The New Complete Book of Food
having gotten adequate amounts of folate during pregnancy. The current RDA for folate is
180 mcg for a healthy woman and 200 mcg for a healthy man, but the FDA now recommends
400 mcg for a woman who is or may become pregnant. Taking a folate supplement 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. One cup shredded romaine lettuce has 78 mg folate.
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
providing more than 400 mcg folate and 3 mg vitamin B 6 daily, either from food or supple-
ments, might reduce a woman’s risk of heart attack by almost 50 percent. Although men
were not included in the study, the results were assumed to apply to them as well.
However, data from a meta-analysis published in the Journal of the American Medical
Association in December 2006 called this theory into question. Researchers at Tulane Univer-
sity examined the results of 12 controlled studies in which 16,958 patients with preexisting
cardiovascular disease were given either folic acid supplements or placebos (“look-alike” pills
with no folic acid) for at least six months. The scientists, who found no reduction in the risk
of further heart disease or overall death rates among those taking folic acid, concluded that
further studies will be required to ascertain whether taking folic acid supplements reduces
the risk of cardiovascular disease.
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.Adverse Effects Associated with This Food
Food-borne illness. According to the Centers for Disease Control and Prevention, from
1996–2005 the proportion of incidents of food-borne disease linked to leafy greens increased
by 60 percent. The highest proportion of these illnesses were due to contamination by noro-
virus (the organism often blamed for outbreaks of gastric illness on cruise ships), followed
by salmonella and E. coli. The illnesses were commonly associated with eating raw greens;
cooking the greens to a high heat inactivates the disease-causing organisms.
Nitrate poisoning. Lettuce, like beets, celery, eggplant, radishes, spinach, and collard and
turnip greens, contains nitrates that convert naturally into nitrites in your stomach, and then
react with the amino acids in proteins to form nitrosamines. Although some nitrosamines
are known or suspected carcinogens, this natural chemical conversion presents no known
problems for a healthy adult. However, when these nitrate-rich vegetables are cooked and left
to stand at room temperature, bacterial enzyme action (and perhaps some enzymes in the
plants) convert the nitrates to nitrites at a much faster rate than normal. These higher-nitrite
foods may be hazardous for infants; several cases of “spinach poisoning” have been reported
among children who ate cooked spinach that had been left standing at room temperature.