An Approach to Cellular Energy and Brain Health
At Rezilir Health, optimizing cellular energy is foundational to how we approach brain health, longevity, and recovery. One molecule at the center of this conversation is NAD⁺ (nicotinamide adenine dinucleotide). But not all NAD-focused therapies are the same. Two of the most discussed options today are NAD IV and Niagen IV (nicotinamide riboside). While they aim to support the same system, their mechanisms, tolerability, and evidence base differ in important ways.
Why NAD⁺ Matters for Brain Health
NAD⁺ is a critical coenzyme involved in mitochondrial energy production (ATP), DNA repair and cellular resilience, and activation of sirtuins which are proteins linked to aging and neuroprotection. Declining NAD⁺ levels have been associated with cognitive decline, neurodegenerative processes, chronic fatigue and burnout and impaired stress resilience. NAD IV therapy delivers NAD⁺ directly into the bloodstream, with the goal of rapidly increasing systemic levels.
Advantages of having NAD IV include that it bypasses digestion and has direct systemic exposure. Clinical limitations are long infusion times due to potential side effect of GI upset, flushing, anxiety and uncertain intracellular uptake. From a mechanistic standpoint, NAD⁺ is a large molecule, and emerging evidence suggests it may not efficiently enter cells intact. Instead, it may need to be broken down first—raising questions about how much of the infused NAD⁺ is actually utilized at the cellular level.
What Is Niagen IV?
Niagen IV uses nicotinamide riboside (NR), a precursor to NAD⁺ and a form of vitamin B3. Rather than delivering NAD⁺ directly, Niagen enters the cells efficiently and ss converted into NAD⁺ through natural metabolic pathways. This aligns more closely with how the body physiologically produces NAD⁺.
Niagen IV vs. NAD IV: Key Differences
Niagen IV (nicotinamide riboside) and NAD IV both aim to boost NAD⁺ levels, but they differ in how they work and how they’re tolerated. NAD IV delivers NAD⁺ directly into the bloodstream, often requiring longer infusion times and sometimes causing side effects like nausea or chest tightness. In contrast, Niagen IV provides a precursor that cells convert into NAD⁺ internally, which is generally better tolerated and allows for shorter infusions. While Niagen’s mechanism is considered more biologically efficient, especially for cellular uptake, most clinical evidence supports oral NR rather than IV use, and both approaches still lack strong, standardized research for many wellness claims.
What Does the Evidence Show?
The evidence around IV NAD⁺ therapies is still developing, but a few key points are emerging. Niagen IV appears to be better tolerated than traditional NAD⁺ infusions which can make a meaningful difference for patients already dealing with fatigue or neurologic sensitivity. Niagen also works through well-understood cellular pathways to increase NAD⁺ levels, suggesting that supporting the body’s own production may be more effective than delivering NAD⁺ directly. From a clinical perspective, NAD⁺ optimization works best as part of a comprehensive plan that includes sleep, nutrition, stress management, and addressing underlying inflammation.
While both NAD IV and Niagen IV target the same longevity pathway, they are not equivalent in practice. Niagen IV (nicotinamide riboside) offers a more physiologic, better-tolerated, and clinically practical approach, whereas NAD IV, though widely used, raises ongoing questions around cellular utilization and side effects. As longevity science continues to evolve, the focus should be not just on increasing NAD⁺ levels, but on doing so in a way that is effective, well-tolerated, and aligned with human biology. Niagen IV represents a promising step in that direction, though continued research will help clarify its optimal role in clinical care.
References:
Reyna K, et al. Intravenous infusion of NAD⁺ versus nicotinamide riboside: a retrospective tolerability pilot study. Frontiers in Aging. 2026.
Hawkins J, et al. Randomized, placebo-controlled pilot study of NR IV vs NAD IV. 2024.
