I first made reference to limonene in my post The benefits of citrus essential oils. There have been more than a few studies carried out on the anti-cancer properties of limonene. That it’s not being actively used in the treatment of cancer is, in my opinion, a likely testament to the profit-driven nature of modern medicine.
You see, limonene is a compound found in abundance in the essential oils of citrus fruits. In fact, the essential oils of grapefruit, orange and tangerine have more than 90 per cent limonene. I can’t see pharmaceutical manufacturers making a fortune out of something they can’t patent.
In order to understand how and why limonene works, we first need to understand a little of the process by which cancer develops in the body.
Three phases of cancer cells
Mutation – According to Bruce Ames of the University of California, human cells are attacked by free radicals 10,000 times a day. Eventually, a free radical attack can result in a DNA mutation of a cell, which turns it into a cancerous cell. Now, the body has a system in place to deal with this called Apoptosis, where basically all cells, normal or mutated, have a “use by date”. Upon reaching this point in time, a cell is programmed to self-terminate. Where the problem starts is where a mutated cell over-rides this programme and so is able to divide and grow endlessly.
Progression – In the progression (or promotion) stage, proteins called farnsyl groups embed in the outer cell wall, preventing cell-to-cell communication. Cells begin to multiply out of control. This is when you have the beginnings of a tumour or growth.
Metastasis – In the final phase, cancer cells no longer remain localised to a tumour. They enter blood vessels and lymph nodes, creating
new growths throughout the body. As the cancer progresses, the body is being literally eaten alive with cancer cells.
Limonene and its actions in all phases of cancer
There have been numerous animal and human studies showing limonene to be effective against cancer in all three stages. Studies in 1971 and 1976 showed that limonene was able to inhibit the initiation phase of skin cancer. This was confirmed by later studies in 1983-1984, 1988, 1989 and 1991. A study in 1998 was able to show that limonene inhibited the formation of cancer by increasing the levels of what are known as phase 11 liver enyzymes; these enzymes bind a whole range of carcinogens and allow them to be easily eliminated from the digestive and respiratory systems.
What about the progression/promotion stage of cancer? A study in 1992 found that limonene prevented the famesyl proteins from attaching to the surface of the mutated cell (these proteins, you will remember, prevent cell-to-cell communication), as well as allowing the mutated molecule to exit the cell and be destroyed.
And, as for the final phase of cancer, trials conducted on rats in 1986 found an 80 per cent regression in mammary tumours through the use of limonene. This was later confirmed by further studies in 1992, 1993 and 1994.
Works with rats, what about humans?
Most of the studies I’ve mentioned, up to now, were conducted with rats. Would limonene work with humans? In 1994, a team from the University of Wisconsin carried out a study to compare the human metabolism of limonene with that of rats. The study concluded that the rat metabolism of limonene was very similar to that of humans, which suggests that limonene would benefit humans. And, in 1998, a study to research the effect of limonene on human cancer patients was first carried out in London with promising results. Researchers achieved close to a 15 per cent remission rate in advanced colon cancer and breast cancer patients with doses of 1-15 grams of limonene. In some cases patients with weeks to live had their lives extended by around 18 months.
The indications are that limonene works better as a preventative, and in the early stages of cancer. In clinical trials, frankincense is shown to be the greater inhibitor of cancer.* It is, however, easier to put essential oils such as tangerine, grapefruit and orange to use in your diet than frankincense. The simplest way is to add 4-5 drops of oil to a bottle of water and drink. It makes a great alternative to the soft drinks and junk beverages we have marketed to us (see my post Essential oils for the summer for ideas on how you can incorporate these oils into your beverages).
If you check out our site you will further information on the studies carried out between 1971 and 2013.
Till next time!
Disclaimer: Please remember that anything discussed here does not constitute medical advice and cannot substitute for appropriate medical care. Where essential oils are mentioned, it’s recommended you use only pure, unadulterated therapeutic grade essential oils and follow the safety directions of the manufacturer.
*Essential oils desk reference (5th edition), Life Science Publishing, 2011