Researchers found that drinking a watercress-based beverage three times daily for two weeks helped people’s bodies get rid of harmful chemicals from pollution and smoke more effectively. In this study, 188 people either drank watercress juice or a placebo drink for two weeks, then switched after a break. Those who drank the watercress beverage showed significant increases in how much toxic material their bodies eliminated through urine—especially for dangerous chemicals like benzene and acrolein found in car exhaust and wildfire smoke. This suggests that adding watercress to your diet might be a simple way to help your body naturally defend itself against environmental toxins.

The Quick Take

  • What they studied: Whether drinking watercress juice helps your body remove toxic chemicals from pollution and smoke more effectively
  • Who participated: 188 adults (125 women, 152 non-smokers) from two different locations who completed the full study. Participants ranged in their exposure to environmental toxins
  • Key finding: People who drank watercress juice three times daily for two weeks removed 65.6% more of one harmful chemical (acrolein) and 37.3% more of another (benzene) through their urine compared to when they drank a placebo
  • What it means for you: Eating or drinking watercress may help your body naturally eliminate harmful toxins from air pollution and smoke. This could be especially helpful if you live in an area with poor air quality or near wildfires, though more research is needed to confirm long-term benefits

The Research Details

This was a randomized controlled trial, which is one of the strongest types of scientific studies. Researchers recruited 188 people and had them drink either a watercress-based beverage or a fake drink (placebo) three times daily for two weeks. After a four-week break to let their bodies return to normal, participants switched and drank whichever beverage they hadn’t tried before. This ‘crossover’ design means each person served as their own comparison, which helps researchers see the real effect of watercress.

The watercress drink was made from freeze-dried watercress powder containing a natural compound called PEITC (about 40 mg per day total). The placebo drink looked and tasted similar but contained only maltodextrin, a harmless starch. Researchers measured specific chemicals in participants’ urine that show how well the body is removing toxins—these are called mercapturic acids, which are the body’s way of packaging up harmful chemicals for removal.

The study was ‘single blind,’ meaning participants didn’t know which drink was the real watercress and which was placebo, but researchers did. This prevents people from unconsciously changing their behavior based on what they think they’re drinking.

This research design is important because it shows a direct cause-and-effect relationship between watercress consumption and the body’s ability to eliminate toxins. By having each person try both the watercress and placebo drinks, researchers could see clear differences in how the same person’s body responded to each. The crossover design also reduces the effect of individual differences between people, making the results more reliable.

This study has several strengths: it was randomized (participants were randomly assigned to drink order), it included a placebo control (so researchers could compare watercress to a fake drink), it had a reasonable sample size (188 people), and it measured objective biological markers (chemicals in urine) rather than relying on what people reported. However, 52 people who started the study didn’t complete it, which is fairly typical. The study was published in Carcinogenesis, a respected peer-reviewed journal focused on cancer research. One limitation is that the study only lasted two weeks of watercress consumption, so we don’t know if the benefits continue with longer use.

What the Results Show

When participants drank the watercress beverage, their bodies significantly increased the removal of six different harmful chemicals found in pollution and smoke. The most dramatic improvements were for acrolein (a chemical in car exhaust and wildfire smoke) which increased by 65.6%, and benzene (found in gasoline and pollution) which increased by 37.3%. These increases were statistically significant, meaning they were very unlikely to have happened by chance.

The other chemicals that showed increased removal were acrylonitrile, crotonaldehyde, methacrolein, and methyl vinyl ketone—all toxic substances people are exposed to through air pollution. Only one chemical tested (out of seven) didn’t show a significant increase. The watercress drink worked by activating the body’s natural detoxification system, which packages up these harmful chemicals so they can be safely removed through urine.

These results were consistent across different groups of participants, suggesting the effect is reliable. The dose used in the study (about 40 mg of the active compound per day) is achievable through eating watercress in your regular diet, making this a practical finding for everyday life.

The study found that the watercress effect was consistent regardless of whether participants were smokers or non-smokers, though the study primarily included non-smokers. This suggests the benefit might apply broadly to different populations. The researchers also noted that these findings are particularly relevant to people exposed to wildfire smoke, which contains many of the same toxic chemicals that watercress helps the body eliminate.

This research builds on earlier studies showing that watercress and related vegetables contain compounds that boost the body’s natural detoxification systems. Previous research had suggested these effects in laboratory settings, but this is one of the first human studies to measure actual changes in how much toxic material people eliminate from their bodies. The findings align with broader research showing that cruciferous vegetables (like watercress, broccoli, and cabbage) support the body’s defense systems.

The study only lasted two weeks of watercress consumption, so we don’t know if the benefits continue if you drink it longer or if they fade over time. The study measured only short-term changes in urine markers, not whether this actually reduces disease risk or improves health outcomes. While 188 people completed the study, 52 people who started didn’t finish, which could have affected results if those who dropped out were systematically different. The study was conducted at only two sites, so results might not apply equally to all populations. Additionally, the study didn’t measure whether watercress helps people who are heavily exposed to these toxins (like smokers or people in highly polluted areas) more than those with lower exposure.

The Bottom Line

Based on this research, eating or drinking watercress regularly may help your body eliminate harmful toxins from air pollution and smoke. The study used a freeze-dried watercress drink, but fresh watercress in salads or smoothies likely provides similar benefits since it contains the same active compounds. A reasonable approach would be to include watercress in your diet several times per week. However, watercress should be viewed as one part of a healthy lifestyle, not a replacement for avoiding pollution or other protective measures. Confidence level: Moderate—this is solid research, but we need longer-term studies to confirm lasting benefits.

This research is most relevant to people who live in areas with air pollution, near wildfires, or in cities with heavy traffic. People who smoke or are regularly exposed to secondhand smoke might benefit. However, this isn’t a substitute for quitting smoking or avoiding pollution. People with thyroid conditions should consult their doctor before significantly increasing watercress consumption, as large amounts may interfere with thyroid function. The study was conducted in adults, so we don’t have specific information about children.

The study showed changes in detoxification markers within two weeks of consuming watercress. However, this doesn’t mean you’ll feel different or notice health improvements that quickly. The actual health benefits from improved toxin removal would likely take months or years to become apparent. Think of it as a long-term investment in your body’s defense system rather than something that provides immediate noticeable effects.

Want to Apply This Research?

  • Track watercress consumption frequency (servings per week) and correlate with air quality index in your area. Users could log when they eat watercress and note any changes in respiratory symptoms or energy levels over 8-12 weeks, though individual results will vary
  • Set a goal to include watercress in meals 3-4 times per week. Users could add it to salads, smoothies, or sandwiches. The app could provide simple watercress recipes and send reminders on designated days to incorporate it into meals
  • Track watercress intake weekly and monitor subjective health markers like respiratory comfort, energy levels, and general wellness over 12 weeks. Users should also note air quality conditions in their area to see if watercress consumption correlates with feeling better on high-pollution days

This research shows that watercress may help your body eliminate certain toxic chemicals, but it is not a treatment or cure for any disease. Watercress should not replace medical treatment, avoiding pollution, or quitting smoking. If you have a thyroid condition, are pregnant, or take blood-thinning medications, consult your doctor before significantly increasing watercress consumption. Individual results may vary. This summary is for educational purposes and should not be considered medical advice. Always consult with a healthcare provider before making significant dietary changes, especially if you have existing health conditions.