Limonene is one of hundreds of constituents found in essential oils. As an individual compound, or as part of a “whole” essential oil, it provides numerous health benefits which have helped bring attention to the therapeutic benefits of the oils themselves.
In this article, I’ll cover some of those health benefits, as well as explain where to find limonene and how to determine how much you get if you use essential oils.
While essential oils provide a plethora of health benefits when used as a “whole” essential oil, it’s sometimes easier to understand how the individual compounds affect our health. That’s just how nutrition science and research works.
For example, we know that animal-based proteins like steak, bison, and whey are an important part of a healthy, high-protein diet, because researchers have studied the effects of the essential amino acids, creatine monohydrate, and other nutrients found in those foods. However, that doesn’t mean you should only eat the amino acids and creatine. Animal protein contains many other compounds that enhance health, which is why you eat the whole food and supplement your diet with creatine, amino acids, omega-3s, and other micronutrient, botanicals, and ergogenic compounds.
It’s the same thing with essential oils. While there could be some benefit to supplementing with limonene alone, there’s also plenty of evidence to show why using the whole essential oil would be better.
With all that said, let’s get to the topic of today’s article: d-limonene.
What is d-Limonene?
Though it’s found in another isomer form, r-limonene, the more prevalent and studied form is d-limonene. For readability, I simply use limonene in this article, with the understanding I’m referring to d-limonene.
d-limonene is one of the most common terpenes found in nature. But, what the heck is a terpene? A terpene a class of volatile compounds commonly made by coniferous trees and citrus fruits. Because of their volatility, they quickly dissipate when exposed to the air, which is why you don’t find them in dried herbs. Terpenes have a strong odor designed to ward off pests in plants, and are used medicinally and supplementally. Limonene is one of those terpenes, and based on the name of it, you might (accurately) guess that it smells like somewhat like lemon.
Where Do You Get Limonene?
Though you’re not getting therapeutic doses, you’re probably consuming more limonene than you realize. It’s used as a fragrance and flavor in a number of foods, such as candy, gum, soft drinks, ice cream, and (hopefully you don’t drink it, but…) fruit juice.
Aside from food and dietary supplements, limonene is also used as a healthier cleaning substance in household products, manufacturing, and industrial printing, as a degreaser for metals, and in paint as a solvent. You’ll also see limonene on the label of shampoos, soaps, fragrances, and other personal care products.
The most abundant sources of limonene are the peels of citrus fruits (which is where the essential oils are derived), dill, caraway, fennel, celery, and turpentine, not that you should consume turpentine.
For commercial and industrial use, most limonene comes from orange essential oil.
The table below outlines some of the most concentrated sources of limonene.
|Bergamot (Citrus bergamia)||40%|
|Bitter Orange (citrus aurantium)||97%|
|Elemi (Canarium luzonicum)||42%|
|Grapefruit (Citrus paradisii)||93%|
|Lemon (Citrus limon)||53%|
|Orange (Citrus sinuses)||93%|
|Pomelo (Citrus grandis)||75%|
The body metabolizes limonene quickly, and within 24 hours, clears almost all of the limonene from a single dose.
Health Benefits of D-Limonene
The health benefits of limonene described below are connected to the internal use, or consumption of limonene. Though the inhalation of limonene-containing essential oils causes numerous physiological effects, the FDA at this point does not allow health claims to be connected to the inhalation of essential oils.
Interestingly, there’s also some evidence that limonene could enhance the effects of certain cannabinoids as well. I would expect to see more research on this as cannabis gets legalized, making it easier to conduct comprehensive research studies.
Limonene enhances skin health:* When studied as limonene alone, or as the main constituent in certain essential oils, limonene has been shown to support skin health and healing, and normal inflammatory levels of the skin.*
Limonene supports kidney function:* Animal research shows limonene supports healthy kidney function, probably by supporting normal inflammation levels or acting as an antioxidant.
Limonene provides antioxidant benefits:* Limonene itself acts as an antioxidant, and also seems to support production of glutathione, the body’s main antioxidant.*
In one interesting study, diabetic rats were given limonene for 45 days and their blood, kidney, and liver function was compared to rats who didn’t get limonene. Glutathione production and activity, as well as vitamin C activity, increased in those who got the limonene.
