vitamin · for high blood pressure
Niacin
Widens blood vessels and shifts your cholesterol balance in a better direction.
Say that in clinical terms
Increases prostaglandin-mediated vasodilation and improves lipid profile, reducing LDL and triglycerides while raising HDL.
How strong is the research?
2 papers read, 2 supporting.
Tested as: Extended-release niacin (e.g. Niaspan) at lipid-lowering doses (1–2 g/day), studied in dyslipidaemic patients
Who was studied: The big trials were in people with established heart disease or a previous heart attack.
How much to take
daily
500–2000 mg
Prescription niacin more studied than OTC. Monitor liver function at doses above 1500 mg/day.
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.
- At the recommended doses of 500–2,000 mg, niacin's vasodilatory effect can cause additive hypotension when combined with antihypertensive medications; patients seeking niacin for high blood pressure are disproportionately likely to already be on ACE inhibitors, ARBs, calcium channel blockers, or diuretics, making physician coordination essential before initiating pharmacologic niacin.
When to take it
Best taken: with food
What we make of it
NIH states plainly that niacin has no significant effect on blood pressure.
The detail
Niacin’s effects on cholesterol are well established pharmacology. On blood pressure specifically, the NIH Office of Dietary Supplements concludes there is no significant effect.