The acid is not listed as a legal compound by China’s drug authorities for use in humans, although it exists in Niuhuang, a dried gallstone found in cows that is used in Chinese medicine.

She’s not alone—for centuries, Chinese herbs have remained one of the oldest remedies for preventing and healing diseases, and they are especially known for their use in longevity.

More than 20 traditional Chinese medicine doctors in southern China are being investigated over a “longevity drink” they developed, claiming it could help people live to 120. Health ...