Reactive oxygen species (ROS) cause oxidation in the body. Some oxidation is inevitable, but in those with diabetes, oxidation is higher than normal, and contributes to many of the complications related to the disease. The antioxidant effect of limonene could be helpful in slowing the progression of health problems for diabetics.
Oxidation and inflammation contribute to neuropathy, arteriosclerosis, and retinopathy, so something like limonene could slow the progression toward those problems. Of course, it isn’t a cure, and won’t have the same effect as cutting carbs or following a ketogenic diet would.
Limonene supports normal inflammation levels:* Limonene supports normal inflammatory levels in a number of different cases, including those with osteoarthritis.
Limonene supports digestive system health:* Researchers caused gastric ulcers in rats by…check this out…giving them alcohol and non-steroidal anti-inflammatory drugs…how many people drink alcohol and regularly take NSAIDs for pain, and then end up on an anti-ulcer medication without understanding the NSAIDs for pain contribute to the ulcers in the first place?
Anyway, the rats that got either limonene, or Citrus aurantium essential oil while getting the alcohol and NSAIDs almost totally avoided the ulcers. It turns out that the limonene increases gastric mucus, which supports the health of the lining of the stomach.
Limonene also supports the health of the digestive system by supporting normal inflammatory levels of the gut lining, which could help relieve symptoms of digestive issues such as colitis (Note: “relieving symptoms” is not the same as curing colitis. Getting rid of colitis requires a diet and lifestyle change).
Limonene supports respiratory function:* Internal use of limonene was shown to lessen the occurrence of asthma by supporting normal inflammatory levels and helping to reduce bronchoconstriction.
Limonene supports healthy lipid and glucose levels, and improved body composition:* In an animal study, researchers tried to make rats fat by changing their diet. The group of rats who also received limonene had healthier lipid, glucose, liver enzyme, and body composition levels. The development of non-alcoholic fatty liver disease (NAFLD) was less in the rats who received limonene as well.
Bodybuilders and physique competitors often eat grapefruit to enhance fat metabolism, but there’s very little limonene in the fruit or fruit juice. It is found in the rind or peel, which is why it would be better to supplement with grapefruit essential oil to support fat metabolism, than it would to eat grapefruit.*
How much limonene is used for therapeutic effects?
When used in supplements, 1 gram of limonene is a pretty standard dose. You can order supplements with pure limonene, or use essential oils as dietary supplements.
To determine the amount of limonene in essential oils, you have to do some math to figure out how much you actually get.
When measuring water, 1 fluid ounce equals 29.57 grams of water. So, using orange essential oil as an example, which is 93% limonene, 1 fluid ounce equals 27.5 grams (93% x 29.57), right? Not quite.
Water is more dense than orange essential oil, which is why, when you add it to your water bottle, it floats to the top. That means that it has a specific gravity of less than 1.0. Do you remember specific gravity from high school science, or did you sleep through that lesson?
The specific gravity of orange essential oil is .84, so now, we need to take that 27.5 grams and multiply it by .84. That leaves us with 23.1 grams of limonene in 1 fluid ounce of orange essential oil. A 15-ml bottle is 0.5 ounce, so it would have 13.75 grams of limonene.
Of course, most essential oils users measure their oils in “drops,” not ounces or grams. Again, there’s some variance in the size of a drop, based on the viscosity of the oil and the size of the hole in the bottle. On average a 15-ml bottle of essential oil has 280-300 drops. So, if you assumed there were 300 drops in a bottle, you’d need about 22 drops to get 1 gram of limonene from orange essential oil.
And with all that said, there’s always some variance in the amount of limonene in an essential oil, based on how the plant is grown and how the oils are extracted.
The way I look at it is this: If your goal is to improve overall health, and the amount you consume varies a bit, you’ll be alright. You’re also getting numerous other health-promoting compounds that I’ll cover in other articles.
And if you’re still wigging out because you’re a super-rigid, analytical-minded person, take some limonene right now. It’s also good for calming the mind.* And this is coming from a guy who measures out his coffee beans each morning on a food scale.