What is Limonene?

What is Limonene?

Limonene is a terpene that also goes by the names ᴅ-limonene and ʟ-limonene. Terpenes are aromatic compounds found in hundreds of foods and plant species (including Cannabis sativa). ᴅ-limonene is one of the most common terpenes in nature thanks to its prevalence in the essential oils of citrus fruits. Once isolated, limonene is used in perfumes, cleaners, and as a flavouring agent for food.

While limonene is often assumed to be abundant in strains that smell like lemon, this isn’t always the case. When seeking strains high in limonene, you’ll need to find lab-tested products to know that the strain you’re buying is in fact limonene-packed.

Whereas THC typically makes up 10-30% of a flower’s dry weight, limonene occurs in trace amounts, generally less than 2%.

High-limonene cannabis strains

Some strains exhibit higher levels of limonene than others, but these levels can vary widely across harvests depending on genetics, growing techniques, and curing processes. The only way to know if your strain is high in limonene is through lab-tested batches.

According to data from Leafly’s lab partners, these popular strains tend to produce limonene-dominant terpene profiles:

  • Banana OG
  • Berry White
  • Black Cherry Soda
  • Cinex
  • Do-Si-Dos
  • MAC
  • Purple Hindu Kush
  • Quantum Kush
  • Strawberry Banana
  • Tahoe OG
  • Wedding Cake
  • White Fire OG

To find strains containing limonene on Leafly, keep an eye out for strain flowers containing the color yellow. Take White Fire OG as an example of what to look for:

Limonene’s potential effects and benefits

Despite limonene’s potential therapeutic benefits, little is known about how it works in the brain and body, and what doses are required to achieve these benefits. In many of the limonene studies to date, high doses were used—much higher than amounts found in cannabis. More cannabis-focused research is needed, but studies on limonene so far have shown potential in the following applications:

  • Elevated mood
  • Stress relief
  • Antifungal properties
  • Antibacterial properties
  • May help relieve heartburn and gastric reflux
  • Improves absorption of other terpenes and chemicals by way of the skin, mucous membranes, and digestive tract

There’s also promising evidence for limonene’s anti-tumor effects. In lab rodents, limonene inhibited the growth of skin and mammary tumors. These studies were followed up with a Phase I human clinical trial which found that limonene was somewhat effective at reducing breast cancer tumor growth for nearly a year. Later studies found that daily limonene supplementation for 2-6 weeks silenced a protein that promotes breast cancer tumor growth, suggesting that daily limonene consumption may inhibit the growth and spread of breast tumors.

Additional reports have revealed benefits of limonene in laboratory models of lung cancer and brain cancer by causing tumor cell death. But like limonene’s benefits in breast cancer, high doses are likely needed beyond what may be present in cannabis alone. It’s unknown, however, whether the presence of certain cannabinoids extends limonene’s anti-cancer effects. Currently, there is not nearly enough evidence to conclude that cannabis products high in limonene will be effective as cancer treatments in humans.

Future research on limonene

It remains unclear how limonene achieves its therapeutic effects. Inhalation of limonene vapor increases serotonin and dopamine levels in key regions of the brain that are associated with anxiety, depression, and OCD. Does limonene merely stimulate the brain’s olfactory system, or is it directly affecting brain cells themselves? We don’t yet know.

Unlike some of the other terpenes that have well-defined brain targets, such as linalool and b-caryophyllene, limonene’s targets remain unclear.

By better understanding limonene’s targets in the brain and body, scientists may help direct users towards strains or products where limonene’s therapeutic benefits are optimized by a particular cannabinoid and terpene profile.

Dosing considerations for Limonene.

The appropriate dose of limonene depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for limonene. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

Supporting research

What is Limonene?

Despite limonene’s relative chemical stability, studies into its effects are limited. A handful of preclinical studies have been performed. It is suggested that limonene may have anti-inflammatory, antioxidant, and cardioprotective qualities.

The Department of Medicinal Chemistry and Natural Products in Israel conducted an in vitro study using citrus oil in 2006. They concluded that a “mixture of citrus oil and MgCl₂ could be used as a natural antibacterial and anti-inflammatory agent”.

A second in vitro study, this time published by the Journal of Oleo Science, found that limonene inhibited proinflammatory cytokines. Although proinflammatory cytokines are a necessary part of the body’s inflammatory response, a buildup can lead to instances of chronic inflammation. The authors suggest that “ᴅ-limonene may be considered a potential anti-inflammatory candidate”.

