Origanum vulgare (Oregano) is a spice. Its essential oil component, oil of oregano, is sold as an immune booster. The oil has various antimicrobial properties and can preserve food quality during storage. Human evidence for supplementation is lacking.
Primary Information, Benefits, Effects, and Important Facts
Origanum vulgare is the botanical name for the spice oregano. It is commonly used to flavor food or brew tea. The essential oil of oregano also has several alternate uses. It is made up primarily of carvacrol. The leaves of the plant contain a variety of antioxidant compounds, such as rosmarinic acid.
Traditionally, a leaf of Origanum vulgare is taken alongside a meal to aid digestion. One of the active components, thymol, is structurally similar to menthol, which is found in peppermint and is known to relax the soft tissue of the throat and stomach.
The oil of Oreganum vulgare is antibacterial, and has been used to prolong the shelf life of food products by reducing the rate of microbe growth and reducing the spoilage of fatty acids, which occurs when food products like meat go bad.
There is not much human evidence on supplementing either the leaf or oil form of Oreganum vulgare. The oil’s antioxidant aspect seems to be comparable to vitamin Cex vivo (outside the body). Origanum vulgare hinders bacterial replication, but further research is needed to pinpoint the exact mechanism.
The antibacterial properties of oregano oil suggest it is effective at warding off infection and boosting the human immune system, but human evidence for these effects is lacking. The lone study noting substantial efficacy against intestinal infection was funded by a manufacturer of oregano oil.
The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what effects origanum vulgare has on your body, and how strong these effects are.
Grade
Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
?
The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome
Magnitude of effect
?
The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
?
Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
One lone study (potential financial influence) has noted ablation of parasites in infected humans (77% of study group) and a reduction otherwise as assessed by stool samples.
Origanum vulgare (of the family labiatae[1]) is a spice and tea that is commonly referred to as oregano, with the essential oil derived from this plant referred to as oil of oregano. This plant is botanically related to another spice known as Marjoram (Origanum majorana) and is commonly called 'wild marjoram' due to this relationship.
It is traditionally used as a medicinal carminative and stomachic (taken with meals to reduce gastrointestinal distress, sometimes as a tea[2]) as well as for diuretic and emmenagogue purposes.[3] Other indications include analgesia and antiinflammation, such as for chronic rheumatism, toothache, and earache.[3]
1.2. Composition
The dried leaves of origanum vulgare (excluding the essential oil component) contain:
4'-O-beta-D-glucopyranosyl-3',4'-dihydroxybenzyl protocatechuate (Oreganol A[6] estimated at 3.8mg/g dry weight[8]) and the same glycoside for 4-O-methylprotocatechuate (Oreganol B[8])
Flavonoids eriocitrin (17.20 mg/g in the water extract[5]), apigenin (5.97 mg/g of the 7-O-glucoside in the water extract, aglycone less than 0.03mg/g[5]), luteolin (3.89mg/g of the 7-O-glucoside and 0.61mg/g of the aglycone in the water extract[5]), chrysoeriol, diosmetin, quercetin (0.70mg/g in the water extract[5]), and eriodictyol[3]
The composition of the dried leaves of oregano (excluding the essential oil component) includes a large amount of phenolics, which is fairly standard amongst plants, with the only unique components being phenolic structures known as oreganols (which are structured somewhat similar to rosmarinic acid). Triterpenoids such as ursolic acid may also be active in this plant.
The fresh essential oil component of origanum vulgare contains:
Carvacrol as the major component (characteristic odor of oregano) at 14.5%[9]
The essential oil of oregano is high in both carvacrol as well as thymol, despite the former being claimed to be the major component of oregano (since it carries the aroma of oregano). Some other components, such as β-fenchyl alcohol or γ-terpinene, may be in high enough levels to be active.
There is a pink flowered variant of oregano (origanum vulgare subspecies vulgare) which has a different essential oil composition which is high in β-Caryophylline (15.6-17.2%), Sabinene (2.5-9.1%), Spathulenol (5.3-6.1%), γ-Eudesmol (5.0-6.7%), p-cymeme (3.3-3.9%), α-humulene (2.1-2.8%), Germacrene D (4.5-9.8%), as well as β-ocimene structures such as (Z)-β-ocimene (0.8-4.0%), (E)-β-ocimene (0.9-3.9%), and allo-ocimene (1.1-4.0%) with various lesser components.[10] This variant does not appear to have a high carvacrol nor thymol content.
Other species of oregano may not have a high carvacrol content and have a widely different composition.
