Limonene is one of the most potent aromatic chemicals in marijuana, though it’s mostly known as a major component of oranges, lemons and other citrus fruits. Limonene is part of a class of molecules in the cannabis plant called terpenes, which give the plant’s buds their pungent smell and distinctive taste. Aside from making your weed more pleasant to smoke, limonene is also a potential cancer fighter.
Terpenes are important not just for the aesthetic of marijuana products. Terpenes like limonene and more than a dozen others interact with marijuana’s main psychoactive ingredient, Delta-9 tetrahydrocannabinol (THC), and its other potent cannabinoid, cannabidiol (CBD). Terpenes temper and enhance the effect of these central cannabinoid molecules and others to produce what researchers know as the “entourage effect.”
Though poorly understood, the entourage effect has been documented over and over again in clinical research. In a variety of scenarios in which whole cannabis and its extracts have been compared to isolated cannabinoids, the entourage effect has helped cut side effects drastically and improve outcomes.
Limonene, as the name implies, is a chemical that comes mostly from orange, lemon, lime and other citrus fruits — typically distilled from the peels. The resulting pure chemical is used commonly as a flavoring agent and solvent and fragrance in household cleaners. It is mostly non-toxic, but concentrated fumes can inflame the airways. Skin exposure to the concentrated form of the terpene can cause irritation.
Limonene as medicine
Properly administered as a medicine, however, limonene has been shown to slow down tumor formation in rats. It also seemed to help a little in reducing tumor activity in a few patients with breast and colon cancer, but the study was tiny and therefore not very useful.
More promising is this terpene’s ability to cut back skin tumors in rats, and reduce tumor activity in the gastrointestinal tract. The terpene also reduces inflammation and pain when administered to rats and humans.
“D-limonene has well-established chemopreventive activity against many types of cancer,” according to a study in the journal Alternative Medicine Review (AMR).
PubChem, the U.S. government’s clearinghouse of information on nearly all pharmaceuticals and industrial chemicals in use, also acknowledges it’s cancer-fighting properties.
“Limonene is one of the active components of dietary phytochemicals that appears to be protective against cancer,” states the PubChem summary.
Also, some studies show that high dietary concentrations of limonene actually help lower cholesterol in your bloodstream because of its solvent effect on the fatty substance. Arterial cholesterol buildup causes all sorts of congestive heart and cardiovascular disease.
Limonene may also help with conditions with symptoms related to acid reflux.:
“Because of its gastric acid neutralizing effect and its support of normal peristalsis, it has also been used for relief of heartburn and gastroesophageal reflux (GERD),” according to AMR.
All these documented effects are promising, but this particular terpene has at least one medical use that’s been established for years. If you have gallstones — typically formed from cholesterol — surgeons may inject limonene into your gallbladder to dissolve them.
An odd side note: this cancer-fighting terpene can, in high enough doses, actually causes kidney tumors, but exclusively in male rats. Later studies confirmed it has no mutagenic or other cancer-causing effect in humans.
Additional Limonene References:
D-Limonene modulates inflammation, oxidative stress and Ras-ERK pathway to inhibit murine skin tumorigenesis.
Chaudhary SC1, Siddiqui MS, Athar M, Alam MS.
Human Experimental Toxicology
Physio-pharmacological Investigations About the Anti-inflammatory and Antinociceptive Efficacy of (+)-Limonene Epoxide
Antonia Amanda Cardoso de Almeida et al