Oregano (Origanum vulgare) is a perennial herb indigenous to Europe, Asia, and particularly the Mediterranean. It is a member of the mint family and is closely related to marjoram. The primary active medical ingredient in oregano is carvacrol, which has its highest concentration in the oil from oregano plants of the Mediterranean.
Oregano has been used since ancient times to treat medical ailments, Wikipedia reports that Hippocrates used oregano as an antiseptic, as well as a cure for stomach and respiratory ailments.
Several scientific studies have been published that have investigated oregano and carvacrol. Most of the studies report research that was done on animals or cell lines, but there are a few that researched directly in humans. What follows is a short but representative review of the literature.
Oregano Oil Treats Intestinal Parasites
This first study found that the administration of oregano oil (oreganum vulgare) consumed orally for 6 weeks was effective at curing enteric (intestinal) parasite infections in humans. Fourteen participants were used in this study all of whom tested positive for the enteric parasites Blastocystis hominis, Entamoeba hartmanni, and Endolimax nana. The authors report that: “there was complete disappearance of Entamoeba hartmanni (four cases), Endolimax nana (one case), and Blastocystis hominis (eight cases). Also, Blastocystis hominis scores declined in three additional cases. Gastrointestinal symptoms improved in seven of the 11 patients who had tested positive for Blastocystis hominis.”
This paper is important because it establishes the antiparasitic properties of oregano in humans.
1. Inhibition of enteric parasites by emulsified oil of oregano in vivo.
Force M, Sparks WS, Ronzio RA.
Phytother Res., 2000 May, 14(3), 213-214.
Oregano Oil Kills Microorganisms in the Laboratory
The next paper is not in human study, but it does establish that oregano oil is effective at killing microorganisms. The authors experimented in the lab with several essential oils, to see how effective they were against a wide variety of bacteria, molds, and yeasts, and found that “of the tested compounds, cinnamaldehyde, thymol, and carvacrol showed the strongest antimicrobial effectiveness”.
2. Vapor-phase activities of cinnamon, thyme, and oregano essential oils and key constituents against foodborne microorganisms.
López P, Sanchez C, Batlle R, Nerín C.
J Agric Food Chem., 2007 May 30, 55(11), 4348-4356.
Oregano Oil Cures Fatal Yeast (Candida) Infections in Mice
Oregano oil kills yeast (Candida albicans), and when mice were infected with 5 times the lethal dose of the infectious Candida yeast, 80% of them survived.
3. Antifungal activities of origanum oil against Candida albicans.
Manohar V, Ingram C, Gray J, Talpur NA, Echard BW, Bagchi D, Preuss HG.
Mol Cell Biochem., 2001 Dec, 228(1-2), 111-117.
Oregano Oil Successfully Treats Upper Respiratory Tract Infections
The previous three studies should be enough to indicate what’s going on with oregano. In humans and in the laboratory, oregano kills a wide range of microorganisms. The third study listed above demonstrates that the antiseptic properties of oregano can be profound, meaning the difference between life and death for the mice in that study.
This next study gets right to the heart of the matter. The study investigated the effect of a nasal spray consisting of several essential oils including oregano oil in 60 humans with upper respiratory tract infections (the sore throat and congested lung infections that often accompany a cold). This study is of the highest calibre, as it is a randomized, double-blind, placebo-controlled trial. The patients were split into two groups, one group received the treatment while the other group received a placebo. Neither the patients nor the doctors and nurses who interacted with them knew which patients received the treatment, and which did not. (The best medical studies are done this way so that the observations and results will reflect only the results of treatment, and will not be affected by biases that the doctors or patients may have for, or against, the treatment.) The statistical analysis showed that 20 minutes following the treatment, the patients who had received the treatment reported a greater improvement in symptom severity compared to participants in the placebo group.
They describe their nasal spray as providing a “significant and immediate improvement in symptoms of upper respiratory ailment”.
4. Treatment of upper respiratory tract infections in primary care: a randomized study using aromatic herbs.
Ben-Arye E, Dudai N, Eini A, Torem M, Schiff E, Rakover Y.
Evid Based Complement Alternat Med., 2011, 690346.
Oregano Oil and the Immune System
This next study is interesting because it establishes a link between oregano oil and the boosting of the immune system. In this study oregano oil was fed to nursing pigs. (Again, this was a placebo-controlled study, so half of the pigs received oregano oil supplementation, and other half did not. The results were found by comparing the two groups.) The oregano oil increased the number of white blood cells in the pigs’ milk, which strongly suggests that it boosted the immune system of the pigs. What’s also interesting is that the piglets of the mothers who received oregano oil, drank more milk, demonstrating a positive effect for the children of nursing mothers who take oregano oil supplements. (The piglets weren’t directly given any oregano oil, they only received its benefit through their mothers’ milk.)
5. Effect of dietary supplementation of oregano essential oils to sows on colostrum and milk composition, growth pattern and immune status of suckling pigs.
