Scientists discovered that colistin, an antibiotic used in animal farming, can end up in lettuce we eat. Researchers developed a new test to detect this antibiotic and studied how it affects lettuce plants. They found that colistin can damage lettuce growth by interfering with how plants make energy and process nutrients. However, the good news is that lettuce samples from local supermarkets contained very low levels of colistin—so low that eating this lettuce poses minimal health risk to people. The study suggests we should keep monitoring antibiotic residues in vegetables, especially as antibiotic resistance becomes a bigger global problem.

The Quick Take

  • What they studied: Whether colistin (an antibiotic used in farm animals) that ends up in soil and water can accumulate in lettuce and cause harm to the plant and potentially to people who eat it.
  • Who participated: The study used lettuce plants grown in controlled laboratory conditions and real lettuce samples purchased from local supermarkets. No human participants were involved.
  • Key finding: Colistin can damage lettuce growth and plant cells at higher doses, but the amounts found in supermarket lettuce were so small that eating this lettuce appears safe for people based on current exposure levels.
  • What it means for you: You likely don’t need to worry about colistin in the lettuce you buy at the grocery store right now. However, this research highlights why monitoring antibiotic residues in food remains important as antibiotic resistance becomes a bigger health concern worldwide.

The Research Details

Researchers created a new laboratory test using advanced technology (LC-MS/MS) to detect and measure colistin in lettuce. This test is faster and more environmentally friendly than older methods. They first tested the method’s accuracy using lettuce samples spiked with known amounts of colistin at different levels (10, 30, 100, and 300 micrograms per kilogram). The test successfully detected colistin with good accuracy, recovering 73-91% of the antibiotic added.

Next, they grew lettuce plants in controlled conditions and exposed them to different doses of colistin to see how the antibiotic affected plant growth, energy production, and stress responses. They measured various plant chemicals and structures to understand the damage mechanism. Finally, they tested real lettuce samples from local supermarkets to see what colistin levels people actually encounter when eating vegetables.

This research matters because colistin is widely used in veterinary medicine (treating farm animals), and most of it gets excreted in animal waste that eventually reaches soil and water. Until now, nobody had systematically studied whether colistin accumulates in vegetables we eat or what damage it might cause. Developing a reliable detection method is crucial for monitoring food safety as antibiotic resistance becomes a major global health threat.

The study’s strength lies in its rigorous methodology: the detection method was validated with multiple quality checks, recovery rates were acceptable (73-91%), and the limit of detection was very low (5 micrograms per kilogram). The researchers used real supermarket samples to confirm their findings apply to actual food. However, the study focused only on lettuce and colistin—results may not apply to other vegetables or antibiotics. The study was conducted in a laboratory with controlled conditions, which may not perfectly reflect real-world exposure scenarios.

What the Results Show

Colistin significantly slowed lettuce growth in a dose-dependent manner, meaning higher doses caused more damage. The antibiotic damaged the plant’s mitochondria (the cell’s energy factories) and chloroplasts (the structures that capture sunlight for energy), reducing the plant’s ability to produce energy through photosynthesis.

Colistin triggered an imbalance in plant chemistry by disrupting a specific metabolic pathway involving fatty acids and hormone-like molecules. This disruption caused the plant to accumulate harmful molecules called reactive oxygen species, which are like cellular rust that damages plant tissues. The plant’s defense systems (antioxidant enzymes) tried to fight back but became overwhelmed.

When researchers tested real lettuce from supermarkets, they found colistin present in some samples, but at very low levels. Using standard health risk calculations, the amount of colistin people would consume from eating this lettuce was far below levels considered dangerous. The health risk score was below 1, which means the risk is considered low.

The study found that colistin may slightly help lettuce seeds germinate (sprout), but this effect was too small to be statistically significant. The research also identified specific chemical changes in the plant’s metabolism, including increased levels of certain inflammatory molecules (11-HETE) and decreased levels of protective molecules (5,6-DHET and prostaglandin G2). These chemical changes help explain how colistin damages plant cells at the molecular level.

This is the first study to systematically examine colistin accumulation in vegetables and its toxic effects on plants. Previous research has documented colistin resistance in bacteria and its use in veterinary medicine, but nobody had investigated whether colistin reaches food crops or what happens when plants are exposed to it. This research fills an important gap in understanding antibiotic contamination pathways from farms to food.

The study focused exclusively on lettuce—results may differ for other vegetables with different root systems or growing conditions. The laboratory experiments used higher colistin doses than typically found in nature to understand the damage mechanism, so real-world effects might be less severe. The study didn’t examine long-term accumulation of colistin in soil or how it might interact with other contaminants. Additionally, the research didn’t investigate whether cooking or washing lettuce reduces colistin levels. The sample size of supermarket lettuce tested wasn’t specified, so we don’t know how representative these findings are of all lettuce available.

The Bottom Line

Based on this research, there is no need to avoid eating lettuce due to colistin concerns—the current levels found in supermarket lettuce appear safe for consumption (confidence level: moderate). However, consumers can take simple precautions: wash lettuce thoroughly before eating, and support agricultural practices that reduce unnecessary antibiotic use in farming. Policymakers should continue monitoring antibiotic residues in food crops as part of broader food safety programs (confidence level: high).

Everyone who eats vegetables should be aware of this research, but it’s especially relevant for parents concerned about children’s food safety, people with compromised immune systems, and policymakers working on food safety regulations. This research is less immediately relevant to people with specific colistin allergies, as the amounts in lettuce are extremely small. Farmers and agricultural professionals should care about this research because it highlights how antibiotic use in livestock can reach food crops.

The health effects from eating colistin-contaminated lettuce would not be immediate—any potential harm would develop over months or years of consistent exposure to high levels. Since current lettuce levels are low, no timeline for health effects applies to typical grocery store lettuce consumption. However, if antibiotic residues in food increase significantly in the future, health effects could develop over extended periods of exposure.

Want to Apply This Research?

  • Track weekly vegetable intake and source (supermarket, farmers market, home-grown) to monitor dietary exposure to potential contaminants. Users can log lettuce consumption frequency and note any digestive symptoms to identify personal patterns.
  • Users can implement a simple vegetable washing routine: rinse lettuce under running water for 15-20 seconds before eating, and consider soaking in water for 2-3 minutes for extra cleaning. Log this habit in the app to build consistency and track whether washing practices correlate with any health changes.
  • Create a long-term food safety log that tracks vegetable sources, washing practices, and any gastrointestinal symptoms. Set monthly reminders to review patterns and adjust sourcing or preparation methods if needed. Users can also track antibiotic-related health news in their region to stay informed about food safety updates.

This research suggests that colistin levels currently found in supermarket lettuce pose low health risk based on standard food safety assessments. However, this study was conducted in laboratory conditions and may not reflect all real-world scenarios. Individual health risks may vary based on overall diet, age, and health status. If you have concerns about antibiotic residues in food or experience unusual symptoms after eating vegetables, consult a healthcare provider. This information is for educational purposes and should not replace professional medical or nutritional advice. Pregnant women, young children, elderly individuals, and immunocompromised persons should discuss food safety concerns with their healthcare provider.