2Neurology
2.1. GABAergic Neurotransmission
The water extract of oregano appears to be able to induce analgesia when injected into the brain of rats, and both agonizing or antagonizing the GABAA receptors or inhibiting the GABAB receptors can block its effects while activating the GABAB receptors with baclofen augments it.[11]
The water extract of oregano contains components that may interact with GABAergic neurotransmission after injection into the rat brain, but the relevance of this information towards oral supplementation in humans is not known.
2.2. Analgesia
Intracerebral injections of a water extract from origanum vulgare appear to have analgesic properties in response to both a thermal and tail flick latency test[11] while intraperitoneal injections have shown efficacy in a formalin test.[12] These analgesic effects are thought to interact with GABAergic signalling since baclofen (GABAB agonist able to cause analgesia via these receptors[13]) augmented the analgesic properties while CGP35348 (GABAB antagonist) blocked the effects, and both GABAA agonism (muscimol) and antagonism (bicuculline) block the effects of oregano water extracts.[11]
Injections of oregano may reduce pain in rats, but this has yet to be seen with oral ingestion in humans, so its practical relevance to supplementation is not yet known.
3Cardiovascular Health
3.1. Atherosclerosis
A water extract of oregano (0.2-240mg/L) as well as the essential oil of oregano (2-4mg/L) appear to have in vitro antioxidative properties on LDL oxidation.[5]
Oregano can reduce LDL oxidation in vitro, but the effect on LDL oxidation following oral supplementation is not yet known.
4Inflammation and Immunology
4.1. Bacterial Interactions
The oil of oregano has traditionally been used as an anti-infective agent and antibacterial essential oil. The water extracts (teas) are used as carminative agents but do not appear to possess antibacterial properties, but do possess antioxidative properties.[9] The oil component has been used in conjunction with meat products or fruits (during storage) to reduce microbial growth[9][14] and to combat common microbes that grow in food products such as Salmonella enterica, Listeria monocytogenes, and Escherichia coli (MIC 3.12µg/mL).[10][15] The antioxidative properties of oregano are also desirable for the purpose of food preservation, as it can reduce oxidation of fatty acids in the food product with prolonged storage[16] and preserve the quality of oil products such as olive oil.[17][18]
The oil of oregano can be used in food production due to its antioxidant properties (preserving fatty acids from spoiling over time during storage) and its antimicrobial properties, since the oil seems to be able to suppress the growth and destroy the common food-borne microbes that cause illness.
Oil of oregano appears to have efficacy against a large range of bacteria, including Bacillus cereus and Bacillus subtilis (MIC 1.56µg/mL[10]), Staphylococcus aureus (MIC 3.12µg/mL or 0.6-1.25µL/mL[10][19]), and Eimeria tenella.[20] The antibacterial properties are thought to be tied to the bioactive carvacrol, which is active on its own.[21]
The antibacterial properties of oregano oil extend beyond bacteria found in the food supply. This is thought to be due to the carvacrol component, since it is active on its own.
5Interactions with Aesthetics
5.1. Skin
Origanoside has been noted to inhibit tyrosinase activity in cell culture at 10-20μg/mL by 16.9–28.6% (melanoma B16 cells) which was less than the references of arbutin or Vitamin C, suggesting possible comsmetic use in whitening skin.[22]. Additionally, origanol A has shown inhibitory properties on mushroom tyrosinase activity (IC50 of 2.47μg/mL) which is slightly less than the reference of kojic acid (1.75μg/mL), while origanol B was mostly inactive.[6]
When applied to the skin of mice, a topical gel containing origanoside over 10 days showed whitening properties associated with reducing the expression of pigment-forming genes (MITF, tyrosinase, and TRP-2).[22]
In vitro and animal studies suggest that phenolic compounds in oregano may have skin whitening properties when applied topically, although there is currently no evidence on human skin supporting this use.
6Peripheral Organ Systems
6.1. Intestines
In adults with chronic fatigue and gastrointestinal complaints, all those who tested positive for fecal parasites (14 out of a total of 33 people testing positive for blastocytis hominis, entamoeba hartmanni, or endomalix nana) who were then administered 600mg oil of oregano daily for six weeks had a reduction in parasite counts, and most (77%) experienced an elimination of parasites.[23] Alongside the reduction in parasites was a reduction in symptoms of fatigue and gastrointestinal complaints. Noteably, this study was funded by a producer of oregano oil, and no placebo control was used in this study.[23]
One study has shown a significant reduction in intestinal parasites in those infected, which resulted in a reduction of gastrointestinal and fatigue symptoms when the parasites were eliminated. This lone study has some issues (no placebo control and funded by an oregano oil manufacturer) and has not been replicated.
