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If there were one “magic” supplement, that could improve reflux symptoms for most people it would be D-limonene. I have taken orange oil myself occasionally throughout the years with mostly positive effects on my H. pylori upper gut dysbiosis. For example, I contracted the norovirus a few years ago from my son and I thought my H. pylori dysbiosis had returned shortly after. My silent reflux was back, and I had foul-smelling hydrogen sulfide burps. I took two softgels of D-limonene every day for a week, and my dysbiosis resolved itself. My digestion returned to normal. So what is D-limonene and how can it improve your digestive health?

D-limonene, the Most Important Supplement to Relieve Heartburn (GERD)

Limonene is a colorless, cyclic monoterpene that is the major component in citrus fruit peel oil. Limonene takes its name from lemon peels. However, most limonene supplements are obtained from orange peels, either through centrifuge separation or steam distillation. Most limonene is used either as a fragrance for the cosmetic industry or an industrial cleaner. Limonene is also used as flavoring agent in many food products, drinks, and chewing gums. I use D-limonene around the house as a natural botanical insecticide, and it works pretty well keep the outside fire ants from coming into my house (I recommend and use the product Orange Guard). Orange essential oil can be used for aromatherapy (I do not recommend its use around pets or young children it may irritate their lungs), can be taken internally when mixed with a carrier oil (like coconut oil), and topically. Lucky for us, limonene has many health benefits associated with its use.

A chemist, Joe S. Wilkins from Texas suffered from GERD (gastroesophageal reflux disease) for years and searched for alternative treatments. He was working with orange oil trying to formulate natural cleaning products, and he accidentally consumed some of the limonene that was left on his hands.1 After drinking the D-limonene, he noticed that his heartburn was gone and his esophageal inflammation was relieved. D-limonene is an extract from orange peel, which has extremely low toxicity in humans,2 and is GRAS (Generally Recognized as Safe)3 as a food additive and supplement. The daily intake of just one 1000 mg soft gel of orange oil every other day for twenty days has been shown to reduce or eliminate GERD symptoms in most people for six months or longer.4

Orange oil is lighter than water,5 so it floats to the surface of gastric juices in the stomach. When someone is refluxing, orange oil coats the esophagus, protects the esophagus from acid and gastrin, reduces inflammation, and helps heal erosions.6 D-limonene also increases vasoactive intestinal peptide production which promotes proper motility, secretion of bicarbonate and water into pancreatic juice, stimulation of bile production, regulates stomach acidification by regulating pepsinogen and gastrin production, and helps limit osmolarity in the intestines (prevention of diarrhea). VIP is also anti-inflammatory, realigns a stressed circadian rhythm, reduces anxiety, and has antimicrobial properties. D-limonene also increases gastric emptying, improves stage 2 liver detoxification, increases cellular glutathione production if needed, and increases bile production and release.7 8

So how does D-limonene improve reflux and stomach trouble? Orange oil, when burped up, coats the esophagus, protecting the esophagus against caustic contents that would have otherwise been regurgitated from the stomach. D-limonene may stimulate quicker gastric emptying, so less gastric acid, bile, pepsin, and endotoxins remain in the stomach to be refluxed.9 By increasing gastric emptying time, orange oil also reduces fermentation in the stomach and the duodenum, relieving bloating and gastric pressure, reducing reflux. Finally, D-limonene might inhibit Gram-negative upper gut bacterial overgrowth like H. pylori and Provetella, leading to a reduction in endotoxin inflammation and reflux, reducing inflammation in the duodenum, stomach, and esophagus. D-limonene might also help improve the stomach mucosal lining and promote the healing of ulcerated tissue. Finally, D-limonene increases the activity of macrophages (white blood cells that eat microbes to eliminate them from the body), which may help people suffering from dysbiosis by improving their immune function.10

Finally, one interesting fact I discovered about D-limonene and the digestive system is that it was studied in Japan to be used to dissolve gallstones, in people with gallbladder disease. D-limonene was injected into the billary system of about two hundred patients to dissolve their gallstones to prevent the need for gallbladder removal. Gallstones dissolved completely in the gallbladder in about half of the cases (ninety six) and was ineffective in about twenty-five percent of the cases (fifty-nine). The rest of the cases in the study had partial dissolution. I believe that more studies need to be performed to see if we can use this method to safely preserve the gallbladder instead of having it removed if it is full of stones and causing blockage.

