Watercress benefits: the 2026 trial used 8 g of dried capsules, not the vegetable

Key benefits

1. 01Early research

   LDL fell — in 26 people, single-blind, from capsules, in an exploratory study

   2026, Nutrients.

   Participants	26 people aged 40 to 59 at low-to-moderate cardiovascular risk
   Design	Randomised, single-blind, placebo-controlled, pilot
   Intervention	8 g a day of dried watercress capsules (about 195 mg glucosinolates)
   Duration	28 days
   Analysis	untargeted NMR metabolomics

   The results:

   Item	Result
   Metabolites identified	209
   Group discrimination (PLS-DA)	modest (Q2 = 0.268)
   Discriminant metabolites	27 (VIP > 1.5)
   Pathways significantly perturbed	18 — galactose and fructose/mannose metabolism (p<0.001) among them
   Metabolites that fell	linked to oxidative DNA damage, kynurenine metabolism, microbial co-metabolism
   Metabolites that rose	glycine, dimethylglycine
   LDL cholesterol	significantly reduced
   Other lipids	no consistent effect

   Start with what is good. It was placebo-controlled, and profiling metabolites without a target means the result is not fitted to a pre-chosen hypothesis. And LDL genuinely fell.

   But the weight this can bear is small, for four reasons.

   First, 26 people. Split in two, that is thirteen or fourteen an arm. The paper calls itself a pilot.

   Second, single-blind. Only the participants were masked; the researchers knew. That is not double-blind.

   Third, the separation between groups is weak. A Q2 of 0.268 is hard to call strong discrimination in metabolomics. The paper itself writes "modest discrimination".

   Fourth, capsules, not a vegetable. Eight grams of dried watercress powder. In fresh watercress that is well over 100 g, because watercress is mostly water. The 30 g that goes on a salad plate does not come close.

   The other trials used extracts too.

   2021, Phytotherapy Research gave a standardised watercress extract to overweight people with a physical disability and measured lipids and oxidative stress markers. A similar trial from the same group appeared in 2020. Both used extracts, in specific populations.

   This is the same structure as this site's celery entry. A result from an extract or a capsule does not carry across to eating the vegetable.

   The honest conclusion:

   • Eight grams a day of dried watercress capsules for 28 days lowered LDL and shifted metabolic pathways — that is the supported range
   • There was no consistent effect on other lipids
   • Twenty-six people, single-blind, a pilot, and the paper calls it exploratory
   • It is not evidence that a plate of salad does the same
   • The grade is "early research"

   [1][2]
2. 02Nutrition data

   11 kcal per 100 g — but 250 µg of vitamin K

   Per 100 g of raw watercress:

   • Vitamin K 250 µg — 208% of the daily value
   • Vitamin A 160 µg RAE, beta-carotene 1,910 µg
   • Lutein and zeaxanthin 5,770 µg
   • Vitamin C 43 mg
   • Calcium 120 mg, potassium 330 mg, phosphorus 60 mg, magnesium 21 mg
   • 11 kcal, protein 2.3 g, carbohydrate 1.29 g, fibre 0.5 g
   • Sodium 41 mg, manganese 0.244 mg, vitamin E 1.0 mg

   The 11 kcal catches the eye first. Lettuce is 15 and spinach 23. It is low even among leafy greens.

   But the most important number in this table is 250 µg of vitamin K.

   That is 208% of the daily value. Even the 30 g on a salad plate is 75 µg, 62% of the daily value.

   If you take warfarin, this number matters to you. Vitamin K is part of blood clotting, and warfarin works by interfering with it. A sudden rise in vitamin K intake reduces the drug's effect.

   This is the same issue set out in this site's kale and spinach entries, and watercress is high even among those.

   • If you take warfarin, talk to your clinician before starting watercress
   • This is not a reason to stop. What matters is keeping the amount steady
   • Suddenly eating a lot, or suddenly stopping, is the problem

   Lutein and zeaxanthin at 5,770 µg is a high figure too. As set out in this site's goji berry entry, these pigments accumulate in the macula. But this site found no trial that fed watercress and measured the eye. Kale and spinach carry more material.

   Calcium at 120 mg is high for a leafy green. It is 9% of the daily value, and calcium from plants does not absorb like the calcium in milk.

   Vitamin C at 43 mg is decent but heat-sensitive. As set out below, eating watercress raw is the natural approach.

   Handling.

   • Wash it well under running water. Watercress grows in water, and foraged watercress carries a risk of parasites such as liver fluke. Do not eat wild watercress raw
   • Buy cultivated. Commercial watercress is grown in controlled conditions
   • Trim the tough lower stems
   • Wrap it in damp kitchen paper in the fridge and it keeps for days. Standing it in water turns it soft quickly

   Taste. It has a distinctive peppery heat from compounds of the same family as in radish and mustard, a shared trait of cruciferous vegetables. That heat is what it contributes to a salad.

3. 03Not established

   Claims about cancer, detox and weight loss are unverified

   Several claims attach to watercress. The only one confirmed in people is the LDL finding above, and that was a pilot using capsules.

   "It fights cancer."

   Watercress is cruciferous, and there is a great deal of research on isothiocyanates — formed from glucosinolates — acting on cancer cells in the laboratory. They are the same family as broccoli's sulforaphane.

   An action observed in cells and animals is a different claim from an outcome in a person who ate the food. This site found no trial that fed watercress, measured cancer incidence or recurrence and compared against a control.

   There are small older studies in which eating watercress shifted markers of DNA damage. A DNA damage marker is an intermediate, and it does not show the outcome that follows. The 2026 trial above also reported a fall in metabolites linked to oxidative DNA damage — but those are metabolites, not cancer.

   "It detoxifies."

   There is research on cruciferous vegetables affecting liver detoxification enzymes. But "detox" is not a medically defined term. A claim about removing something from the body only means anything if it says what, how much, and measured how. This site found no such data.

   "It helps with weight loss."

   It is true that 100 g is 11 kcal. Filling a plate with low-energy vegetables gives the same fullness for fewer calories. That arithmetic follows straight from the composition.

   But this site found no trial that fed watercress, measured weight and compared against a control. And 100 g of a leafy green is more volume than it sounds — a plate actually carries about 30 g, which is 3.3 kcal.

   To summarise:

   • Confirmed by composition: vitamin K 250 µg, lutein and zeaxanthin 5,770 µg, vitamin A 160 µg, vitamin C 43 mg, calcium 120 mg, 11 kcal
   • Early: 8 g a day of dried capsules for 28 days lowered LDL (26 people, single-blind, pilot)
   • Not confirmed: cancer, detox, weight loss
   • What you must know: vitamin K is 208% of the daily value and interacts with warfarin

How to eat it well

What to watch out for