What to Know About Limonene
Medically reviewed by Elizabeth Barnes, RDN
Limonene is a chemical found in fruits from the genus Citrus. It is a terpene and is abundant in the peels and essential oils of oranges, lemons, mandarins, and other citrus fruits.
Limonene comes in two forms, D-limonene and L-limonene, which have a pleasant lemon-like aroma. Due to its smell, limonene is commonly used in fragrances, soaps, shampoos, and other health and cosmetic items. It is also used as a flavoring agent in food products.
There are many potential health benefits of limonene. Research has been conducted on how using limonene may benefit various health conditions, including ulcerative colitis (UC), viral illnesses, and even cancer. However, there is little scientific evidence to support these and other claims.
This article will look at the science behind some of the potential benefits of limonene. It will also cover safety considerations, interactions, dosage, and sources of limonene.
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What Is Limonene Used For?
Explainer
Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.
Aside from its household uses, limonene may have some health benefits.
Research on limonene has increased in recent years. However, most studies on limonene's health benefits have been performed on animals or in lab settings. Very few human studies exist, which means there is still much to learn about how limonene may work in different people.
Through research, it's become apparent that limonene has several properties that may benefit human health. Some of these are outlined below.
Antioxidant and Anti-Inflammatory Activity
As a terpene, limonene contains chemical substances with known antioxidant and anti-inflammatory activity. Anti-inflammatory substances can help reduce inflammation in the body, while antioxidants help prevent and reduce cell damage.
Due to these properties, limonene has been looked into for its possible effects on health conditions such as neurodegenerative diseases. In vitro research shows that limonene's antioxidant and anti-inflammatory activities may protect your brain from damage and certain diseases.
In an animal study, limonene was found to reduce inflammation in a rat with ulcerative colitis. Limonene supplementation was associated with decreases in both inflammatory biomarkers and intestinal damage in the rats with UC due to limonene's antioxidant and anti-inflammatory actions.
It's important that more research be carried out in this area,however. Human trials are necessary to learn how limonene supplementation may reduce inflammation and prevent cell damage in humans.
Anticancer Potential
Some people with cancer choose to use various dietary supplements as complementary treatments to chemotherapy, radiation, and other cancer treatments. Limonene has been studied for its potential anticancer properties.
According to one review, limonene has been found to alter signaling pathways, increase cancer cell death, and inhibit metastasis in several in vitro (outside of a living organism) and in vivo (animal) studies.
In animal studies, limonene has been shown to reduce factors like tumor size and the number of tumors. This has led some researchers to believe that limonene may increase survival in rodents with cancer. However, it's unknown if these results would be duplicated in humans.
A small number of human studies on limonene's role in breast cancer have been conducted. In these studies, limonene supplementation has yet to be found to produce significant benefits in humans with cancer. For the most part, though, human studies on this subject have been very small and of poor design, so more research is needed.
Antiviral Properties
There is some evidence that limonene may have a role in the treatment of viruses like the flu, COVID-19, and herpesvirus.
A laboratory study found that both L- and D-limonene act as a disinfectant against influenza A virus H1N1. Limonene was found to be the major component in the essential oil from orange peels and responsible for the antiviral properties displayed in the study.
Other lab research has suggested that limonene has antiviral properties against COVID-19, although much more research is needed.
Limonene has also been found to have a potential role in treating human herpesvirus. In an in vivo study, limonene was shown to directly inhibit herpesvirus. Limonene was most effective when added to cells just before herpes virus infection.
Research on the role of limonene as an antiviral agent is in the very early stages. More research must be conducted to determine if limonene can in fact treat or prevent any viruses in humans.
Heart Protection
Animal experiments have revealed a potential role of limonene in heart health.
In one study, rats with induced cardiac (heart) toxicity received varying doses of oral limonene for three weeks. Compared to control groups, rats who received 200 milligrams per kilogram of body weight (mg/kg) of limonene had significant improvements in altered total cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol. Limonene supplementation was also found to reverse changes in inflammatory markers and, thus, cardiac toxicity risk.
In another animal study, researchers induced myocardial infarctions (heart attacks) in rats. The rats then took limonene at a dose of 1 mg/kg 30 minutes after the induced heart attacks. Limonene was found to reduce the size and intensity of possible heart injuries in the rats.
Despite these positive findings, it is essential that more research be conducted, especially in humans, to determine if limonene does indeed have a role in heart health.
Safety Considerations
Limonene is generally regarded as safe to use in cosmetics, cleaning products, and dietary supplements. It is also thought to have a low risk of toxicity. However, there is an overall lack of safety information available for limonene, mostly due to the lack of human trials.