Other Positive Health Effects of D-limonene Outside of the Digestive Tract

D-limonene has strong systemic antiviral effects against the virus family Herpesviridae (may help against Herpes Simplex 1, Herpes Simplex 2, and Varicella [chickenpox, shingles] reactivation). “These results suggest that the investigated drugs directly inhibit herpes virus infection and might interfere with virion envelope structures or mask viral structures which are necessary for adsorption or entry into host cells. The inhibition of HSV by the tested monoterpenes appears to occur before adsorption but not after penetration of the virus into the cell. It remains to be determined whether the inhibitory effect of compounds is due to binding of the compounds to viral proteins involved in host cell adsorption and penetration. De Logu et al reported an inactivation of herpesviruses and prevention of cell to cell spread by Santolina insularis essential oil. However, no antiviral effect was observed during the intracellular replication phase, which is in accordance to our results for monoterpenes. Isoborneol, a monoterpene and a component of several plant essential oils, showed virucidal activity against HSV-1 and specifically inhibited glycosylation of viral proteins. The application of the monoterpene cineole protected mice against infection with HSV-2. Since, essential oils are able to inhibit acyclovir-resistant HSV-1 isolates, the mechanism of interaction between essential oils and these compounds and acyclovir with HSV must be different. Acyclovir inhibits virus replication by interference with the DNA polymerase inside the cell, whereas monoterpenes probably inactivate HSV before it enters the cell. Astani et al. also showed high antiviral activity for essential oils and isolated monoterpenes when herpesvirus was incubated with these drugs prior to host cell infection. Viral resistance to acyclovir represents a particular problem; the prevalence of resistance in acyclovir-treated immunocompromised individuals is approximately 4 to 7%.” Orange essential oil also provides pain relief and accelerates healing when it is applied to canker and cold sores. I recommend using a natural orange flavored lip balm when you are suffering from cold sores.11 12

Limonene has shown sedative properties, which may help those with anxiety disorders. Limonene increases GABA(gamma-Aminobutyric acid) production in the brain (by its metabolites perillic acid and perillyl alcohol activating the GABAA cellular receptors), reduces glutamate excitability, and may prevent neurotransmitter (serotonin, dopamine, and norepinephrine) overproduction (which may improve mood, reduce anxiety, and improve brain fog). Limonene is also shown to have anti-seizure properties, more than likely from its ability to reduce glutamic acid neuronal over-excitability. Limonene binds to and activates the adenosine A2A receptor which helps to regulate glutamate, GABA, and dopamine release. Finally, limonene has been found to reduce stress hormone cortisol serum levels, improving adrenal fatigue in people with elevated cortisol.13 14 15

Research has also shown that D-limonene might also have anti-cancer properties. Limonene prevents the growth of cancer cells by inhibiting growth controlling G proteins (guanine nucleotide-binding protein, inhibits mainly p21ras), that is signal transducing molecules that induce cell growth. Limonene inhibits posttranslational addition of hydrophobic groups to the G protein peptide precursor, which is necessary for the growth controlling G proteins to function properly, therefore eliminating cancerous cells by reducing growth and replication. Limonene reduces breast cancer growth by inhibiting the expression of cyclin D1 and IL-6. Cyclin D1 speeds up cellular progression, allowing cancer cells to proliferate faster. Finally, in stomach cancer cells, limonene decreased BCL2 (B-cell lymphoma 2 gene), increased p53 (tumor protein 53 suppressor gene), decreases VEGF (Vascular endothelial growth factor, tumor’s ability to receive blood flow), reduced H. pylori, and reduced inflammation (inhibits the inflammation inducers TNF-α and NF-κB) inhibiting cancer growth and inducing cancer cell apoptosis.16 17 18 19

Potential Side Effects of Limonene Use

I do caution the use of D-limonene in people with an elevated Th2 immune system (histamine intolerance or mast cell activation disorder) or individuals with severe gastritis, and it may make them worse. Orange oil can also be sedating for some people if so take it with dinner instead of breakfast if it makes you sleepy or sluggish. Limonene used in topical products has rarely been shown to cause dermatitis potentially. Other rare side effects of orange oil supplementation are increased esophageal inflammation, aspiration, and breathing issues.20 21

My Recommended Brand of Limonene

I recommend that you either use the limonene supplement Orange Burps, in easy to swallow softgels. In addition, be sure to follow the supplement instructions as well. Most people take limonene with a meal to prevent gastrointestinal upset. I recommend most people take one to two capsules in the morning with breakfast, but if the supplement becomes too sedating you can take it with dinner. Orange oil is very important for protecting the esophagus and stomach, relieving inflammation in the digestive system, and reducing and preventing dysbiosis. I recommend trying it if you are dealing with heartburn today and find some relief.