The New Complete Book of Food
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.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.
Nitrates. Like beets, celery, eggplant, lettuce, radishes, and spinach, greens contain 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 car-
cinogens, 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 tempera-
ture, 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.Food/Drug Interactions
Anticoagulants Greens are rich in vitamin K, the blood-clotting vitamin produced natu-
rally by bacteria in the intestines. Consuming large quantities of this food may reduce the
effectiveness of anticoagulants (blood thinners) such as warfarin (Coumadin). One cup of
drained, boiled fresh kale, for example, contains 1,062 mcg vitamin K, nearly 200 times the
RDA for a healthy adult.