Metabolism, like other
aspects of life, involves tradeoffs. Oxidant
by-products of normal metabolism cause
extensive damage to DNA, protein, and
lipid. We argue that this damage (the same
as that produced by radiation) is a major
contributor to aging and to degenerative
diseases of aging such as cancer, cardiovascular
disease, immune-system decline,
brain dysfunction, and cataracts. Antioxidant
defenses against this damage include
ascorbate, tocopherol, and carotenoids.
Dietary fruits and vegetables are the principal
source of ascorbate and carotenoids
and are one source of tocopherol. Low
dietary intake of fruits and vegetables doubles
the risk of most types of cancer as
compared to high intake and also markedly
increases the risk of heart dise and
cataracts. Since only 9% of Americans eat
the recommended five servings of fruits
and vegetables per day, the opportunity
for improving health by improving diet is
great.