Vitamin B3 (Niacin)
What it does and why you need it
Niacin is the umbrella term for two related forms, nicotinic acid and nicotinamide, both of which the body converts to the coenzyme NAD that drives energy metabolism. The body can also make a small amount of niacin from tryptophan in dietary protein, which is why niacin requirements are usually given as "niacin equivalents" (the niacin in food plus the contribution from tryptophan).
Deficiency (pellagra) is essentially absent in modern UK life; it required the maize-heavy diets of historical southern Europe and parts of the southern US to appear at scale. Mild low intake can show up as fatigue and digestive issues.
Best food sources
Values per 100g from USDA SR Legacy and McCance and Widdowson 7th edition; the site's food entries currently store macros only.
| Food | Typical UK portion | Niacin per portion | % men's RNI |
|---|---|---|---|
| Tuna | 100g | around 18mg | 109% |
| Chicken, cooked | 100g | around 13mg | 79% |
| Peanuts | 30g (a small handful) | around 4mg | 24% |
| Beef, lean cut, cooked | 100g | around 6mg | 36% |
| Brown rice, cooked | 150g | around 4mg | 24% |
| Fortified breakfast cereal (UK label) | 30g | around 5mg, check the pack | around 30% |
UK reference intake by age and sex
UK Reference Nutrient Intake (RNI) for niacin is set by SACN (1991), expressed as niacin equivalents (NE).
| Group | Daily niacin (mg NE) |
|---|---|
| Babies, 0 to 6 months | 3 |
| Babies, 7 to 12 months | 4 to 5 |
| Children, 1 to 3 years | 8 |
| Children, 4 to 6 years | 11 |
| Children, 7 to 10 years | 12 |
| Boys, 11 to 14 years | 15 |
| Girls, 11 to 14 years | 12 |
| Adolescents, 15 to 18 years | Boys 18, Girls 14 |
| Men, 19 to 50 years (NHS-cited) | 16.5 |
| Women, 19 to 50 years (NHS-cited) | 13.2 |
| Adults 50+ | Men 16, Women 12 |
| Pregnancy | No increment |
| Breastfeeding | +2 (so about 15) |
Deficiency signs and who is at risk
Pellagra (severe niacin deficiency, with the "three Ds": dermatitis, diarrhoea, and dementia) is essentially absent from modern UK life. Milder low intake can present as fatigue, indigestion, mouth ulcers, and dry skin.
At higher risk in the UK
- Heavy alcohol use.
- Severe eating disorders or food insecurity.
- Rare metabolic disorders (Hartnup disease, carcinoid syndrome).
Too much: safe upper limit
Niacin from food is not a concern. The two supplement forms differ:
- Nicotinic acid can cause facial flushing, warmth, and tingling at doses as low as 50mg. At doses above 17mg per day from a supplement, NHS guidance warns of "flushing of the skin". At high prescription doses (used historically for cholesterol) it can affect the liver.
- Nicotinamide does not flush and is the form in most B-complex products. NHS guidance: 500mg or less of nicotinamide a day from supplements is unlikely to cause harm.
NHS combined supplement guidance: 17mg or less of nicotinic acid daily, or 500mg or less of nicotinamide daily, is unlikely to cause any harm.
Supplements and UK guidance
Routine niacin supplementation is not needed for healthy UK adults. B-complex products typically use nicotinamide to avoid the flushing reaction.
High-dose nicotinic acid was historically used to lower LDL cholesterol; that role has been largely taken over by statins and is no longer routine NHS prescribing.
Related
- Also used as a food additive: E375 nicotinic acid.
- The B-vitamin family: Vitamin B1, Vitamin B2, Vitamin B6, Folate, Vitamin B12.
- Best food sources: Tuna, Chicken, Beef, Peanuts.
Sources and references
- NHS. Vitamins and minerals: Vitamins B. nhs.uk/conditions/vitamins-and-minerals/vitamin-b.
- SACN. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Department of Health Report 41 (1991).
- Public Health England. McCance and Widdowson's The Composition of Foods, 7th summary edition (2015).
This page is reference information for UK shoppers. It is not medical advice.