Dark leafy greens, including spinach, kale, Swiss chard, rocket, watercress, cavolo nero, and dark lettuce varieties, provide a nutritional density per calorie that no other food category can match. A 100-gram portion of raw spinach provides over 180 percent of the recommended daily vitamin K1, over 50 percent of vitamin A (as beta-carotene), over 15 percent of folate, meaningful amounts of magnesium and iron, and multiple antioxidant polyphenols, for approximately 23 calories.
The Key Nutrients in Dark Leafy Greens
- Vitamin K1: essential for blood clotting and bone mineralisation; dark leafy greens are the richest dietary source
- Folate: critical for DNA synthesis and repair; folate deficiency increases cancer risk and cardiovascular disease risk through homocysteine elevation
- Lutein and zeaxanthin: carotenoids that accumulate in the retina and brain; protective against age-related macular degeneration and associated with better cognitive function in older adults
- Nitrates: converted to nitric oxide in the body; improve endothelial function and exercise efficiency; beetroot and rocket are particularly rich
- Glucosinolates: compounds converted to anti-cancer isothiocyanates when the leaves are chopped or chewed; dark kale and watercress are particularly rich sources
- Magnesium: chlorophyll molecule contains magnesium at its centre; dark green colour is a reliable proxy for magnesium content
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