Phytonutrients (phytochemicals)
Bioactive compounds made by plants (beyond vitamins and minerals) that serve as their defence and bring humans a variety of health benefits.
Phytonutrients (or phytochemicals) are thousands of compounds that plants make to protect themselves (against UV, pests and predators) and to give themselves colour. They are neither vitamins nor minerals, but they offer many benefits: polyphenols, carotenoids, glucosinolates, sulphur compounds, phytosterols and more.
The original angle (colours = families of molecules): a practical and memorable principle: the colour of a plant food reveals its dominant phytonutrients. Eating “the rainbow” ensures a diversity of protective compounds:
- Red (tomato, watermelon): lycopene, for the heart and prostate
- Orange/yellow (carrot, squash): beta-carotene, for vision and immunity
- Green (cruciferous vegetables, spinach): glucosinolates, lutein, chlorophyll, for detoxification and the eyes
- Purple/blue (blueberry, red cabbage, aubergine): anthocyanins, for the brain and blood vessels
- White (garlic, onion): sulphur compounds (allicin), for the cardiovascular system and immunity
The shared defence principle (xenohormesis): a fascinating angle: many phytonutrients are in fact stress/defence molecules of the plant (mild “toxins” against its aggressors). When we eat them, they trigger a hormetic response in us: they activate our own defences (the Nrf2 pathway, antioxidant enzymes). This is the xenohormesis theory: we “borrow” the plants’ stress signals to strengthen our own resilience.
This explains why “bitter” and intensely coloured plants (often the richest in defence compounds) are particularly beneficial: their bitterness signals these bioactive compounds. Modern breeding, which has made fruit and vegetables sweeter and less bitter, has paradoxically reduced their phytonutrient content.
The glucosinolates of cruciferous vegetables: a star example: broccoli, cabbage and rocket contain glucosinolates that are converted (by chewing or chopping) into isothiocyanates, including the famous sulforaphane, a powerful activator of antioxidant defences that has been studied in cancer prevention.
In practice: eat colourful and varied foods, include cruciferous vegetables, spices and “bitter” plants, and favour diversity rather than focusing on a single “superfood”.