ANAHEIM, Calif. - If you had any remaining doubts about the popularity of organic and so-called natural foods, a visit to the Anaheim Convention Center here last week would have dispelled them. Inside its five vast halls, more than 3,000 exhibitors showed their wares to some 77,000 retailers, suppliers, investors and curiosity-seekers as part of the Natural Products Expo West, known among foodies as simply Expo West.