Blood NAD Tracks Heart Disease, Not Aging

Blood levels of NAD don't decline with age in healthy adults. That's the central finding of a Vilnius University study of 1,068 adults, published in Nature Metabolism. NAD, short for nicotinamide adenine dinucleotide, is a molecule every cell uses to produce energy. It's also the molecule behind a fast-growing market in supplements that promise to restore what aging supposedly takes away.

The team ran 1,340 NAD measurements on dried blood spot samples collected under standardized conditions. The group included healthy adults and people with chronic diseases. In healthy men, whole-blood NAD stayed stable across the age range. In healthy women, it rose slightly with age. Neither pattern matches the steady decline that animal studies found in muscle, brain and skin tissue, and that supplement marketing has carried over to people.

Disease changed the picture. Participants with cardiovascular disease had lower NAD levels, and the clearest gap showed up in people with hypertension. In the chronic-disease group, the healthy pattern broke down: NAD declined with age in men, and the increase seen in healthy women disappeared. The association tracks health status, not the calendar.

Dr. Dalius Ratautas, who led the research at Vilnius University, put the result directly. For years, the prevailing narrative has been that NAD declines as we age and therefore needs to be restored, he said. His team's findings suggest that isn't what happens in the blood of healthy adults. The open question he raised runs the other way: whether NAD levels can tell clinicians something about cardiovascular health.

The study doesn't show cause in either direction. Lower NAD could contribute to cardiovascular disease, result from it, or reflect some third factor underneath both. It also doesn't show that raising NAD with a supplement prevents or treats heart disease or hypertension. The authors state those limits themselves, and they matter for anyone reading the result as a reason to buy or to stop buying NMN or NR products.

A commentary published alongside the study adds a second caution. Stephen Gardell and Joseph Baur note that most of the NAD in whole blood sits inside red blood cells, which handle metabolism differently from muscle or brain cells. Blood NAD may never mirror tissue NAD. The Vilnius team answers that a blood biomarker doesn't need to copy tissue levels to be useful, since blood tests are exactly how medicine monitors most processes at scale. The next step is a test of prediction: whether a whole-blood NAD reading can flag cardiovascular risk before disease shows up.