What Happens When You Cook This Food
Chlorophyll, the pigment that makes green vegetables green, is sensitive to acids. When you
heat greens, the chlorophyll in the leaves reacts chemically with acids in the greens or in
the cooking water, forming pheophytin, which is brown. Together, the pheophytin and the
yellow carotenes in dark green leaves give the cooked greens a bronze hue. Greens with few
carotenes will look olive-drab.
To keep the cooked greens from turning bronze or olive, you have to prevent the chlo-
rophyll from reacting with acids. One way to do this is to cook the greens in a large amount
of water (which will dilute the acids), but this increases the loss of vitamin C. A second
alternative is to leave the lid off the pot so that the volatile acids can float off into the air.
The best way probably is to steam the greens in very little water, or, as researchers at Cornell
University suggest, to microwave two cups of greens with about three tablespoons of water
in a microwave safe plastic bag left open at the top so that steam can escape. These methods
preserve vitamin C and cook the greens so fast that there is no time for the chlorophyll/acid
reaction to occur.
How Other Kinds of Processing Affect This Food
Freezing. Cooked frozen greens have more fiber and vitamin A than cooked fresh greens
because, ounce for ounce, they have less water and more leaf solids.
Medical Uses and/or Benefits
Lower risk of some birth defects. As many as two of every 1,000 babies born in the United
States each year may have cleft palate or a neural tube (spiral cord) defect due to their moth-
ers’ not having gotten adequate amounts of folate during pregnancy. The current RDA for
folate is 180 mcg for a woman and 200 mcg for a man, but the FDA now recommends 400 mcg
for a woman who is or may become pregnant. Taking folate supplements before becoming
pregnant and continuing through the first two months of pregnancy reduces the risk of cleft
palate; taking folate through the entire pregnancy reduces the risk of neural tube defects.
Vision protection. Dark greens are a rich source of the yellow-orange carotenoid pigments
lutein and zeaxanthin. Both carotenoids appear to play a role in protecting the eyes from
damaging ultraviolet light, thus reducing the risk of cataracts and age-related macular degen-
eration, which is a leading cause of vision loss in one-third of all Americans older than 75.
Possible lower risk of heart attack. In the spring of 1998, an analysis of data from the records
for more than 80,000 women enrolled in the long-running Nurses’ Health Study at Harvard
School of Public Health/Brigham and Women’s Hospital, in Boston, demonstrated that a diet
Greens