Also known as: Niacin, Nicotinic acid, Nicotinamide, Niacinamide, Inositol hexanicotinate, NAD precursor
VitaminsStrong evidence
A precursor to NAD, the coenzyme behind most of the body's energy production. The form matters more here than for any other B vitamin, because one version causes an alarming flush and the other does not.
Typical dose
16.0–50.0 mg per day
With food; nicotinic acid on an empty stomach maximises the flush
What it is
Vitamin B3 exists in two main forms that behave quite differently. Nicotinic acid is the form that causes flushing. Nicotinamide, also called niacinamide, does not flush but also lacks some of nicotinic acid's other effects.
A third form, inositol hexanicotinate, is sold as no-flush niacin. It does avoid the flush, largely because it releases very little nicotinic acid, which means it also does not do what nicotinic acid does. It is a reasonable choice only if you want B3 without any of the flushing effects.
Unusually among vitamins, the body can make niacin from tryptophan, at roughly 60 mg of tryptophan to 1 mg of niacin, which is why adequate protein intake contributes to B3 status. Sources include meat, fish, wholegrains and legumes.
How it works
Both forms convert to NAD and NADP, coenzymes involved in several hundred reactions, including the electron transport chain that produces most cellular ATP. NAD is also consumed by enzymes involved in DNA repair and metabolic regulation.
This is the same coenzyme that NMN and nicotinamide riboside target, at considerably greater expense. Plain nicotinamide raises NAD effectively and costs very little, which is a comparison the longevity category tends not to draw attention to.
The flush is a separate mechanism entirely. Nicotinic acid triggers release of prostaglandins in the skin, causing blood vessels to widen. The result is intense redness, heat and tingling across the face and upper body, starting within 20 minutes and lasting up to an hour. It is harmless, genuinely uncomfortable, and alarming if you were not expecting it.
What the evidence shows
B3's essentiality is beyond question, and shortfall is rare in the UK given how widely it occurs in food and the contribution from tryptophan.
Nicotinic acid at gram doses has well-documented effects on blood lipid markers, and has been used that way under medical supervision for decades. Those are pharmacological doses with real monitoring requirements, not a supplement application, and self-dosing at that level is not sensible.
For energy or performance in people with adequate intake, there is no meaningful evidence of benefit. As with the other B vitamins, B3 enables energy production rather than increasing it.
Dosing
Reference intakes are around 16 mg daily for men and 14 mg for women, which ordinary food covers.
For general supplementation, choose nicotinamide. It supports NAD without the flush and is well tolerated at typical supplemental doses of 20-50 mg.
If you take nicotinic acid, expect the flush. It is reduced by taking it with food, starting at a low dose and building up, and it lessens with regular use. Gram-level doses belong under medical supervision because of the monitoring involved, not because a supplement label says so. Avoid taking nicotinic acid on an empty stomach unless you want the full experience.
Flush begins within 20 minutes and resolves within an hour; NAD effects accrue with regular intake
Timing
With food; nicotinic acid on an empty stomach maximises the flush
Competition status
Permitted — not on the WADA Prohibited List
Category
Vitamins
Safety and side effects
At intakes from food and ordinary supplements, B3 is safe. The flush from nicotinic acid is harmless but genuinely uncomfortable and is the most common reason people stop taking it.
High doses are a different matter. Sustained gram-level intake of nicotinic acid can affect the liver, and sustained-release preparations appear more likely to do so than immediate-release. This is why gram doses warrant supervision and monitoring rather than self-management.
High-dose nicotinic acid may also raise blood sugar and uric acid. Speak to your doctor before taking anything above ordinary supplemental amounts, particularly if you take regular medication.
Who should avoid it
Do not take gram-level doses without medical supervision and monitoring. Speak to your doctor before use if you take regular medication, if your blood sugar or uric acid is being monitored, or if you have been told your liver is not working normally. Expect flushing with nicotinic acid; choose nicotinamide to avoid it.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