Following reports of ᴅ-limonene influencing fat retained by the liver, researchers in China examined the compound using an animal model of high-fat, diet-induced obesity. They concluded that limonene might have uses as a dietary supplement, “preventing and ameliorating metabolic disorders” .

A 2018 review published by the journal Experimental and Therapeutic Medicine observed the impact of ᴅ-limonene on “stroke-prone spontaneously hypertensive rats” (SHRsp). ᴅ-limonene was found to decrease the “systolic blood pressure of SHRsp rats following stroke” while protecting against memory and cognitive impairment .

Safety and side effects

Limonene has been approved as a safe food additive and flavouring by the Food and Drug Administration since 1994. When assessing the toxicity of the compound, they found that it has “relatively low acute toxicity taken orally”. The only reported side effect was the risk of skin irritation after using limonene-infused shampoos, creams, or sprays.

Limonene cannabis strains for anxiety, depression, and stress relief.

Limonene is the second most common terpene in nature and a prominent terpene in cannabis. The fragrance of citrus fruit peels is comprised mostly of limonene, so you’d be correct to assume that this terpene takes its name from the lemon. Limonene’s pleasant odor has made it a common additive in perfumes and food.

Limonene can be safely consumed in high, naturally-occurring, amounts. However, adverse effects may be felt at doses around one gram per kilogram of body weight (around 68 grams of limonene for a 150-pound person). While this is significantly higher than what you’d find in cannabis flower or cannabis products, limonene extract can be purchased as a dietary supplement, so it’s advised that you consult a physician before adding substantial amounts of limonene to your diet.

Limonene is formed from geranyl pyrophosphate, the precursor to the cannabinoids. Once limonene is produced, it either stays in cannabis as limonene or gets converted to the other cannabis terpenes.

As with many terpenes, plants produce limonene to help protect them against harmful microbes, and its antibacterial and antioxidant effects have been well-documented. But beyond its abilities to protect the plant, it also has an impact on brain function that scientists are working to better understand for the treatment of a variety of ailments—namely anxiety and other mental health disorders.

The potential benefits of limonene on anxiety, depression, and stress

Studies have found that both orally consumed limonene and inhaled limonene vapor reduces anxiety in lab mice. Similarly, limonene also reduced obsessive compulsive disorder-like behavior (OCD). However, limonene’s effectiveness seems to depend on mouse strain or type of anxiety test administered, perhaps indicating that its anxiety-reducing effects may work in some but not others.

Limonene may also have antidepressant qualities. Few human studies have been conducted on limonene’s antidepressant effects, but one small study of 12 hospitalized patients with depression revealed promising results. Limonene vapor inhalation reduced the need for antidepressant medication in 9 of the patients, normalized stress hormone levels, and improved immune function.

It remains unclear how limonene achieves these therapeutic effects. Inhalation of limonene vapor increases serotonin and dopamine levels in key regions of the brain that are associated with anxiety, depression, and OCD. At this point, it’s unclear how limonene boosts these brain chemical levels. Does limonene merely stimulate the brain’s olfactory system, or is it directly affecting brain cells, themselves? The actual mechanism is an area for future research, but it’s likely some combination of both stimulating the olfactory system and direct cellular action.

Limonene give strains a lemon aroma

The aroma that characterizes a strain is not due to one terpene, but rather a combination of all the terpenes that it contains. One terpene in isolation will have a very different aroma from many terpenes present in combination, even if that combination contains a lot of one terpene.

You can experience this first hand in certain dispensaries, many of which contain “terpene stations” that allow you to smell the aroma of individual terpenes. None of these smells all that much like cannabis flower, and the reason is that cannabis doesn’t contain just one terpene—it contains many.

Knowing the name and even smelling the aroma of a strain may not be enough to tell you what it’s specific terpene profile is. The only way to know for sure what the terpene profile of a cannabis strain or product is is to have accurate lab testing results.

Unfortunately, most states do not require cannabis products to get tested for terpene levels, and most brands do not provide this information on product labels.

However, there are some cannabis brands that provide terpene profiles to consumers on product labels, and some retail locations are starting to carry these products more. If you’re interested in knowing the terpene profile of strain, ask your budtender if they carry any products with lab tested terpene profiles on the label.

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