How can watercress support cardio health & reduce blood pressure

Overview

Like beetroot, watercress contains natural nitrates. When chewed in the mouth these are converted by beneficial bacteria to nitrites and once in the stomach to gaseous nitrogen which enters the bloodstream dilating blood vessels and LOWERING blood pressure.

Detail

A recent report in The Guardian links age and lifestyle to blood pressure and our heart health:

Prof Bryan Williams, a specialist in hypertension at University College Hospital in London, said: “[The study] gives us a glimpse at what a normal blood pressure trajectory would be like without the impact of westernisation – many more people would have a normal blood pressure throughout life.”

The hypertension seen in older people in western countries such as the UK, he added, was caused by a stiffening of the large arteries. “This most likely represents some genetic predisposition but is powerfully influenced by lifestyle, as suggested by this study. It points once again to the importance of a healthy lifestyle to delay ageing of the arteries and delay the rise in blood pressure with age.”

The good news is that it’s never too late to improve our diets and watercress may be a great way to do this.

Does watercress lower blood pressure?

Like beetroot, watercress contains natural nitrates. When chewed these nitrates are converted to nitrites by specialist bacteria found naturally at the back of our mouth. Once the nitrites enter our stomach they convert into a gaseous form of nitrogen (NO) which enters our bloodstream. The effect on our cardiovascular system is to dilate blood vessels which decreases blood pressure; this is known as vasodilation. 

Figure 1. The path of dietary nitrate, derived from consuming leafy green vegetables. Systemically absorbed nitrate is concentrated 10-fold in the salivary glands (left panel) and undergoes an entero salivary circulation where it is reduced to nitrite by bacterial nitrate reductases on the dorsal surface of the tongue, and swallowed into the stomach providing a source of systemically available nitrite/NO. In the right panel we can see how nitrite is transported in the arterial circulation to resistance vessels, where lower O2 tension favours the reduction of nitrite to NO, causing vasodilation, with consequent lowering of blood pressure. (Reference 90)

Cardiovascular health

It has been estimated that eating at least 5 portions of a variety of fruit and vegetables a day could reduce the risk of deaths from chronic diseases such as heart disease and stroke by up to 20% (Department of Health (2000) The NHS Plan, London: Department of Health). Causal mechanisms are still being clarified, but may involve reduced lipoprotein oxidation and lipid homocysteine and blood pressure reductions. Proposed beneficial components of vegetables and fruit include: antioxidant nutrients including vitamin C, folate, flavonoids, lutein, glucosinolates, fibre and minerals such as potassium and vitamin B6 (References 67, 68).

The EPIC (European Prospective Investigation into Cancer and Nutrition) Norfolk population study found that plasma ascorbic acid (vitamin C) concentration was inversely related to all-cause mortality and particularly cardiovascular disease and ischaemic heart disease in both men and women (Reference 69). A rise in plasma ascorbic acid, equivalent to 50g of fruit or vegetable intake, was independently associated with about a 20% reduction in all-cause mortality.

While no studies have been carried out with watercress to specifically assess its potential to help maintain cardiovascular health, watercress is rich in vitamin C and a good source of most of the identified beneficial components. In addition, Gill et al (Reference 24) found that blood triglyceride levels were reduced by about 10% after the 8-week test period of watercress consumption