NAD⁺ crash and the metabolic aftermath
Both enzymatic steps in ethanol metabolism consume NAD⁺. By the end of a drinking session the NAD⁺/NADH ratio is profoundly inverted, and most of what feels like "still hungover" the next day is the metabolic shadow of that crash, not residual acetaldehyde.
What is happening
Alcohol dehydrogenase converts ethanol to acetaldehyde, consuming NAD⁺ → NADH. ALDH2 then converts acetaldehyde to acetate, again consuming NAD⁺ → NADH. Two NAD⁺ molecules per ethanol molecule, several drinks an hour, several hours of drinking — the salvage pathway cannot keep up. The NAD⁺/NADH ratio drops by an order of magnitude in the hepatocyte cytosol and is still depressed the next morning.
The downstream consequences are the morning-after experience for most people: gluconeogenesis stalls (low NAD⁺ blocks the malate-aspartate shuttle, so the liver cannot make glucose efficiently — hence the fatigue and the carbohydrate craving), fatty acid oxidation reverses toward synthesis (the "fatty liver" of acute drinking), and SIRT3 — the NAD⁺-dependent deacetylase that activates ALDH2 — runs out of substrate, throttling clearance even when ALDH2 enzyme is abundant.
Ingredients that address this, ranked
- Nicotinamide Riboside (NR) Tier 1 · Core Impact: high — Direct NAD⁺ precursor via the salvage pathway. Restores cofactor availability for ALDH2, SIRT3, and gluconeogenesis.
- Benfotiamine Tier 2 · Strong Impact: medium — Restores TPP cofactor pool for the parallel TCA-cycle enzymes that NAD⁺ also feeds.
How tiers compare for this mechanism
| Goal | Best (Tier 1) | Strong support (Tier 2) | Situational (Tier 3+) |
|---|---|---|---|
| NAD⁺ pool restoration | NR | ||
| ALDH2 cofactor support | NR | ||
| TCA / gluconeogenesis cofactors | Benfotiamine | ||
| SIRT3 substrate | NR |
Deeper science · In more detail
Why NR specifically
Niacin (NAD), nicotinamide, and nicotinamide riboside all feed the NAD⁺ salvage pathway, but NR has the cleanest human pharmacokinetic data (Trammell 2016) and the cleanest human safety record (Martens 2018, Conze 2019). NMN is a viable alternative at equal molar dose. Plain niacin works but causes flushing at meaningful doses. The protocol picks NR because the dose-to-NAD⁺ relationship is documented in human plasma rather than inferred.
Why this is the cofactor side of the same problem
The acetaldehyde clearance story and the NAD⁺ story are not separate. ALDH2 is rate-limited by NAD⁺ availability — when the NAD⁺ pool is depressed, the enzyme throttles even when present in normal abundance. Supporting NAD⁺ supports clearance. This is why the acetaldehyde page places NR in Tier 1 alongside NAC and Sulforaphane: it is upstream of the rate-limiter, not parallel to it.
Why the symptoms persist into morning
Acetaldehyde clears in hours; the NAD⁺ pool takes substantially longer to restore from baseline biosynthesis alone. The "fog and fatigue" most people associate with morning hangover is mostly the lag between acetaldehyde clearance (fast) and NAD⁺ pool recovery (slow). Supporting the salvage pathway compresses that lag.