Niacin, vitamin B3 explained.

Quick answer. Niacin is vitamin B3. It comes in 2 forms, nicotinic acid and nicotinamide, and the NHS lists meat, fish, wheat flour and eggs as good sources. In the UK government's food composition data (CoFID 2021), grilled skinless chicken breast has 15.8mg of niacin per 100g, roasted lean pork loin 12.5mg and tuna canned in brine 10.3mg. The NHS says adults need about 16.5mg a day (men) or 13.2mg (women), and that most people get it from their diet.

What foods are high in niacin?

The NHS page on B vitamins names 4 good sources of niacin: meat, fish, wheat flour and eggs.

The Composition of Foods Integrated Dataset (CoFID), the UK government's food composition tables, gives the figures. It lists 2 numbers for each food: niacin itself, and the niacin equivalent, which also counts what the body can make from protein (explained below). Both columns are from the 2021 release, per 100g of the food as described.

Per 100g, grilled chicken breast and fortified cornflakes each carry 99% of the 16mg nutrient reference value (NRV) in niacin alone, and tuna 64% (calculated). Fortified cereals vary by brand, so check the pack. Wholemeal flour carries about three times the niacin of white plain flour, which CoFID lists at 1.7mg.

What is niacin?

Niacin is also known as vitamin B3. The NHS says "There are 2 forms of niacin: nicotinic acid and nicotinamide. Both are found in food." It says niacin helps "the body release energy from food", and it names the nervous system and skin as the other areas where niacin plays a part.

The NHS also notes that "Niacin cannot be stored in the body, so you need it in your diet every day." Because it sits in meat, fish, bread and cereals, most people eating a mixed diet take in some at almost every meal.

What is a niacin equivalent?

The body has a second route to niacin. CoFID's user guide describes one of its columns as "Potential nicotinic acid from the amino acid tryptophan, calculated as tryptophan divided by 60." Tryptophan is an amino acid found in protein.

The UK government's dietary recommendations then define the total: "Niacin equivalent = niacin + (tryptophan divided by 60)". The government's daily figures for adults, the same 16.5mg and 13.2mg the NHS quotes, are niacin equivalents.

Eggs show why it matters. CoFID measures only 0.1mg of niacin in 100g of boiled egg, but 3.7mg of niacin equivalent once the tryptophan is counted. Milk (0.1mg of niacin, 0.7mg of niacin equivalent) and Cheddar (0.1mg and 6.9mg) work the same way.

How much niacin do I need a day?

The NHS says the amount of niacin you need is about 16.5mg a day for men and 13.2mg for women. The government's dietary recommendations give those figures for adults aged 19 to 64, and slightly lower ones later in life: 15.5mg (men) and 12.6mg (women) at 65 to 74, and 15.1mg and 12.1mg from 75.

Food labels use one figure for everyone, the NRV, which is 16mg for niacin. Our explainer on what NRV means covers how the label figure relates to the NHS amounts.

The NHS says "You should be able to get all the niacin you need from your daily diet." Taken from the table, 100g of grilled chicken breast and 100g of wholemeal bread give 19.6mg of niacin before any tryptophan is counted (calculated).

Can you take too much niacin?

The NHS cautions are about supplements, and the 2 forms are handled differently. The NHS says "Taking high doses of nicotinic acid supplements can cause skin flushes", and that there is not enough evidence on high daily doses of nicotinamide.

Its Department of Health and Social Care advice gives a separate figure for each form: "Taking 17mg or less of nicotinic acid supplements a day, or 500mg or less of nicotinamide supplements a day, is unlikely to cause any harm."

If you take more than one supplement, add up the niacin across them and check which form each label lists. For anything beyond diet, ask a GP or pharmacist.

What does niacin do?

In Great Britain, the wording a food or supplement may use about a nutrient comes from the GB nutrition and health claims register. These are the authorised claims for niacin that we use:

• Niacin contributes to normal energy-yielding metabolism.
• Niacin contributes to the reduction of tiredness and fatigue.
• Niacin contributes to normal psychological function.
• Niacin contributes to the maintenance of normal skin.

Niacin is one of five B vitamins that hold the tiredness claim. Thiamin and biotin do not hold it, though both share the energy-yielding metabolism claim. Our guide to which B vitamins help with tiredness sets out the difference.

Where Immufix fits.

Most people take in plenty of niacin from meat, fish, bread and cereals. Immufix is a daily food supplement for people who want a consistent base under their diet. One scoop (25g) in around 200ml of water, once a day, provides 4.5mg of niacin, which is 28% of the NRV. Niacin contributes to normal energy-yielding metabolism and to the reduction of tiredness and fatigue. Every amount is listed on the science page.

The short version.

• Niacin is vitamin B3, found as nicotinic acid and nicotinamide. The body cannot store it.
• The NHS lists meat, fish, wheat flour and eggs as good sources. Per 100g in CoFID, grilled chicken breast has 15.8mg and canned tuna 10.3mg.
• The body can also make niacin from tryptophan in protein, which is why UK figures use niacin equivalents.
• Adults need about 16.5mg a day (men) or 13.2mg (women). The label NRV is 16mg.
• For supplements, the NHS gives 17mg a day of nicotinic acid, or 500mg of nicotinamide, as unlikely to cause harm.

Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you have a medical condition, are pregnant, breastfeeding or taking medication, speak to your GP or pharmacist before taking any food supplement.