Vitamin B3, also known as niacin, is one of the B-complex vitamins. It’s a water-soluble vitamin naturally found in many vitamin B3 foods and dietary supplements.
Niacin is a generic term for the various forms of vitamin B3. In other words, vitamin B3 derivatives such as nicotinamide riboside, nicotinamide (niacinamide or pyridine-3-carboxamide), and nicotinic acid (pyridine-3-carboxylic acid) are all generically referred to as niacin.
The most well-known niacin-rich foods, as it’ll be described in detail in the following paragraphs, include liver, chicken, turkey, ground beef, fish, and avocado. However, you’ll also learn that tryptophan-rich food sources may also be regarded as sources of niacin. This is because our bodies can convert tryptophan to NAD (nicotinamide adenine dinucleotide), a form of niacin.
Read on to find out about the major sources of vitamin B3, how niacin is absorbed and excreted, and details about deficiency and toxicity.
Vitamin B3 Absorption and Excretion
Most B3-rich foods contain niacin in the nicotinic acid and nicotinamide form. On the other hand, a small number of food items provide niacin in NAD and NADP form that need to be converted to nicotinamide in the gut before absorption. Additionally, some foods (such as turkey) contain tryptophan—an amino acid that the body converts to NAD and then to nicotinamide before they can go through the absorption process.
As previously mentioned, the absorption starts with breaking down niacin foods in the stomach, where niacin is converted to nicotinamide. Afterward, this compound is transferred to the small intestine, where it’s absorbed.
Since the small intestine is well-suited for absorbing niacin, it’s capable of completely absorbing even high doses of B3 vitamin (3–4 g) at once. Upon absorption, physiological amounts of niacin are converted back to nicotinamide adenine dinucleotide (NAD)—niacin’s primary metabolically active form.
This coenzyme is crucial for various body processes. Namely, over 400 enzymes need NAD to catalyze countless metabolic reactions—more than any other coenzyme derived from other vitamins.
NAD can go through another conversion to become NADPH (nicotinamide adenine dinucleotide phosphate), another active form of niacin present in all body tissues save for the skeletal muscle.
NADPH and NAD – available in vitamin b3 supplement products and food – are indispensable in metabolic oxidation and reduction processes. For example, NAD has a significant role in catabolic reactions in the body (breaking down large molecules into smaller molecules).
In other words, NAD is involved in transferring energy from proteins, carbohydrates, and fats to ATP—the primary source of cellular energy. It’s also involved in maintaining cellular communication, genome integrity, etc.
On the other hand, NADP’s primary role relates to anabolic reactions—cholesterol and fatty acid production and antioxidant function.
All in all, metabolic processes, as well as anabolic and catabolic reactions, are necessary for optimal body function, which is why we should make sure to maintain adequate B3 vitamin intake.
Sometimes, not all vitamin B3 from niacin food sources or supplements gets used up by the body upon absorption. This is especially true when you consume excessive amounts of this vitamin.
In that case, erythrocytes (red blood cells) take up the excess niacin and create a circulating reserve pool. The remainder gets methylated to N1-methyl-2-pyridone-5-carboxamide, N1-methyl-nicotinamide, and other pyridone products by the liver hepatocytes. These methylated products are then excreted through urine.
The best natural source of vitamin B3 is food. There are plenty of foods high in niacin. Animal food sources (poultry, fish, and meat) offer high levels of niacin (about 5–10 mg), primarily in the highly bioavailable NAD and NADPH forms.
Plant sources (legumes, nuts, and grains) offer lower levels of niacin (about 2–5mg), primarily in nicotinic acid form. The bioavailability of plant-based foods with niacin is also lower than in animal-based sources.
This is because most of the niacin in plant sources is covalently bound to carbohydrate molecules (polysaccharides and glycopeptides), which reduces bioavailability by almost 70%.
Additionally, foods with tryptophan are also good sources of vitamin B3. Tryptophan is an amino acid that the liver can convert to NAD—a form of niacin.
Research shows that the conversion rate of tryptophan to NAD is at 1:60 (1 mg niacin from 60 mg tryptophan). However, this rate isn’t constant because the ability of the liver hepatocytes to convert tryptophan to niacin varies among individuals.
Finally, apart from natural B3 foods sources, you can get niacin from processed foods fortified with niacin. Now, let’s take a close look at some of the top food sources of niacin.
Animal Sources of Niacin
Animal-based sources of vitamin B3 provide more niacin than plant sources, mainly due to their bioavailability. We’ll now look at top animal sources and how each contributes to the recommended dietary allowance of niacin.
