Carotenoids
Plant pigments (yellow, orange, red) with antioxidant properties, some of which (beta-carotene) are precursors of vitamin A, while others (lutein, lycopene) have specific protective roles.
Carotenoids are the pigments that colour carrots, tomatoes, peppers and sweetcorn, and also (masked by chlorophyll) green vegetables. More than 600 have been identified, around fifty of them in the diet. They are classed in two groups:
- Provitamin A (beta-carotene, alpha-carotene): convertible into vitamin A
- Non-provitamin (lutein, zeaxanthin, lycopene): no conversion, but roles of their own
The original angle (cooking and fat unlock their power): a recurring counter-intuitive point: carotenoids are better absorbed cooked and with fat. The tough plant cell walls trap the pigments; cooking breaks them down and fat dissolves them.
Spectacular examples:
- Lycopene (tomato): tomato sauce cooked with olive oil releases far more lycopene than a raw tomato. Cooking multiplies its bioavailability
- Beta-carotene (carrot): cooked carrot + fat >> plain raw carrot
Eating raw “to preserve nutrients” is therefore sometimes counter-productive for carotenoids.
Valuable specific roles:
- Lutein and zeaxanthin: accumulate in the retina (macula), filter harmful blue light, and protect against AMD (macular degeneration). Sources: green vegetables, egg yolk, sweetcorn
- Lycopene: an antioxidant associated with cardiovascular and prostate protection. Sources: cooked tomato, watermelon, pink grapefruit
- Beta-carotene: provitamin A + antioxidant
A note on supplements: as with antioxidants, carotenoids as an isolated high-dose supplement can be harmful (beta-carotene in pill form increased the risk of lung cancer in smokers, in the ATBC/CARET trials). In whole foods, there is no risk. Another case where food beats the pill.