@kristisawicki: There’s a new 2026 paper in Nature Metabolism titled: “Whole-blood NAD+ levels do not reflect healthy ageing.” And social media is already turning this into: “See? NAD doesn’t decline with age.” “NAD supplements are pointless.” But that is NOT what this paper showed. Here’s what the researchers actually found: They measured NAD+ levels in WHOLE BLOOD and found that blood NAD+ levels did not consistently decline with age. Their conclusion? Whole-blood NAD+ is likely NOT a reliable biomarker for healthy aging. That’s very different from saying NAD+ inside tissues or cells does not decline with age. NAD+ does its real work INSIDE cells: • mitochondria • muscle • brain • liver • immune cells And this paper did not directly measure intracellular NAD+ in those tissues. This is something I’ve talked about before: Commercial blood NAD tests are probably not very useful because blood may not reflect what’s happening inside tissues. But that does NOT automatically mean: • tissue NAD+ stays stable with age • mitochondrial NAD+ is unaffected • supplementation is useless In fact, multiple published studies still show age-related NAD+ decline in tissues, especially in muscle, liver, and mitochondrial compartments. What this paper really tells us is: A simple blood draw may not be a good way to assess NAD biology or “biological age.” And honestly… that’s not surprising. A lot of aging biology is compartment-specific. What’s happening inside mitochondria often does NOT show up clearly in circulation. So this paper is really more about the limitations of blood biomarkers than it is a “debunking” of NAD decline or NAD research altogether. Science is nuanced. One paper rarely overturns an entire body of literature.

Dr. Kristi Sawicki, Ph.D.

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Saturday 30 May 2026 19:08:49 GMT