Vitamin C deficiency is still surprising widespread in the UK adult population, without displaying the full-blown scurvy symptoms. The most common mild symptom is gum disease, or bleeding gums. Shoving a toothbrush round your mouth provokes the situation, and despite the TV advertising, toothpaste doesn't cure vitamin deficiency either.
Our ancestors did know something we've forgotten. The humble watercress was once-upon-a-time much prized as a dietary supplement. The Watercress Line in Hampshire is one vaguely remembered leftover. Most chalk rivers in southern England used to have lots of watercress beds, within living memory. The best watercress still comes from as high up the river flow as possible, to minimise contamination by animal effluent or parasites like flukeworm.
Modern science has identified more than 15 essential vitamins and minerals contained in this one herb – more iron than spinach, more calcium than milk, and more vitamin C than oranges.
Watercress is very low in calories, but contains phytonutrients like isothiocyanates and antioxidants with a plethora of disease-preventive properties. Gluconasturtiin, a glucosinolate compound providing the peppery flavor, is one of them, contained in the leaves and stems and providing phenethyl isothiocyanates, shown to inhibit carcinogens.
Vitamin K is by far the most prominent nutrient in watercress, with 312% of the daily recommended value. It forms and strengthens the bones and limits neuronal damage in the brain, which is helpful in treating Alzheimer's disease. There's also vitamin C, with 72% of the daily value, closely followed by vitamin A with 64%. Vitamin C provides top-notch infection-fighting power to stave off colds and flu, help maintain healthy connective tissue, and prevent iron deficiency. Vitamin A, also known as retinol, is essential for a properly functioning immune system and produces pigments in the retina of the eye, an absence of which can cause night blindness.
Manganese is a cofactor for the antioxidant enzyme superoxide dismutase, and calcium for strong bones and teeth come in high doses when you eat watercress. Antioxidant flavonoids like ß carotene, zeaxanthin, and lutein protect from lung and mouth cancers. B-complex vitamins include riboflavin, niacin, vitamin B6 (pyridoxine), thiamin, and pantothenic acid, all important for keeping your cellular metabolic functions at peak performance.