What is an EtG Test?
An Ethyl Glucuronide (EtG) test is a highly sensitive and widely-used method for detecting recent alcohol consumption. When the body ingests ethanol, the liver metabolizes a small portion into EtG, which is then excreted in the urine. Because EtG remains in the body long after alcohol has been eliminated—often detectable for up to 80 hours after consumption—it is a common biomarker for confirming abstinence in legal, rehabilitation, and workplace settings.
The test's high sensitivity, while beneficial for detecting even small amounts of alcohol, is also its primary weakness. Trace amounts of ethanol from sources other than alcoholic beverages can also produce a low-level positive EtG result. These are often referred to as false positives, and they are a significant concern for those required to maintain strict sobriety. Incidental exposure to products containing ethanol, such as mouthwash, hand sanitizers, and even certain foods, can lead to these confusing and potentially consequential test results.
Fermented foods that can produce EtG
Fermentation is a natural process where yeasts and bacteria convert sugars into alcohol. Many foods we consume regularly undergo some form of fermentation, which can leave trace amounts of ethanol behind. While the amounts are generally minuscule and harmless for most people, they can be a critical issue for someone facing an EtG test.
Kombucha
Kombucha is a popular fermented tea beverage known for its probiotic properties. The fermentation process, which uses a SCOBY (Symbiotic Culture Of Bacteria and Yeast), produces ethanol as a byproduct. While most commercial kombuchas are labeled non-alcoholic (often containing less than 0.5% alcohol by volume), some variations can contain higher levels, and homemade versions are particularly unpredictable. Consuming kombucha, especially in larger quantities, can lead to a positive EtG result.
Sauerkraut
Sauerkraut is fermented cabbage that relies on lactic acid bacteria. The process can also produce trace amounts of ethanol. Studies have shown that ingesting a significant quantity of sauerkraut can lead to detectable levels of EtG for several hours afterward.
Other fermented products
Other common fermented foods that may contain trace alcohol include:
- Soy sauce: Many soy sauces contain ethanol as a preservative, a byproduct of the fermentation of soybeans and wheat.
- Kefir: Both dairy and water kefir are fermented beverages that can contain small amounts of alcohol.
- Some yogurts: Some fruit-flavored yogurts, especially those with added sugar, can undergo minor fermentation, though the amount of ethanol produced is typically very low.
- Balsamic vinegar: This vinegar is made from fermented grape must and contains trace amounts of alcohol.
Naturally occurring ethanol in foods
Beyond fermented products, some foods naturally produce ethanol as they ripen or mature.
Overripe fruits
Fruits, particularly those with high sugar content, can begin to ferment as they ripen. This is especially true for fruits like bananas and certain juices if they are left at room temperature for an extended period. A study on bananas found that consuming a large quantity of very ripe fruit could result in detectable EtG in urine for several hours. Other fruits that can contain trace amounts include grapes, cherries, and pears.
Fruit juices
Certain fruit juices, including apple and grape juice, contain natural sugars that can ferment over time, especially if the juice is unpreserved or stored at room temperature. While fresh juice typically contains negligible amounts of ethanol, concentrations can increase as the juice ages, potentially leading to a positive EtG test after consuming large quantities.
Comparison: Foods vs. Alcoholic Beverages
To illustrate the difference in ethanol content, a comparison table can be helpful. This is not an exhaustive list but highlights the stark contrast between standard alcoholic beverages and the trace amounts found in food.
| Item | Approximate Alcohol Content (% ABV) | Potential for Positive EtG | Time to Clear (Urine) |
|---|---|---|---|
| Beer (12oz) | 5% | High | Up to 80 hours |
| Wine (5oz) | 12% | High | Up to 80 hours |
| Overripe Bananas | 0.2–0.4% | Low (with high consumption) | Up to 10 hours |
| Sauerkraut (per serving) | <0.2% | Low (with high consumption) | Up to 5 hours |
| Kombucha (12oz) | <0.5% | Low to moderate | Variable, depends on quantity |
| Soy Sauce | 1.5–2% | Very Low (trace amounts) | Minimal/Trace |
Preventing false positives from food
For individuals whose livelihoods or legal situations depend on maintaining strict alcohol abstinence, avoiding these foods is the most prudent course of action. This is particularly important with highly fermented or overripe products. Here are a few strategies to minimize risk:
- Choose non-fermented alternatives: Opt for non-fermented drinks and sauces whenever possible. Look for fresh ingredients and choose products with clear, unambiguous labels.
- Check food labels carefully: Always read the ingredients list for terms like "fermented" or preservatives derived from alcohol. Some foods with high sugar content and a low pH can produce alcohol over time, so check for freshness.
- Consider the quantity: The risk of a false positive is generally tied to the quantity of the offending food consumed. While a small amount of soy sauce might be harmless, consuming large portions of sauerkraut or overripe fruit could be problematic.
- Understand test cutoffs: Different testing programs use varying cut-off levels for EtG. While a low cut-off (e.g., 100 ng/mL) is highly sensitive, a higher one (e.g., 500 ng/mL) significantly reduces the likelihood of false positives from incidental exposure.
Conclusion
While a positive EtG test most often indicates alcohol consumption from beverages, it's a mistake to overlook the potential impact of everyday foods. Naturally occurring fermentation in items like kombucha, sauerkraut, and overripe fruits can introduce trace amounts of ethanol, which the body then metabolizes into EtG. For those subject to strict alcohol monitoring, understanding these dietary pitfalls is not just a matter of diligence but a necessity for ensuring accurate test results and protecting one's sobriety record. The key to mitigating this risk lies in informed dietary choices, careful label reading, and being aware of the highly sensitive nature of EtG testing. You can learn more about the science behind EtG testing on the National Institutes of Health website.