If you’re looking to feed your cells with niacin, the animal liver is all you need, provided you aren’t vegetarian. Namely, liver (beef or chicken) is undoubtedly the best source of niacin.
Namely, a 3 oz serving of cooked beef liver contains 14.7 mg of niacin. This is equivalent to 91% RDA for men and over 100% RDA for women.
On the other hand, 3 oz of chicken liver provides slightly lower amounts of vitamin B3—about 73% RDA for men and 83% RDA for women.
Pork is also one of the excellent vitamin B3 foods. Pork tenderloin and lean pork chops are the best cuts of meat for increasing your niacin levels. Other parts, such as pork shoulder, offer lower levels of niacin.
For example, a 3 oz serving of roasted pork tenderloin provides about 6.3 mg of niacin, which is about 45% of the RDA for women and 39% of the RDA for men.
On the other hand, roasted pork shoulder provides only 24% RDA for women and 20% RDA for men.
Additionally, besides being one of the best niacin foods, pork plays a role in various metabolic functions, as it’s also a rich source of vitamin B1.
Chicken breast also ranks high among vitamin b3 foods. A 3 oz serving of cooked chicken breast with no bones or skin contains 11.4 mg of niacin, which amounts to 71% RDA for males and 81% RDA for females.
Apart from being a good source of niacin, chicken breast is also an excellent source of protein. Namely, cooked chicken breast can provide up to 8.7 g of protein per ounce. Thus, chicken breast is well suited for individuals on a high protein, low-calorie diet, seeking an increase in vitamin B3 levels and weight loss.
Turkey can also be regarded as one of the best dietary sources of niacin despite containing low amounts of vitamin B3. This is because this large bird is an excellent source of tryptophan, which can be converted to niacin by the liver hepatocytes.
A 3 oz serving of boiled turkey breast provides up to 6.3 mg of niacin coming from converted tryptophan. This amount accounts for about 46% RDA for males and 52% RDA for females.
Tryptophan can also be converted to 5-hydroxytryptamine (5HT) and then to serotonin, which plays a vital role in mood stabilization.
Additionally, tryptophan can also be converted to melatonin in the pineal gland, a substance that controls the sleep-wake cycle and plays a significant role in setting and maintaining the circadian rhythm.
If you’re a pescatarian or simply a fan of seafood, tuna could be your go-to food with niacin. A single can of tuna weighing roughly 5.8 oz 168 g provides up to 21.9 mg of niacin, which is above 100% RDA for both women and men.
Additionally, tuna contains other useful nutrients such as proteins, pyridoxine, cyanocobalamin, selenium, and polyunsaturated fatty acids.
However, consuming tuna is often related to mercury toxicity since this chemical element tends to accumulate in this fish’s flesh.
Another food rich in niacin in the fish category is salmon. A 3 oz serving of cooked wild Atlantic salmon provides over 53% of the recommended dietary allowance for males and 61% of the recommended dietary allowance for females.
Research shows that the farmed variety is among the slightly less rich salmon niacin sources containing 49% RDA for women and 42% for men.
Additionally, salmon is an excellent source of omega-3 fatty acids, a critical factor in preventing inflammatory, cardiovascular, and autoimmune conditions.
Anchovies offer modest levels of niacin, but they’re incredibly affordable. In other words, they’re one of the best inexpensive foods with B3 for attaining your niacin RDA levels.
One anchovy offers about 5% of the RDA for both men and women. Though this amount might sound relatively small, you should bear in mind that snacking on only 10 anchovies a day can provide you with 50% vitamin B3 RDA.
Additionally, anchovies are a good source of selenium, which may help reduce the risk of some forms of cancer (prostate, stomach, breast, etc.), according to research.
Plant Sources of Niacin
If you’re a vegan looking to broaden your knowledge of vitamin B3-rich foods, this section could interest you. The following paragraphs will discuss excellent plant sources of niacin which, although not as bioavailable as the animal sources, are good enough to keep niacin deficiency at bay.
Peanuts are one of the go-to vitamin B3 foods for vegetarian diet followers looking to up their niacin levels. This is because you can get up to 4.3 mg of niacin from two tablespoons of peanut butter, or about 25% RDA for men and 30% RDA for women.
Besides offering decent amounts of B3 vitamin, peanuts are also good protein sources of protein, tocopherol, pyridoxine, phosphorus, magnesium, manganese, and monounsaturated fatty acids.
Avocados are one of the few vitamin B3 fruits. One avocado can provide up to 3.5 mg of niacin, which translates to 21% RDA for men and 25% RDA for women.
