A method of increasing the lengths of telomeres in animal cells is practiced by administering an aqueous extract of an Uncaria species to an animal. The animal may be a human and the Uncaria species may be Uncaria tomentosa. Human subjects receiving a daily dose of an aqueous extract of Uncaria tomentosa for a sufficient period of time exhibited an increase in telomere length relative to a baseline measurement taken prior to treatment. The extract may be administered topically or systemically.
