On Food and Cooking

chlorophylls. Their main role there is to
protect chlorophyll and other parts of the
photosynthetic system. They absorb
potentially damaging wavelengths in the light
spectrum, and act as antioxidants by soaking
up the many high-energy chemical by-
products generated in photosynthesis. They
can do the same in the human body,
particularly in the eye (p. 256). Chloroplast
carotenoids are usually invisible, their
presence masked by green chlorophyll, but
it’s a good rule of thumb that the darker green
the vegetable, the more chloroplasts and
chlorophyll it contains, and the more
carotenoids as well.
About ten carotenoids have a nutritional as
well as aesthetic significance: they are
converted to vitamin A in the human
intestinal wall. Of these the most common and
active is beta-carotene. Strictly speaking, only
animals and animal-derived foods contain
vitamin A itself; fruits and vegetables contain