Functional foods that contain significant amounts of bioactive
components may provide desirable health benefits beyond basic
nutrition and play important roles in the prevention of chronic
diseases. The key question is whether a purified phytochemical
has the same health benefit as does the whole food or mixture of
foods in which the phytochemical is present. Our group found,
for example, that the vitamin C in apples with skin accounts for
only 0.4% of the total antioxidant activity, suggesting that most
of the antioxidant activity of fruit and vegetables may come from
phenolics and flavonoids in apples. We propose that the additive
and synergistic effects of phytochemicals in fruit and vegetables
are responsible for their potent antioxidant and anticancer activities,
and that the benefit of a diet rich in fruit and vegetables is
attributed to the complex mixture of phytochemicals present in
whole foods.