What is Thujone and Why Is It Controversial?
Thujone is a ketone monoterpenoid found in several plant species, including wormwood (Artemisia absinthium) and common sage (Salvia officinalis). This compound became famous due to its association with absinthe, the potent alcoholic spirit made from wormwood. Thujone acts on the central nervous system, and in high concentrations, it can be toxic and may cause convulsions. This is why many countries regulate the amount of thujone in food and beverages, leading to the development of "thujone-free" versions of absinthe.
The controversy stems from the psychoactive and neurotoxic effects observed with high doses of thujone, which have historically been misattributed to the low doses found in traditional absinthe. While pure wormwood oil contains significant levels of thujone, and can be dangerous, the concentration in distilled absinthe is typically very low and unlikely to cause harm.
The Real Primary Compound in Thyme: Thymol
Thyme's aromatic properties and medicinal benefits are primarily due to its high concentration of thymol, a potent phenolic compound. Thymol is an isomer of carvacrol and is well-regarded for its strong antimicrobial and antioxidant activities, which account for many of thyme's traditional uses. The specific chemical profile of thyme, known as its chemotype, can vary significantly based on factors like climate, geography, and cultivation practices. For example, some chemotypes are high in thymol, others in linalool, and some in geraniol.
List of Common Thyme Chemotypes and Their Main Constituents:
- Thymol Chemotype: Dominated by thymol, with significant levels of p-cymene and gamma-terpinene.
- Linalool Chemotype: High concentration of linalool, known for its milder, less phenolic aroma.
- Geraniol Chemotype: Rich in geraniol and geranyl acetate, offering a sweeter, more floral scent.
- Thujanol Chemotype: Characterized by a high content of thujanol-4, this variety is known for being gentler on the skin.
Analysis of Thyme's Thujone Content
Studies on thyme's essential oil composition confirm that thujone is not a major component, and in many cases, it is either absent or present in negligible, trace amounts. Most analytical reports focus on the presence of thymol, carvacrol, and other key components, which are found in much higher concentrations. A 2011 report from the European Medicines Agency showed that while some herbs contain significant levels of thujone, the amount detected in thyme essential oil was extremely low or "not determined". This is in stark contrast to other plants like common sage, where thujone can make up a substantial portion of the oil's composition. The idea that thyme contains significant thujone is largely a misconception or based on isolated, low-level reports that are not representative of typical culinary and medicinal thyme.
Comparing Thyme, Wormwood, and Sage
The following table compares the typical chemical profiles of thyme, wormwood, and sage to highlight the differences in their thujone content.
| Feature | Thyme (Thymus vulgaris) | Wormwood (Artemisia absinthium) | Common Sage (Salvia officinalis) |
|---|---|---|---|
| Primary Active Compound | Thymol (phenolic compound) | Absinthin (bitter lactone) and Thujone | Thujone |
| Dominant Chemical Profile | Varies by chemotype, rich in thymol, p-cymene, γ-terpinene | High bitter compounds and alkaloids | High concentrations of α- and β-thujone |
| Thujone Content | Trace amounts, if any; not a significant component | Significant levels, especially in concentrated oils | Can contain over 20% thujone in its essential oil |
| Safety in Moderation | Generally recognized as safe (GRAS) for culinary use | Can be toxic in concentrated forms; regulated in foods/drinks | Safe for culinary use in small amounts, but high doses toxic |
Clarifying the Misinformation
The confusion about thyme's thujone content likely stems from several sources:
- Misclassification or Overgeneralization: Some sources broadly list a group of herbs that may contain thujone without specifying the typically low concentrations in thyme relative to other species like wormwood or sage.
- Isolated Chemotypes: While possible, a thyme chemotype with high thujone would be extremely rare and not representative of the widely used culinary and medicinal varieties.
- Name Similarity: The similarity between the words thyme, thymol, and thujone could lead to simple verbal confusion for some individuals.
Conclusion
In conclusion, thyme does not have thujone in any amount that is a cause for concern for typical culinary or medicinal uses. The primary and dominant volatile compound in thyme is thymol, a safe and well-studied phenolic compound known for its therapeutic properties. The trace amounts of thujone that might theoretically appear in some rare chemotypes of thyme are insignificant compared to the high concentrations found in other plants like wormwood and sage, which require stricter regulatory oversight. Consumers and herbalists can be confident that using standard varieties of thyme is safe, and its effects are due to its well-documented constituents, not the controversial thujone.
For more detailed information on essential oil safety, visit the National Association for Holistic Aromatherapy website.