There have been some reports of side effects associated with limonene use in a small number of studies on people with cancer. According to the research, possible side effects of limonene include:
Skin irritation has also been reported as a result of using topical limonene.
While limonene may be safe for most people, some may need to avoid it.
At this time, there isn't enough research on the safety of limonene in people who are pregnant or breastfeeding, or in children.
One animal study concluded that limonene supplementation may increase contractions of the uterus during pregnancy, but this hasn't been confirmed in humans. While limonene in amounts found in foods may be safe, it's recommended that people who are pregnant or breastfeeding avoid using limonene supplements.
Other people may need to avoid using limonene. It's best to talk with a healthcare provider before starting a new supplement, especially if you have any health conditions or use any prescription medications.
Interactions
Limonene supplements may interact with other supplements or medications. Interactions may cause a medication or supplement to increase or decrease its effectiveness, which can be dangerous in some cases.
However, there is no solid evidence of possible interactions between limonene and other supplements, medications, herbs, or foods.
Regardless, interactions may still exist, and more research should be done to find possible interactions for limonene.
Until more research is available, talk with a healthcare provider and disclose all the medications, supplements, and herbs you take to learn if any may interact.
Dosage: How Much Limonene Should I Take?
Limonene dosage can vary and may depend on the product or the reason for use. Due to the limited available research, there isn't a consensus on safe and proper dosage for limonene supplements.
It may be necessary to start with a low dose of limonene and slowly work your way up to the recommended dose. Doing so may reduce your risk of experiencing side effects when using limonene for the first time.
Unless otherwise directed by a healthcare provider, it's recommended that you follow the dosage directions listed on the supplement label or packaging. Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.
Sources of Limonene & What to Look For
You can consume limonene through foods or supplements.
While some foods contain natural sources of limonene, others are flavored with it. However, foods tend to contain much smaller amounts of limonene than supplements.
Food Sources
Limonene is a chemical naturally found in the rinds of fruits from the citrus family. These fruits include oranges, lemons, and limes. Essential oils taken from the rinds of these fruits also contain limonene.
Due to its pleasant smell and taste, limonene is also sometimes added to fruit juices, candies, chewing gums, drinks, and ice creams.
Because it is not widely found in foods, many people choose to use limonene in supplement form.
Limonene Supplements
Like most dietary supplements, limonene supplements can be purchased online or in certain stores, including grocery stores and some retail chains.
Limonene supplements are commonly sold as soft gels, capsules, and liquid extracts. You can find supplements that contain only limonene, but some supplements contain limonene in addition to other substances (like nutrients, herbs, and essential oils).
Limonene is naturally vegan and gluten-free. Keep in mind, though, that some supplement capsules are made from gelatin, which is not a vegan product. Certain products that contain limonene may also be organic.
Explainer
Dietary supplements are not regulated the same way drugs are in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement tested by a trusted third party, such as USP, ConsumerLab.com, or NSF.org.
However, even if supplements are third-party tested, they may not be safe for all or effective in general. Therefore, it is important to talk to a healthcare provider about any supplements you plan to take.
Summary
Limonene is a chemical substance found in the peels and essential oils of citrus fruits. They may offer health benefits. However, most of the available research on limonene has been performed in labs or on animal subjects. It is essential that more human trials be conducted to prove the health claims surrounding limonene.
If you’re thinking of using limonene supplements, talk with a healthcare provider about how to safely get started.
Frequently Asked Questions
Does limonene reduce estrogen?
Limonene has not been shown to directly reduce estrogen. However, one of its metabolites, perillyl alcohol, has been found to suppress the growth of tumors in estrogen-receptor breast cancer cells in laboratory research.
Overall, there is no strong evidence that limonene or its metabolites reduce estrogen levels.
Who should not take limonene?
Limonene may not be safe for everyone to take.
There isn’t solid evidence that limonene supplements are safe to use by people who are pregnant or breastfeeding. People with a citrus allergy should also avoid limonene.
People with certain health conditions or who take prescription medications may also need to avoid limonene. Play it safe and talk with a healthcare provider before using limonene.
Is D-limonene the same thing as limonene?
Although the terms “limonene” and “D-limonene” are often used interchangeably, there are two forms of limonene: D-limonene and L-limonene. These forms are considered enantiomers, meaning they have the same chemical structures but as mirror images and cannot be superimposed. D-limonene is the form most often used in supplements and foods.
Is limonene a carcinogen?
No. There is no evidence that limonene is a carcinogen. In fact, the opposite may be true. Research points to limonene as a substance with potential anticancer properties. Although more studies are needed, some results have shown an insignificant positive effect of limonene on tumor progression and growth in certain breast cancers.
Read the original article on Verywell Health.