Additionally, avocados are good sources of monounsaturated fatty acids, fiber, vitamins, minerals, and potassium. What’s more, it contains twice the amount of potassium in comparison to bananas.
If you don’t eat meat, you should get yourself some mushrooms since they’re among the excellent niacin-rich foods for vegetarian diet followers. A single cup of these nutritions and beneficial fungi contains about 2.5 mg of niacin. This is about 15% RDA for males and 18% RDA for females.
Studies show that mushrooms are also a good source of vitamin D.
It’s common knowledge that this popular starchy vegetable is an excellent source of carbs. But did you know that potatoes are also good niacin food sources?
Only one baked potato provides about 4.2 mg of niacin, which is 25% and 30% RDA for males and females, respectively.
Furthermore, Russet potatoes are particularly rich in vitamin B3, offering 2 mg of niacin per 100g (3.5 oz).
Recommended Dietary Intake
FNB (The Food and Nutrition Board) is responsible for providing the recommended dietary intake of niacin and other nutrients.
The recommended dietary allowance for niacin in food is measured in mg NE (niacin equivalents). One NE is defined as 1 mg of niacin or 60 mg of tryptophan that can be converted to niacin by the body.
The RDAs for different age and gender groups are given in the table below:
|0–6 months||2 mg||2 mg|
|7–12 months||4 mg NE||4 mg NE|
|1–3 years||6 mg NE||6 mg NE|
|4–8 years||8 mg NE||8 mg NE|
|9–13 years||12 mg NE||12 mg NE|
|14–18 years||16 mg NE||14 mg NE||18 mg NE||17 mg NE|
|19+ years||16 mg NE||14 mg NE||18 mg NE||17 mg NE|
Determining Niacin Status
Measuring niacin levels in the body is essential for detecting niacin deficiency.
Surprisingly, blood levels of niacin aren’t reliable enough to give a good indication of niacin levels. On the other hand, measuring the urine excretion rates of 1-methyl-2-pyridone-5-carboxamide and N1-methyl-nicotinamide provides the most accurate representation of the amount of B3 vitamin in the body.
Excreting over 17.5 mmol of these methylated compounds per day is regarded as normal. The excretory rate of 5.8–17.5 mmol per day indicates low niacin levels, and anything below 5.8 mmol is viewed as a sign of B3 deficiency.
It’s important to note that the lack of vitamin B3 is usually evident from excretion rates well before any clinical signs of deficiency start to manifest.
Vitamin B3 Deficiency
When niacin levels abnormally reduce, niacin deficiency ensues. Just like other deficiencies, vitamin B3 deficiency is less common in developed countries than in developing ones. This is because the latter are at greater risk of inadequate intake of niacin-rich foods due to poverty or restricted access to quality food.
There are three classic clinical vitamin B3 deficiency symptoms. They are referred to as the three D’s and comprise dermatitis (flat and pigmented localized rash), diarrhea, and dementia. Severe deficiency leads to a skin condition called pellagra.
Forms of Niacin Deficiency
Niacin deficiency comes in two forms—primary and secondary. Primary niacin deficiency is also called dietary niacin deficiency since it results from an inadequate intake of vitamin B3 and tryptophan from food. It can also be associated with other vitamin and mineral deficiencies. As previously mentioned, this form of deficiency usually occurs in underdeveloped areas of the world with limited access to foods rich in niacin.
Furthermore, this deficiency is prevalent in areas where corn is the main building block of the diet. This is because the protein in corn provides a meager amount of tryptophan. Additionally, niacin in maize is bound to other molecules and can’t be released until treated with an alkali.
Secondary niacin deficiency usually occurs due to gastroenteritis, cirrhosis, chronic alcoholism, and other conditions that decrease niacin absorption.
For example, tryptophan doesn’t convert to niacin in carcinoid syndrome patients. Instead, the body oxidizes it to serotonin, leaving the body without a crucial ingredient for forming niacin.
On the other hand, Hartnup disease leads to the lack of niacin by preventing its absorption into the small intestine. Therefore, instead of getting used by the body, the majority of vitamin B3 is excreted through urine.
Niacin Deficiency Symptoms
The main clinical manifestations of vitamin B3 deficiency are evident in the integumentary system (skin and mucous membranes), central nervous system, and gastrointestinal system.
