was true regardless of odor, and it was even true when no odor was used.
Overall, terpenes can help influence our moods, health, and bodily functions while making a product’s smell and taste much more enjoyable.