Our watercress health claims journey

HEALTH CLAIMS

Raw watercress is rich in vitamins A (as beta carotene), vitamin C and vitamin K1, and is a source of folate, vitamin B6, calcium and iron. These nutrients contribute to normal physiological functions when included as part of a varied and balanced diet. Because 100g of raw watercress contains over 15% (source) or 30% (rich in) of the nutrient reference values for these vitamins and minerals, the beneficial health effects for each nutrient in watercress can be applied(1):

Antioxidant activity – ‘where vitamin C contributes to the protection of cells from oxidative stress’. Oxidative stress occurs when there are too many free radicals in the body and not enough antioxidants to balance them. Free radicals are produced by the body during natural metabolism and especially after exercise (2).

Collagen/skin – ‘Vitamin C and A support the normal maintenance of our skin’, with vitamin C specifically involved in collagen formation, contributing to the skins structure and ability to repair.

Cognitive development - ‘Iron supports normal cognitive function in adults and in children it contributes to their normal cognitive development’. ‘Vitamin C has the added benefit of increasing iron absorption’! 

Immune support – ‘Vitamin A, C, Iron, vitamin B6 and folate all have a role in supporting the normal functioning of our immune system’, which acts to protect against harmful pathogens such as bacteria and viruses and also helps the body recognize and eliminate damaged or abnormal cells. ‘Vitamin C also supports our immune system during and after intense physical exercise’.

Reduced tiredness and fatigue – ‘Vitamin C, folate and vitamin B6 can help to reduce our levels of tiredness and fatigue’ and ‘iron has a role in normal energy yielding metabolism’.

Increased iron and its absorption and metabolism – ‘Vitamin C supports the absorption of iron’ from the watercress we eat and ‘vitamin A helps with the normal iron metabolism in our bodies’.

Musculosketal health – ‘Vitamin C contributes to normal collagen formation in bone’, by laying down a collagen scaffold in the bone. ‘Vitamin K also contributes to the maintenance of our bones’, by helping calcium bind to this scaffold. In addition ‘vitamin C supports collagen formation in cartilage and calcium contributes to normal muscle function’.

Psychological function – ‘Vitamin C, folate and vitamin B6 all have a role in helping with normal psychological function’, which relates to how our minds process daily activities.

Vision – Beta carotene is converted to vitamin A in the body, ‘which supports normal vision’, allowing us to see at low light levels.

Red blood cells, clotting and blood vessel formation – ‘Vitamin C helps maintain normal collagen formation for the normal function of blood vessels’. It also increases iron absorption supporting the normal formation of red blood cells and haemoglobin, which are needed for oxygen transport in the body. ‘Vitamin K₁ contributes to normal blood clotting’, helping the body respond appropriately to injury. Together, these nutrients support healthy blood, effective oxygen transport and strong blood vessels.

Pregnancy health – ‘Folate has a role in the process of cell division and supports maternal tissue growth during pregnancy’.

Consuming watercress as part of a balanced diet is a great start to optimising your nutrition – try filling your plate with a range of colours and nut/grain varieties to obtain as many phytonutrients and nutrients as possible.

Watercress in research studies

In addition to its vitamins and minerals, research has shown that watercress and watercress juice extract contains a variety of phytochemicals. Those most clearly identified include glucosinolate derivatives such as phenylethyl isothiocyanate (PEITC) and methylsulphinylakyl isothiocyanates (MEITCs), flavonoids such as quercetin and hydroxycinnamic acids and carotenoids such as beta-carotene, zeaxanthin and lutein.

Over the years there has been lots of research studies undertaken on watercress and watercress extracts assessing its anti-inflammatory potential, its antioxidant potential (in particular to protect DNA from damage) and the ability of PEITC to target cancer cells triggering programmed cell death. Watercress extract also contains a compound called dimethyl thiosulphate (or DMTS) which inhibits the enzyme urease, giving the extract wide potential applications in continence care, cosmetics, food and drink.

Cancer related research
Several scientific studies have explored the potential role of watercress in cancer prevention and support:

• A study in the US (1995) found that PEITC in watercress can help neutralise cancer-causing chemicals in the blood of smokers (3).

• Research from the University of Ulster (2007) examined markers of DNA damage in participants consuming watercress daily (4).

• In 2010, the University of Southampton found that PEITC could help block breast cancer cell growth by disrupting their blood supply in vitro and in vivo (5).

• In 2023, a randomised controlled trial in Thailand explored PEITC in a jelly formulation for patients with advanced oral and oropharyngeal cancer, focusing on markers of health and quality of life in a research context (6).

• Laboratory studies in 2024 examined PEITC and its effects on human malignant melanoma cells (7).

While these studies contribute valuable scientific understanding, more high-quality research is needed to explore potential applications, dosages, and relevance for the general population. None of these studies should be interpreted as evidence that consuming watercress has any cancer disease-prevention or cancer treatment effects.

Turning research into health claims we can put on our product!

While many studies suggest potential benefits of PEITC and other phytonutrients in watercress, these are not substantiated health claims. In the UK getting health claims approved requires submitting scientific evidence to the Nutrition and Health Claims Committee, whose experts review the data to ensure any claim is accurate, measurable and safe before it can appear on packaging or marketing materials.

Many claims aren’t approved because the evidence doesn’t meet regulatory standards. To succeed, studies must involve humans and demonstrate that the whole food—not just an isolated compound—provides the benefit. Without this kind of solid, directly relevant data, regulators won’t permit a health claim.

Future research

As growers of watercress, our capacity to conduct independent research is limited. However, we are very keen to collaborate with universities and research institutions to include watercress in scientific studies and help build a stronger body of evidence to support its health benefits.

We welcome interest from researchers worldwide who would like to explore the potential of watercress in their work. If you are interested in collaborating, please contact sarah.delvin@thewatercresscompany.com.

References

1. A BNF report for AHDB: A brief guide to nutrition and health claims in relation to watercress. British Nutrition Society. May 2018.

2. Kawamura T, Muraoka I. Exercise-Induced Oxidative Stress and the Effects of Antioxidant Intake from a Physiological Viewpoint. Antioxidants (Basel). 2018 Sep 5;7(9):119.

3. Hecht, S et al. Effects of Watercress Consumption on Metabolism of a Tobacco-specific Lung Carcinogen in Smokers. Cancer Epidemiol Biomarkers Prev 1995; 4 (1):877-884.

4. Gill, Chris IR et al. Watercress supplementation in diet reduces lymphocyte DNA damage and alters blood antioxidant status in healthy adults. Am J Clin Nutr 2007;85 (2):504 – 510.

5. Syed Alwi SS et al. In vivo modulation of 4E binding protein 1 (4E-BP1) phosphorylation by watercress: a pilot study. Br J Nutr 2010;104(9):1288-96.

6. Lam-Ubol A, Sukhaboon J, Rasio W, Tupwongse P, Tangshewinsirikul T, Trachootham D. Nutri-PEITC Jelly Significantly Improves Progression-Free Survival and Quality of Life in Patients with Advanced Oral and Oropharyngeal Cancer: A Blinded Randomized Placebo-Controlled Trial. Int J Mol Sci. 2023 Apr 25;24(9):7824.

7. Tragkola V et al. Naturally-derived phenethyl isothiocyanate modulates apoptotic induction through regulation of the intrinsic cascade and resulting apoptosome formation in human malignant melanoma cells. Toxicol Mech Methods. 2024;34(9):985-999.