long-running Harvard School of Public Health/Health Professionals Follow-Up Study of male
doctors showed that a diet rich in high-potassium foods such as bananas, oranges, and plantain
may reduce the risk of stroke. In the study, the men who ate the higher number of potassium-
rich foods (an average of nine servings a day) had a risk of stroke 38 percent lower than that of
men who consumed fewer than four servings a day. In 2008, a similar survey at the Queen’s
Medical Center (Honolulu) showed a similar protective effect among men and women using
diuretic drugs (medicines that increase urination and thus the loss of potassium).
Protection against some cancers. According to the American Cancer Society, a diet high in
foods rich in antioxidant vitamin C may reduce your risk of some cancers, such as cancer of
the respiratory tract. In addition, oranges contain D-limonene, an aromatic compound found
in citrus oils. D-limonene is a monoterpene, a member of a family of chemicals that appears
to reduce the risk of some cancers, perhaps by preventing the formation of carcinogens in
your body or by blocking carcinogens from reaching or reacting with sensitive body tissues
or by inhibiting the transformation of healthy cells to malignant ones.
Lower risk of some birth defects. Up to two of every 1,000 babies born in the United States
each year may have cleft palate or a neural tube (spinal cord) defect due to their mothers’ 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 a folate supplement before becoming preg-
nant and 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.
Potassium benefits. Because potassium is excreted in urine, potassium-rich foods are often
recommended for people taking diuretics. In addition, a diet rich in potassium (from food)
is associated with a lower risk of stroke. A 1998 Harvard School of Public Health analysis
of data from the long-running Health Professionals Study shows 38 percent fewer strokes
among men who ate nine servings of high potassium foods a day vs. those who ate fewer
than four servings. Among men with high blood pressure, taking a daily 1,000 mg potas-
sium supplement—about the amount of potassium in two cups orange juice—reduced the
incidence of stroke by 60 percent.
Antiscorbutics. All citrus fruits are excellent sources of vitamin C, used to cure or prevent
the vitamin C–deficiency disease scurvy. Your body also needs vitamin C in order to convert
the amino acid proline into hydroxyproline, an essential ingredient in collagen, the protein
needed to form skin, tendons, and bones. People with scurvy do not heal quickly, a condition
that can be cured by feeding them foods rich in vitamin C. Whether taking extra vitamin
C speeds healing in healthy people remains to be proved. Oranges and other citrus fruits
also contain rutin, hesperidin, and other natural chemicals known collectively as flavonoids
(“bioflavonoids”). In experiments with laboratory animals, flavonoids appear to strengthen
capillaries, the tiny blood vessels just under the skin. To date this effect has not been dem-
onstrated in human beings.
Enhanced absorption of iron from plant foods. Nonheme iron, the inorganic form of iron found
in plant foods, is poorly absorbed by the body because it is bound into insoluble compounds
Oranges