vitamin · for afternoon energy crash
Niacin
Raises NAD, which your cells use to release energy from food all day.
Say that in clinical terms
NAD+ precursor essential for glycolysis, TCA cycle, and oxidative phosphorylation, maintaining cellular energy throughout the day.
How strong is the research?
1 paper read.
Who was studied: The trial used a different NAD precursor in healthy middle-aged adults. Niacin itself has not been tested for this.
No randomized controlled trials were found testing niacin (nicotinic acid specifically) for fatigue or energy outcomes as a primary endpoint in humans. PubMed searches with the RCT filter returned results about niacin for cardiovascular outcomes (lipids, endothelial function), with fatigue appearing only as a reported side effect rather than an outcome being treated. The only fatigue-directed NAD-precursor trials found use nicotinamide mononucleotide (NMN, PMID 35215405) or nicotinamide riboside (NR), both of which are chemically distinct from nicotinic acid. 'Afternoon energy crash' has no recognized clinical equivalent term ('postprandial somnolence' is used for drowsiness but no trials co
How much to take
daily
100–500 mg
Niacinamide form avoids flushing. Sustained-release forms may cause liver stress at high doses.
Before you take it
- NIH ODS Tolerable Upper Intake Level (UL) for adults 19+ is 35 mg/day of supplemental nicotinic acid (niacin); this UL does not apply to niacin used under medical supervision.
- Nicotinic acid at 30–50 mg or higher typically causes flushing (skin redness, burning, itching within 15–30 minutes of ingestion); the most common cause of self-discontinuation at supplement doses.
- Pharmacologic doses of 1,000–3,000 mg/day can cause hepatotoxicity over months to years; extended-release formulations carry higher hepatotoxic risk than immediate-release formulations at equivalent doses.
- Doses of 1,500 mg/day or higher induce insulin resistance and increase hepatic glucose production, raising blood glucose; patients with diabetes or pre-diabetes require medical supervision before use.
- High-dose nicotinic acid therapy (≥1,000 mg/day) is associated with hypotension and fall risk.
- Isoniazid and pyrazinamide (tuberculosis medications) block tryptophan-to-nicotinic acid conversion, increasing pellagra risk in co-exposed patients.
- High-dose niacin used alongside antidiabetic medications requires dose monitoring due to niacin-induced blood glucose elevation.
- HPS2-THRIVE (n=25,673 RCT, Merck-funded): Extended-release niacin combined with laropiprant added to statin therapy was associated with significantly increased serious infections, myopathy (including rhabdomyolysis), and bleeding events.
- Nicotinamide (niacinamide) is a chemically distinct B3 form that does not cause flushing and has a different pharmacological and safety profile; the flushing and hepatotoxicity concerns above apply specifically to nicotinic acid, not nicotinamide.
When to take it
Best taken: with food
What we make of it
The trial used a different form of B3, and its energy findings were negative.
The detail
The study tested nicotinamide riboside, which is a different B3 compound — evidence for one does not carry to the other. And its energy results were negative: NAD levels rose, but resting energy use, fat burning, endurance and movement all stayed the same. No trial of niacin or NR has ever measured an afternoon energy crash, which is not a recognised clinical outcome.