How does watercress support our gut health….
Rapidly growing research is demonstrating the microbiota to be protective against Allergy, Inflammatory disease such as Rheumatoid Arthritis and Inflammatory Bowel Disease (Bo et al 2018), Diabetes, Obesity and Weight Control, some Cancers and Mental illness to name a few. In addition, they’re vital in the correct development and functioning of our Immune System (Alexander et al 2017) and have a potential role in Sports Performance.
Dietary fibre and polyphenol anti-oxidants act as prebiotics - the energy source for our microbiota. Watercress is a brassica with extremely high levels of these antioxidants, known as Flavanoids, and of course, fibre. This review therefore discusses the potential role of Watercress as part of a balanced diet in optimising our gut microbiome and therefore our health.
The science so far…
‘Gut health’ is rapidly gaining popularity among the health-conscious - we don’t fully understand how our gut bacteria exert their many beneficial effects yet; research is only just beginning to provide the many answers we need. We do know that although our DNA is 99.4% the same as the next person, similarities in our microbiome are only 10 – 30%. And the Good News? We can alter our microbiome beneficially and rapidly, with diet. (Okeefe et al 2015) Prof Tim Spector at King’s College, London, is currently doing the PREDICT study, looking at the response of the microbiota to different diets, using twins; same DNA and lifestyle, therefore diet becomes the variable factor.
In ‘trying to close the stable door after the horse has bolted’, scientists are keen to highlight key research findings so far (Valdes, Spector et al 2018):
How do gut bacteria influence our health?
Metabolites: Fibre and polyphenols are not digested in the small intestine like most nutrients. Instead they pass to the large intestine where our microbiota extract energy from them by fermentation producing metabolites. Often, we can’t get these metabolites from any other source - flavonoid anti-oxidants can’t be activated without our microbiota. These metabolites are of many different types including Short Chain Fatty Acids (SCFAs) with vital roles - the anti-inflammatory role of Butyrate on our gut health being a good example along with Amino Acids, Neurotransmitters and Vitamins.
Epigenetics: This refers to the ability of gut bacteria and their metabolites, to alter the function of cells by changing cells’ gene expression rather than altering the DNA.
Gut bacteria and our Immune System
As 80% of our immune system is located in the wall of our intestine, the microbiota has an important role ‘exercising’ it and ensuring it develops correctly. (Power et al 2014) With the knowledge that maternal bacteria from childbirth are the first to colonise the gut of new-borns, it should be no surprise that babies born by caesarean section are shown to be at risk from a less well-developed immune system. So, we all begin life with an individual microbiome, some more beneficial than others, but which we can influence to our own benefit, with our food choices.
Our Mental health, Mood and Appetite
Scientists are currently studying the link between diet and mental disease via the effect of the microbiota on our immune system, anti-oxidants and other SCFAs. Commonly known as the gut-brain axis, the microbiome is known to exert its effect on mental health including our reaction to stress and depression, with studies on mice showing an increase in their stress behaviour when born into a sterile environment. Furthermore, we’re dependent upon our gut bacteria for our ‘happiness hormone’ Serotonin as these microbes are an essential source of its precursor Tryptophan, a protein building-block that we can’t make ourselves. (Clarke et al 2013) The SCFA metabolite Acetate, is also being studied for its neurotransmitter effects and is already known to signal a ‘feeling of fullness’ to the brain once absorbed into the blood stream.
Via epigenetics, the microbiota metabolite, butyrate, has been shown to inhibit cancer cells in several studies, by its action on chemicals called cytokines within the immune system. In particular, colon, prostate and breast cancer. (Pulliam et al 2016). Valder 2018 refers to the apoptosis, or ‘killing off’ of colon cancer cells by butyrate and the outcome of treatment with chemotherapy has also been shown to be influenced by the microbiome. (Alexander et al 2017)
As with much of the current research on the microbiome, the majority of the evidence of its effect on Obesity comes from studies on mice. However, we do know that long term weight gain in humans is associated with a poor microbiota diversity which is worsened with a low fibre diet. (Valdes et al 2018)
Protein metabolites produced by our gut bacteria help to maintain tight junctions between the epithelial cells which line our gut wall. This optimises its barrier function in protecting against the inappropriate absorption of compounds such as gluten, resulting in allergy.
Valder 2018 describe the role of butyrate having beneficial effects on intestinal glucose and energy balance.
Watercress – a brassica to optimise our microbiome?
This baby leaf brassica has a lot to shout about being an excellent source of many beneficial micro-nutrients. As far as our gut bacteria are concerned though, it’s the high content of polyphenol antioxidants – Flavanoids, in watercress which is of key interest as these are an important energy source for our microbiota (Selma et al 2009) (Ozdal et al 2016). Additionally, research has shown a high correlation between polyphenols and Vitamin C in brassicas and corresponding anti-oxidant activity (Martinez-Sánchez et al 2008). Watercress is a brassica with exceptional Vitamin C levels (43 mg Vit C/100g). As Flavanoids are also known to inhibit pathogenic bacteria (Yixie et al 2015), the potential in Watercress as an excellent food to optimise our microbiome is clear.
Watercress is already being studied for its ability to enhance patients’ response to chemotherapy due to its isothiocyanate content. In addition, there is clear potential for its additional flavonoid antioxidants in reducing cancer risk and in chemotherapy success, via their pre-biotic function.
In being an excellent source of prebiotics, watercress is likely to enhance energy balance as described above. This, in addition to its recognised highly bioavailable protein content for muscle repair and enhanced post-exercise rehydration, suggest its role in sports performance has much potential.
We know a diet rich in fibre and polyphenols not only promotes our gut bacteria, but also ensures we benefit from the roles of vital metabolites in optimising our health and metabolism. Watercress has both! Interestingly, optimal digestion of fibre requires food to be well chewed, otherwise the immune system at the gut wall may respond inappropriately to it and damage surrounding tissues as a result. The characteristic peppery flavour which occurs on chewing watercress, signifying activation of another antioxidant, isothiocyanate, is therefore potentially helpful in ensuring optimal digestion of its fibre by the microbiota.
The Path Ahead for Watercress and our microbiome…
Although we have evolved in a microbial world, it’s only recently that we’ve come to understand the benefits of these microbes in our health. Processed diets, an obsession with hygiene, caesarean births and a move to ‘live removed from the land’ have served to disadvantage our microbiome; new research is now helping us to understand how and why, we should nurture it.
Prof Tim Spector at his Royal Society of Medicine lecture 2018, described sourcing a wide range of fibre in our diet as the single most important food habit in optimising our gut microbiome, he refers to it as ‘tending our inner garden’. As watercress has v high levels of flavonoids along with Vitamin C, shown to enhance this effect, and with its fibre and year-round availability due to a v long season of growth (The Watercress Company provide it year-round to the UK market due to their overseas farms) it’s a remarkable leafy green to include in optimising our gut microbiome and therefore our long-term health and performance. Additionally, watercress has the potential to play a key role as part of a recovery diet after illness, pregnancy and antibiotic treatment, all of which are known to reduce our microbiome.