Let me put this in terms that actually mean something. When researchers at the University of Washington measured NAD+ levels across age groups, the numbers were brutal. By age 50, most people have lost roughly half the NAD+ they had at 20. By 70, they're running on fumes — sometimes 10-20% of youthful levels. This isn't some obscure biomarker that doesn't affect daily life. Low NAD+ means your DNA repair machinery slows to a crawl. It means your mitochondria can't produce energy efficiently. It means your cells start accumulating damage they used to clear effortlessly. That creeping fatigue, the slower recovery, the fog that wasn't there ten years ago — a lot of it traces back to this one molecule.
The supplement industry figured this out about five years ago and promptly turned it into a circus. Every brand now claims their NAD+ booster is the breakthrough of the century. Most of them are garbage. The actual science narrows the field to two serious contenders: NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside). Both are precursors — your body converts them into NAD+. NMN is one step closer to NAD+ in the biosynthetic pathway, which is why David Sinclair and most longevity researchers personally take it. NR has more published human clinical trials, including a landmark 2018 study showing it raised NAD+ levels by 60% in older adults at 1,000mg daily.
Here's where it gets interesting. A 2023 trial at Washington University gave 250mg of NMN daily to adults over 55 and measured not just NAD+ levels but actual physical outcomes. Walking speed improved. Muscle insulin sensitivity improved. These weren't just numbers on a lab report — they were real functional gains in people who were already declining. The placebo group? They kept declining. That's the part that should make you pay attention. Doing nothing isn't neutral. Doing nothing means you're actively getting worse.
The debate between NMN and NR is real, but it's also a bit of a distraction. Both raise NAD+. Both have clinical evidence. The more important questions are: what dose, what purity, and how are you taking it? Sublingual NMN absorbs faster than capsules. Third-party tested NMN is non-negotiable because the market is flooded with underdosed products. And if you're taking less than 250mg daily, you're probably below the therapeutic threshold that the clinical trials used. The studies that showed real results weren't using the cute 125mg "starter doses" that most brands sell.
There's a clock running inside every cell in your body, and NAD+ is what keeps it ticking accurately. You can't feel it dropping — not directly. You just feel a little more tired, a little slower, a little less sharp. And one day you realize you've been blaming everything else — stress, sleep, work — when the real problem was biochemical all along. The good news is that NAD+ levels are one of the few aging biomarkers we can actually push back up. The question is whether you'll do it now, or wait until there's less to salvage.
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