We continue with our nutrient spotlight journey through the B vitamins by taking a look at vitamin B3. More commonly known as niacin, as well as niacinamide, nicotinamide and nicotinic acid. Niacin is one of the 'big hitters' in metabolism. After all, we need vitamin B3 for a large number of biochemical reactions in our bodies. Further still, we also need relatively large amounts for optimum health.
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What is vitamin B3 | niacin?
Pure niacin is a white needle-like crystalline substance which easily dissolves in water. However, unlike most other vitamins, niacin remains stable at high temperatures. Therefore, cooking doesn't break it down in the same way as other vitamins. For example, up to 120 degrees C - even in the presence of oxygen.
To clarify, niacin is actually the common name given to two compounds; nicotinic acid and niacinamide. Our body can easily convert both of these to the biologically active form. However, despite the similarity in name, neither of these compounds is related to the drug nicotine.
Why do I need vitamin B3 | niacin?
Niacin is absolutely critical for energy production. In particular, it's required for 2 coenzymes known as NAD and NADP.
These enzymes are at the heart of the energy-releasing pathways in carbohydrate and fat metabolism. Specifically, these enzymes help to shuttle hydrogen and electrons in redox reactions. You may remember back to your high school chemistry days - redox reactions are a combination of reduction and oxidation.
Our body releases and harnesses chemical energy from the foods we eat. Overall, niacin functions in more than 50 metabolic reactions.
Additionally, we also use vitamin B3 to process amino acids. Likewise, we use niacin to synthesise body fats as well as metabolise several drugs and toxins. Finally, we even use vitamin B3 to form new red blood cells.
How much vitamin B3 or niacin do I need in my diet?
Guidelines vary between different countries.
In the UK, the Reference Nutrient Intake (RNI) for niacin is 17mg per day for 19-50-year-old men, and 16mg per day for those who are older. By comparison, the figures for women are 13mg and 12mg per day for the same respective age groups. Additionally, lactating women are advised to consume an extra 2mg per day on top of their normal requirement,
Meanwhile, in the United States, the Recommended Dietary Allowance (RDA) for niacin is 16mg for men and 14mg for women. Again, lactating women are advised to consume higher amounts, this time by an additional 3mg per day. Whereas pregnant women are advised to meet an RDA of 18mg of vitamin B3 per day.
Likewise, in Australia, the Recommended Dietary Intake (RDI) for niacin is similar to the US at 16mg and 14mg for men and women respectively. Figures for pregnant and lactating women are also similar to the United States RDAs.
Dietary Guidelines for vitamin B3 | niacin intake in the UK, USA and Australia
COUNTRY | MEN 19-50 | WOMEN 19-50 |
|---|---|---|
United Kingdom Reference Nutrient Intake (RNI) | 17mg | 13mg |
United States Recommended Dietary Allowance (RDA) | 16mg | 14mg |
Australia Recommended Dietary Intake (RDI) | 16mg | 14mg |
In either case, it's important to remember that these are generally the minimum recommendations. In general, due to their water solubility, B vitamins tend to be fairly non-toxic. Since niacin is essential for energy production in food metabolism pathways, we often require more. For example, in athletes and other active people with high-calorie intakes upwards of 3,000 kcal per day, more niacin may be necessary.
Where can I find vitamin B3 in my diet? Which foods are rich sources of niacin?
The best sources of vitamin Br (niacin) are protein foods such as liver, kidney, beef, chicken, nuts, milk and eggs. Additionally, whole grain unrefined bread and cereals are quite good sources, as are some vegetables. However, most fruits are a poor source of niacin. Furthermore, processed or refined foods, especially sweets and sugary foods are very poor sources.
In general, white bread and flour products are reasonable sources, but only because white flour is fortified.
Although we label niacin a vitamin, our body can synthesise B3 from the amino acid tryptophan. In particular, this source provides on average around half of our needs. In fact, tryptophan comprises around 1% of dietary protein and each 60mgs of tryptophan is equivalent to 1mg of niacin.
Therefore, 100 grams of dietary protein can supply around 16mg of niacin. This explains why some tryptophan-rich proteins such as milk and eggs are especially good sources of niacin.
What are the symptoms of niacin deficiency? What happens if I don't get enough vitamin B3?
A severe niacin deficiency leads to pellagra, a serious condition characterised by 3 'D's:
The 4th 'D' is death.
However, less severe deficiencies may cause symptoms such as poor memory, headaches, fatigue and irritability. Also, nausea and loss of appetite, tender gums, rough or inflamed skin, anxiety or tension and depression may result.
Who should take the most care to regulate their vitamin B3 | niacin intake?
Undoubtedly, people on very low-calorie diets are most at risk of a low niacin intake. Additionally, if you are on a low-protein diet, you may have to take care to ensure you get enough vitamin B3.
Furthermore, diets high in junk food and highly processed or sugary, refined foods are at risk of not meeting their recommended niacin intake.
Finally, it's worth noting that heavy alcohol consumption depletes niacin levels too.
Am I getting enough vitamin B3 | niacin in my diet?
The best sources of niacin are protein foods such as kidney, beef, liver, chicken, fish, nuts, milk and eggs. On the other hand, fruits and sugary, refined or processed foods are poor sources.
Niacin Content of Various Foods
Food | Niacin Content (milligrams) per 100 grams of edible portion |
|---|---|
Baked Beans | 1.48 |
Beef Steak | 10.06 |
Carrots (raw) | 0.16 |
Cheddar Cheese | 5.47 |
Grilled Barramundi | 9.34 |
Lettuce (iceberg) | 0.11 |
Milk | 0.81 |
Peanuts (roasted) | 22.85 |
Peas (frozen) | 2.02 |
Pork Chop | 10.52 |
Potatoes (baked with skin) | 2.44 |
Roast Chicken Breast | 17.70 |
Strawberries | 0.25 |
Tuna (canned, drained) | 18.18 |
Figures supplied by the Australian Food Composition Database and AusFoods 2019
This article is part of a series examining different nutrients and our requirements for them. Read other articles in my nutrient spotlight series.
Can I get too much vitamin B3 | niacin?
For the most part, niacin in the form of nicotinamide is relatively non-toxic.
Even in large doses, supplementing up to 900mg per day for long periods of time is generally safe. That's according to Australia's national guidelines, as well as advice from the European Commission (2002).
However, niacin supplemented as nicotinic acid can produce vasodilation and flushing of the skin. Especially when doses exceed 30-40mg per day, and this can be uncomfortable.
Those with a history of liver problems, diabetes, gout, ulcers and migraine headaches should also avoid high doses of niacin in the form of nicotinic acid.