Symptoms of severe deficiency commonly result in pellagra, a condition causing characteristic rash, red and flaky skin, or brown patches on areas of the body exposed to the sun. It usually manifests as glove-shape discoloration on hands (pellagrous glove), boot-shaped marks on feet (pellagrous boot), Casal collar, and butterfly-shaped patches on the face.
Glossitis and stomatitis are some of the symptoms manifesting on the mucous membrane. In other words, severe niacin deficiency may cause tongue and mouth swelling and redness.
Furthermore, constipation, vomiting, diarrhea, impaired consciousness, mania, dementia, memory loss, hallucinations, and depression also affect niacin deficient individuals.
There’s no evidence that consuming large amounts of B3-rich foods can result in toxicity or produce serious adverse effects. Nevertheless, the excessive intake of niacin supplements can lead to adverse effects.
Taking 30–50 mg of nicotinic acid commonly produces mild, unpleasant symptoms within the first half an hour from overdose:
- Arms, face, and chest flushing
- Itching, tingling, or burning sensation
- Low blood pressure
Taking 1,000–3,000 mg a day may lead to more severe lack of niacin side effects such as:
- Insulin resistance
- Reduced glucose tolerance
- Stomach discomfort
- Macular edema
- Blurred vision
The symptoms mentioned above are usually short-lived and can be reduced or eliminated by lowering the dose or increasing the body’s tolerance to this vitamin. However, prolonged intake of excessively high doses can be gravely damaging to the liver. Namely, it can cause an increase in liver enzymes and overall liver dysfunction, leading to hepatitis, nausea, fatigue, anorexia, and even liver failure.
Avoiding Niacin Toxicity
To decrease the risk of adverse effects caused by vitamin B3 supplement products, the American College of Cardiology and the American Heart Association recommend measuring each patient’s transaminase, fasting blood glucose (glycated hemoglobin), and uric acid levels before prescribing niacin supplements.
Furthermore, they recommend refraining from vitamin B3 tablets and other supplemental forms if your hepatic transaminase levels reach twofold or threefold values than normal. This also applies to developing persistent hyperglycemia, abdominal pain with no clear etiological pointer, show unexplained weight loss, have new-onset atrial fibrillation, or unusual skin changes such as rashes or flushing.
Though vitamin b3 foods are generally widely available, individuals in the developing parts of the world still record high cases of niacin deficiency. This has been a cause of concern for top health institutions such as the WHO. These bodies continue to advise individuals to, as much as possible, eat a balanced diet.
Hopefully, this article gave you all the necessary information about vitamin B3 function, the most important sources, benefits, and how to prevent potential deficiency.
Are vitamin B3 and niacin the same thing?
The short answer is yes. Niacin is an alternative vitamin B3 name and can be used as a generic term for various vitamin B3 forms. Therefore, nicotinic acid (pyridine-3-carboxylic acid), nicotinamide (niacinamide or pyridine-3-carboxamide), and other less common derivatives nicotinamide riboside may all be referred to as niacin.
What is the B3 vitamin good for?
Vitamin B3 helps regulate fat and carbohydrate metabolism in the body. Additionally, it helps reduce LDL cholesterol (bad cholesterol) levels that contribute to coronary artery disease. By lowering LDL levels, vitamin B3 helps protect the heart against cardiovascular diseases.
Additionally, vitamin B3 can function as a powerful skin-protecting tool. NAD aids DNA repair and ensures that your skin stays healthy and clear. Recent studies indicate that this vitamin can offer UV damage protection and even reduce the risk of particular types of skin cancer. Furthermore, this vitamin’s acne-reducing and anti-inflammatory properties are the biggest reason why people often use vitamin B3 for the skin.
Finally, vitamin B3 also enhances brain and gastrointestinal functions.
What is the best source of niacin?
Highly bioavailable animal-based food sources such as beef liver are the best sources of niacin. Beef liver contains 14.7 mg of niacin and over 100% RDA per 3 oz serving.
How can I get vitamin B3 naturally?
The best natural source of vitamin B3 is food. Animal-based sources of niacin include liver, salmon, and tuna. Plant-based sources of niacin include potatoes and avocado.
What fruits and vegetables are high in niacin?
A good example of fruit rich in niacin is avocado. Banana, watermelon, cherries, and oranges are all good vitamin B3 fruits, bearing in mind that bananas are higher in niacin than the rest. Lettuce and pumpkin are great vegetable sources of niacin.
What are the symptoms of vitamin B3 deficiency?
There are three main symptoms of niacin deficiency. They’re referred to as the three D’s and include dermatitis, diarrhea, and dementia.
To prevent deficiency, make sure you include enough vitamin B3 foods into your diet.