The NAD+ study every APOE4 carrier needs to see (and the warning they buried)

The researchers behind the December 2025 Cell Reports Medicine NAD+ study issued a direct warning that current over-the-counter NAD+ precursors (NMN and NR) have been shown in animal models to raise cellular NAD+ to dangerously high levels that promote cancer. Their mechanism with P7C3-A20 is fundamentally different because it activates NAMPT and lets cells maintain homeostatic NAD+ balance, rather than flooding them with precursors that bypass regulation. One human trial (Wu et al. 2025) did show 8 weeks of NR at 1g per day reduced pTau217 by 7 percent versus an 18 percent increase in placebo, so the picture is nuanced. Long-term safety data does not yet exist. APOE4 carriers considering NMN or NR should discuss cancer risk factors with their physician before starting.

Researchers at Case Western Reserve University and University Hospitals used P7C3-A20, a compound that activates NAMPT (the rate-limiting enzyme in NAD+ recycling), and fully reversed cognitive deficits in mice with advanced Alzheimer's disease. Both mouse lines recovered cognitive function. The treatment also reversed tau phosphorylation, blood-brain barrier deterioration, oxidative stress, DNA damage, and neuroinflammation. Critically, the researchers identified 46 proteins that were abnormally expressed in Alzheimer's mouse brains and normalized by treatment, and the same proteins show similar alterations in human Alzheimer's brains. This challenges the century-old dogma that Alzheimer's is intrinsically irreversible.

NDAN stands for Non-Demented with Alzheimer's Neuropathology, a population whose brains at autopsy show full Alzheimer's pathology (amyloid plaques and tau tangles) but who remained cognitively sharp throughout life. The December 2025 NAD+ study suggests preserved NAD+ homeostasis is one key answer: NAD+ appears to function as a resilience factor that protects cognitive function even when disease pathology is present. For APOE4 carriers, this reframes the goal from preventing amyloid accumulation to building metabolic resilience that protects cognition regardless of pathology. APOE4 carriers experience accelerated metabolic dysfunction and faster NAD+ decline, making resilience-building especially relevant.

Exercise is the most powerful evidence-based NAD+ intervention available, and it works through the exact same NAMPT pathway that P7C3-A20 targets. Both aerobic training and resistance training increase NAMPT expression, and NAMPT levels are positively correlated with lean body mass and VO2 max. Additional natural strategies include periodic fasting or time-restricted eating (which activates NAD+ recycling), adequate sleep (NAD+ is consumed repairing DNA damage, including damage from poor sleep), and limiting alcohol (which depletes NAD+ during metabolism). These strategies support NAD+ through homeostatic pathways rather than forcing supraphysiologic levels.

In the Alzheimer's mouse models used in the December 2025 study, NAD+ levels declined 30 percent by 6 months of age and 45 percent by one year, a dramatic drop that preceded cognitive decline. This suggests NAD+ depletion is not just a downstream consequence of neurodegeneration but may be an upstream driver. For APOE4 carriers, who already experience accelerated metabolic dysfunction, tracking and supporting NAD+ proactively (through exercise, sleep, and fasting) becomes a high-priority intervention rather than a wait-and-see one.

The research, published in Cell Reports Medicine on December 22, 2025, represents something we rarely see in Alzheimer's research: full reversal of cognitive deficits in advanced disease models. The research team at Case Western Reserve University and University Hospitals used a compound called P7C3-A20, which activates an enzyme called NAMPT — the rate-limiting enzyme in your body's NAD+ recycling pathway. Here's what they discovered: In mice with advanced Alzheimer's disease , treatment with P7C3-A20 fully reversed cognitive deficits. Not slowed. Not stabilized. Reversed. According to the researchers, "both lines of mice fully recovered cognitive function." The treatment addressed multiple disease processes simultaneously — reversing tau phosphorylation, blood-brain barrier deterioration, oxidative stress, DNA damage, and neuroinflammation. Perhaps most significantly for translation to humans, the researchers identified 46 proteins that were abnormally expressed in the Alzheimer's mouse brain and normalized by treatment — and these same proteins show similar alterations in human Alzheimer's brains. This suggests the mechanism might actually work in human brains. KEY INSIGHT: This study looked at NAD+ levels in mice at different disease stages. NAD+ declined 30% at 6 months and 45% by one year in Alzheimer's models — a dramatic drop that preceded cognitive decline.

Don't panic and stop immediately — that's not what the research suggests Have a conversation with your doctor about these findings Consider whether the potential risks align with your personal health situation (especially important if you have cancer risk factors) Explore the natural NAD+ support strategies below as complementary or alternative approaches