Ariza-Nieto C, Bandrick M, Baidoo SK, Anil L, Molitor TW, Hathaway MR.
J Anim Sci., 2011 Apr, 89(4), 1079-1089.
Oregano Oil and Colesterol
Getting away from colds and sinus infections for a moment, I think the following paper is interesting. This paper presents a study of orally taken oregano in hyperlipidemic human patients. (Hyperlipidaemia just means that these people have elevated levels of fat in their blood, for example too much cholesterol.) After regularly taking oregano oil supplements following each meal for 3 months, these patients had improved lipid profiles including higher HDL (good cholesterol), lower LDL (bad cholesterol), improved antioxidant status (which, theoretically, could help fight cancer and reduce heart disease), and improved endothelial function (healthier veins and arteries) compared to those who did not take the oregano supplement.
6. Effects of Origanum onites on endothelial function and serum biochemical markers in hyperlipidaemic patients.
Ozdemir B, Ekbul A, Topal NB, Sarandöl E, Sağ S, Başer KH, Cordan J, Güllülü S, Tuncel E, Baran I, Aydinlar A.
J Int Med Res., 2008 Nov-Dec, 36(6), 1326-1334.
Oregano Oil and Cancer
This next paper is really about the cancer fighting qualities of rosemary extracts, but does make this interesting statement in the abstract: “One study in particular observed an inverse relationship between consumption of Mediterranean herbs such as rosemary, sage, parsley, and oregano with lung cancer.” The author of this paper is definitely more interested in rosemary, but it’s interesting to see oregano described as a potential cancer fighter.
7. Carnosol: a promising anti-cancer and anti-inflammatory agent.
Cancer Lett., 2011 Jun 1, 305(1), 1-7.
More: Oregano and Cancer
This paper tested an extract from Moroccan oregano (Origanum compactum Benth.) against a laboratory strain of human breast cancer cells and found the oregano extract to be effective at killing the cancer. A laboratory-bench experiment should not be viewed in the same light as a proper clinical trial with human patients, but nevertheless this provides a further indication that oregano may have cancer fighting properties.
8. Antiproliferative effect of extracts from Aristolochia baetica and Origanum compactum on human breast cancer cell line MCF-7.
Chaouki W, Leger DY, Eljastimi J, Beneytout JL, Hmamouchi M.
Pharm Biol., 2010 Mar, 48(3), 269-274.
Oregano Oil Review Paper: The Big List of Health Benefits
It is probably wise to view laboratory-bench research as a little less relevant, simply because it’s so removed from real human physiology (cells in a Petrie-dish just aren’t the same thing as cells in a human body). The “gold-standard” on the other hand, is high-quality placebo-controlled, double-blind studies using human patients. But there is an important third kind of research paper that is probably as important as the high-quality gold standard studies are, and these are the review papers. Review papers collect and interpret the results of many (usually gold-standard) studies, and thus can draw conclusions and provide perspectives that individual studies cannot.
The last paper we shall cover is a review paper that lists a wide range of beneficial health effects due to oregano, and in particular carvacrol.
The properties of oregano include:
- Antimicrobial and antiparasitic (kills microorganisms like bacteria, fungi, and yeasts, and parasites)
- Insecticidal (kills and repels insects)
- Antitumor (effective against cancer)
- Antimutagenic and antigenotoxic (help reduce damage to one’s DNS)
- Analgesic (naturally relieves pain)
- Antispasmodic (relieves spasms)
- Anti-inflammatory (reduces inflammation and discomfort associated with infection)
- Angiogenic (aid to the formation of new blood vessels)
- Antiplatelet (aids blood situation)
- AChe inhibitory (can help against Alzheimer’s disease, and Glaucoma)
- Antielastase (counteracts poison)
- Antihepatotoxic (detoxes the liver)
- Hepatoprotective (protects the liver)
- Aids in gastrointestinal ailments
9. Biological and pharmacological activities of carvacrol and carvacrol bearing essential oils.
Curr Pharm Des, 2008, 14(29), 3106-3119.
Study #4 showed that inhaled oregano oil helps with upper respiratory tract infections (a.k.a, the throat and congested lung infections that often accompany a cold). So, there definitely is strong evidence that oregano oil helps people with colds. Unfortunately, no one has undertaken a gold-standard study of the effects of orally-taken oregano oil specifically against the common cold and related (sinus, throat, lung) infections. But there is a lot of evidence here to suggest that eating oregano oil boosts your immune system, fights off microorganisms, and helps in a number of other ways.
The other thing to remember is that we’re talking about oregano here, the plant you probably have growing in your garden, that you have probably eaten a million times in salads and on the meat you BBQ (if not, try it, it’s good). There are no side-effects, complications, or counter-indications, unless you are allergic. Oregano is a regular food, so it is pretty safe to eat.
I leave you to make up your own mind regarding oregano. But I will tell you this: I’ve started taking oregano regularly, not just during cold season. Lower cholesterol, fewer gastro-intestinal infections, and the potential to improve my immune system and fight cancer have convinced me.