BAKERSFIELD, Calif. -- Alzheimer's disease currently affects 5 million Americans, and that number is projected to rise.

Finding a way to improve memory and delay dementia's onset is a major public health goal. Small studies have suggested that perhaps ginkgo biloba extract may be able to fight dementia in elderly patients, but the theory has never been properly tested until now.

Researchers at the University of Virginia School of Medicine studied more than 3,000 seniors over the age of 75. They found that those taking ginkgo supplements twice a day for six years had no lower chance of developing dementia than those who took a placebo.

Ginkgo also did not help memory in a subset of patients who already had mild cognitive impairments.

The hunt goes on for a molecule that will help, and the goal is to find a treatment that can delay dementia for 10 years.