Inclusion Criteria:  Biological men and women, aged from 18-64 years and healthy Not taking any medications (prescription and non-prescription) or dietary/herbal supplements known to alter the pharmacokinetics of either study drug or cinnamon constituents Willing to abstain from consuming dietary/herbal supplements and citrus juices for several weeks Willing to abstain from consuming caffeinated beverages or other caffeine-containing products the evening before and morning of the first day of a study arm Willing to abstain from consuming any alcoholic beverages for one day prior to any study day, during the 14-hour inpatient days, and for the outpatient visit(s) following the 14-hour visit Willing to use an acceptable method of contraception that does not include oral contraceptive pills or patches (such as abstinence, copper IUD, condom) Have the time to participate Written informed consent (and assent when applicable) obtained from subject or subject's legal representative and ability for the subject to comply with the requirements of the study  Exclusion Criteria:  Under the age of 18 or 65+ years Any current major illness or chronic illness such as (but not limited to) kidney disease, hepatic disease, diabetes mellitus, hypertension, coronary artery disease, chronic obstructive pulmonary disease, cancer, or HIV/AIDS History of anemia or any other significant hematologic disorder History of drug or alcohol addiction or major psychiatric illness Pregnant or nursing History of allergy to cinnamon, letrozole, or nicotine Taking concomitant medications, both prescription and non-prescription (including dietary supplements/herbal products), known to alter the pharmacokinetics of either study drug or cinnamon constituents Presence of a condition or abnormality that, in the opinion of the Investigator, would compromise the safety of the patient or the quality of the data Recreational drug use such as amphetamines, benzodiazepines, cocaine, marijuana, MDMA, opioids, and PCP History of intolerance to cinnamon Out-of-range clinical laboratory value that the study physician considers participation in the study a health risk