IV Administration of ChromaDex's Niagen® as Compared to NAD+

Inclusion Criteria: * Provision of signed and dated informed consent form * Stated willingness and demonstrated ability to comply with all study procedures, as well as availability for the duration of the study * Lives within 100 miles of a NRI study site * Any gender, aged 40+ (For the 5th arm, only males will be evaluated.) * Good general health as evidenced by medical history * For females of reproductive potential: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation and for an additional month after the end of the study * Agreement to adhere to Lifestyle Considerations throughout study duration Exclusion Criteria: * Current diagnosis of any seizure disorder, diabetes or insulin resistance, any kidney or liver disorder, heart disease, cancer, or Parkinson's disease, * Pregnancy, trying to conceive, or breastfeeding * Known allergic reactions to any components of the intervention * Positive COVID-19 test within 30 days of the study period * Recent dramatic weight changes (10% change in body weight in the last 6 months) * Existing usage of a NAD+ or NAD precursor supplement in any form. * Introducing a new investigational drug or other intervention within 30 days before the start of the study