High-fat meal (HFM) consumption increases oxidative stress in humans. The metabolic cofactor nicotinamide adenine dinucleotide (NAD+), has been identified as a key regulator of oxidative stress. Older individuals suffer from low NAD+ levels and experience age-related increases in oxidative stress. Nicotinamide Riboside (NR), a newly discovered NAD+ precursor has demonstrated the ability to raise NAD+ in older adults. Nicotinic Acid (NA), another NAD+ precursor is established as one of the oldest anti-atherogenic supplements that improves vascular function. Similarities between NR and NA indicate NR may have potential vascular benefits yet to be discovered. We hypothesized that one week of NR supplementation would reduce postprandial oxidative stress and improve vascular function following consumption of a HFM (1050 kcal, 72g fat) in old and young participants...One week of NR supplementation was well tolerated in all participants but had no effect on postprandial oxidative stress and microvascular function.