It may take more than a spoonful of sugar to help Dr. Leila Denmark's brand of medicine go down. "When a mother asks, 'Doctor, what makes my baby so bad?' " she reports, "I'll say, 'Go look in the mirror. You get apples off apple trees.' "

After 70 years on the job, pediatrician Denmark, who turned 100 in February, making her the country's most senior medical citizen, can afford to dispense her frank advice in large doses. That back-to-basics approach is what fills the waiting room of her office in Alpharetta, Ga., up to 10 hours a day, six days a week. "She's been in practice so long," says Denise Jacob, mother of two small patients, "she can look at a child and tell you what's wrong."

In fact, Denmark, who graduated from the Medical College of Georgia in 1928 and helped develop a vaccine for whooping cough in the '30s, was practicing holistic medicine long before its return to vogue. "She always focused on family and its relationship to the wellness of a child," says Dr. David Jones, 45, an old friend.

The third of 12 children of a Portal, Ga., farmer and his wife, Denmark practiced medicine at home while raising her only child, Mary, now 67. The secret of her longevity is simple, says the great-grandmother of two: "I eat vegetables and protein at every meal, and I love what I'm doing." She thought of quitting once—when husband John Denmark, a Federal Reserve Bank executive, died in 1990, at 91—but reconsidered. "When I can't see or think well, I'll quit," she says. "And when I go, I hope it will be right here in this office."

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