Benefits
Supports blood antioxidant status and carotenoid levels
In a crossover study, eating raw watercress daily for eight weeks roughly doubled plasma lutein and increased beta-carotene, which the study linked to a modulation of blood antioxidant status. A separate exercise trial found higher lipid-soluble antioxidants such as alpha-tocopherol after watercress. These are blood measurements in small groups, not clinical outcomes.
Lower oxidative damage to DNA in blood cells
In the eight-week crossover in sixty healthy adults, watercress was linked to less basal DNA damage in lymphocytes and about a quarter less oxidative purine DNA damage, measured with the comet assay. The changes were larger and clearer in smokers. This is a laboratory marker of DNA damage, not a measure of disease.
Less exercise-induced oxidative stress and lipid peroxidation
In a small controlled trial in ten healthy men, watercress taken once before exercise or daily for eight weeks blunted the rise in DNA damage, lipid peroxidation and hydrogen peroxide that followed exhausting exercise, alongside higher blood antioxidants. The trial was small and measured blood markers rather than performance.
Raises blood lutein and beta-carotene
Watercress is a concentrated dietary source of the carotenoids lutein and beta-carotene. In the eight-week crossover, daily watercress roughly doubled plasma lutein and raised beta-carotene by about a third compared with the control phase, reflecting the carotenoid content of the leaf.
Supports healthy blood pressure
In a four-week pilot in twenty-five middle-aged adults, a daily dried-watercress capsule dose lowered both systolic and diastolic blood pressure compared with placebo. The study was small and preliminary, and larger and longer trials are needed before watercress can be relied on for blood pressure.
Blood antioxidant capacity and oxidized-LDL markers
In the same blood-pressure pilot, watercress was followed by lower oxidized LDL and higher antioxidant capacity within the watercress group, and a lower estimated ten-year cardiovascular risk score. These within-group changes were not statistically significant when compared directly with the placebo group.
Mechanism of action
Gluconasturtiin releases PEITC when the leaf is crushed
Watercress stores the glucosinolate gluconasturtiin apart from the plant enzyme myrosinase. Chewing or crushing the raw leaf brings them together, and myrosinase converts gluconasturtiin into phenethyl isothiocyanate (PEITC). Cooking or long storage inactivates myrosinase and lowers how much PEITC is formed.
PEITC modulates detoxification enzymes in laboratory studies
In cell and animal studies, PEITC shifts the balance of phase I and phase II enzymes that process foreign compounds, lowering activation of some chemicals and speeding their excretion. In one study in smokers, watercress changed how a tobacco carcinogen was processed in urine. These are biochemical markers, not proof of disease prevention.
Supplies carotenoids and lipid-soluble antioxidants
Watercress is rich in the carotenoids lutein and beta-carotene and contributes tocopherols. Eating it raises these compounds in the blood, which may add to the body's antioxidant defenses; the human trials measured these blood levels and related oxidation markers rather than long-term health outcomes.
Clinical trials
Single-blind randomized crossover study of 85 g raw watercress daily for 8 weeks added to the habitual diet, measuring lymphocyte DNA damage, red-cell antioxidant enzymes, plasma antioxidants and lipids (Gill et al. 2007, Am J Clin Nutr).
60 healthy adults (30 men, 30 women; 30 smokers and 30 nonsmokers), mean age 33 years.
Basal DNA damage in lymphocytes fell about 17% and basal plus oxidative purine DNA damage about 23.9% during the watercress phase versus control, while the response to a hydrogen peroxide challenge was borderline. Plasma lutein rose about 100% and beta-carotene about 33%. Changes were greater in smokers. Biomarker outcomes, not disease endpoints.
Randomized controlled crossover study of watercress taken 2 hours before exercise (acute) and daily for 8 weeks (chronic), each with a no-ingestion control, measuring DNA damage and lipid peroxidation after an exhaustive exercise test (Fogarty et al. 2013, Br J Nutr).
10 apparently healthy men, mean age 23 years.
Exhaustive exercise raised DNA damage and lipid peroxidation during the control phases, while both acute and chronic watercress lowered these markers and reduced hydrogen peroxide accumulation after exercise. Lipid-soluble antioxidants rose with watercress. Very small; it measured blood markers, not performance.
Randomized placebo-controlled pilot study of 16 dried watercress capsules daily for 4 weeks, measuring blood pressure, arterial stiffness, lipids, oxidative stress markers and estimated 10-year cardiovascular risk (Kijkuokool et al. 2026, Antioxidants (Basel)).
25 Thai middle-aged adults with low-to-moderate cardiovascular risk (12 watercress, 13 placebo).
Systolic and diastolic blood pressure fell significantly with watercress versus placebo. Oxidized LDL, antioxidant capacity and the estimated 10-year risk score improved within the watercress group but did not reach significance compared with placebo. A small pilot; larger and longer trials are needed.
Controlled dietary study in which smokers avoided cruciferous vegetables, then ate about 57 g watercress at each meal for 3 days, with 24-hour urine collected to measure metabolites of a tobacco-specific carcinogen and of PEITC (Hecht et al. 1995, Cancer Epidemiol Biomarkers Prev).
11 smokers who kept their smoking habits constant.
During watercress eating, urinary output of the detoxified carcinogen metabolites (NNAL plus NNAL-glucuronide) rose about 33.5% and returned toward baseline afterward; estimated PEITC intake was 19 to 38 mg a day. A short biomarker study of how a carcinogen is processed, not a cancer-prevention trial.