The goal of the study is to determine the acute and short-term supplementation effect of a commercially available theacrine-containing supplement (NAD3) on numbers of various circulating stem cell populations in older adults.

This is a double-blind, placebo-controlled crossover study with 12 participants randomized to receive either NAD3® or a placebo for seven days. Blood samples are collected after an overnight fast, before and after the seven-day supplementation period, as well as one and two hours after the final supplement/placebo dose. Using flow cytometry, circulating stem cells, including lymphocytoid CD34+ stem cells (CD45dimCD34+), stem cells associated with vascular maintenance and repair (CD45dimCD34+CD309+), CD34+ stem cells linked to a progenitor phenotype (CD45dimCD34+CD309neg), circulating endothelial stem cells (CD45negCD31+CD309+), and mesenchymal stem cells (CD45negCD90+) are quantified.

Inclusion Criteria:

• Male or Female
• Age 40-70
• BMI between 21-34.99 kg/m2
• Vital signs with in normal range (heart rate 60-100 beats/minute, blood pressure (40-44 years - 125/83, 45-49 years- 127/84, 50-54 years -129/85, 55-59 years - 131/86, >60 - 134/87), 36.4-37.4 degrees Celsius
• Sedentary to lightly active (2 or fewer days per week of exercise)

Exclusion Criteria:

• Female participants who are lactating, pregnant or planning to become pregnant during the study
• History of use of illicit drugs or other substances of abuse within 12 months of the screening visit (to be determined at screening)
• Tobacco during the 90 days prior to screening
• Current use of medication/dietary supplements that claim to or have an effect on age-related processes, e.g. "anti-aging" supplements. Participants must undergo a ≥7-day washout period of no supplementation to be eligible.
• Known allergy, intolerance or hypersensitivity to NAD3
• Self-reported active infection or illness of any kind
• Cognitively impaired and/or unable to give informed consent