Vitamin B3: Benefits, Sources and Side Effects

Vitamin B3, also called niacin, is one of the B complex vitamins. It is vital for cell metabolism, DNA repair, maintaining good skin, and gastrointestinal and brain health. Severe vitamin B3 deficiency may cause diseases such as pellagra. In this article, you’ll learn about vitamin B3: sources, functions, deficiency, health benefits, and side effects.

Key takeaways:

What is vitamin B3?

Vitamin B3, also known as niacin, is a water-soluble vitamin. Vitamin B3 exists in different forms, including:

  • Nicotinamide
  • Nicotinic acid
  • Nicotinamide riboside
  • Nicotinamide adenine dinucleotide (NAD)
  • Nicotinamide adenine dinucleotide phosphate (NADP)

We get vitamin B3 from animal and plant foods in these different forms of niacin, mostly nicotinamide and nicotinic acid.

Dietary niacin is converted to NAD and NADP, metabolically active forms of vitamin B3. Nicotinamide adenine dinucleotide is a coenzyme required for more than 400 enzymes, which catalyze vital physiological mechanisms. Additionally, NAD is converted to NADP, another coenzyme.

Our bodies can also synthesize some amount of vitamin B3 from tryptophan, an amino acid. In the liver, tryptophan is converted to vitamin B3 and transferred to other tissues. High-quality protein consumption can increase the tryptophan-nicotinamide conversion.

Vitamin B3 functions in the body

One of the B complex vitamins, vitamin B3, has important functions in the body. Examples include the following:

  • Niacin is vital for metabolism and energy production. NAD and NADP (coenzyme forms of vitamin B3) are required for energy and nutrient metabolism.
  • Vitamin B3 may show anti-dyslipidemic effects. Niacin has been given along with statin medications to reduce total cholesterol, triglycerides, and LDL (bad cholesterol) and increase HDL (good cholesterol).
  • Vitamin B3 keeps the skin healthy. A severe vitamin B3 deficiency can cause skin sensitivity to sunlight (UV radiation). Although evidence is still unclear, topical or oral use of niacin has been thought to increase skin immunity and reduce the risk of skin cancer.
  • Vitamin B3 keeps the gastrointestinal system healthy. Vitamin B3 deficiency can cause gastrointestinal problems such as vomiting, diarrhea, and constipation.
  • Vitamin B3 has a role in neuroprotection. Neurons (brain cells) are sensitive to decreases in NAD levels. Therefore, vitamin B3 deficiency can cause neurological symptoms such as headaches, fatigue, memory problems, and depression.
  • Vitamin B3 is necessary for DNA repair. Nicotinamide (a form of vitamin B3) is the primary precursor of NAD, which is an essential coenzyme for the DNA repair enzyme poly-ADP-ribose polymerase-1 (PARP-1).
  • Vitamin B3 plays a role in cell growth and aging. Research has shown that reduced NAD concentration in cells can negatively impact cell division and growth, leading to cell death and aging.

Causes of vitamin B3 deficiency

Niacin is found in commonly consumed foods, so deficiency is rare: 1% of adults. However, severe niacin deficiency can cause pellagra, a nutritional disorder causing problems in the skin, gastrointestinal, and nervous systems.

Some medications, such as isoniazid, pyrazinamide, and antidiabetes medications, may interact with niacin. If you’re taking such drugs regularly, you can discuss your niacin status with your healthcare providers.

Excessive alcohol consumers, people with Hartnup disease, and some gastrointestinal cancers can also cause severe vitamin B3 deficiency.

Vitamin B3 sources

Niacin is found in both animal and plant foods, including red meat, poultry, fish and shellfish, brown rice, peanuts, fortified breakfast cereals, white rice, and legumes.

FoodsNiacin (mg) / per servingPercent of the daily value
Beef liver15 mg / 3 ounces93%
Poultry 10 mg / 3 ounces63%
Salmon 9 mg / 3 ounces54%
Tuna9 mg / 3 ounces54%
Ground beef, 80% lean6 mg / 3 ounces36%
Brown rice5 mg / 1 cup33%
White rice2 mg / 1 cup14%
Peanuts4 mg / 1 ounce26%
Lentils, boiled1 mg / 0.5 cup6%

Vitamin B3 dietary recommendations

According to the UK National Health Service, adults need 15 mg of niacin on average. Women need 14 mg; men need 16 mg of niacin daily.

Additionally, niacin intake must increase to 17 mg and 18 mg during lactation and pregnancy, respectively.

Side effects and toxicity of niacin

It’s unlikely that someone will experience side effects from consuming niacin in foods. However, dietary supplements of niacin and nicotinamide may cause side effects and toxicity if taken in excess.

The maximum daily intake to prevent adverse health effects for niacin is 35 mg daily. As a result, supplementation of 30 to 50 mg niacin was reported to cause side effects such as:

  • Flushing, burning, and itching feeling on the skin
  • Headache
  • Rash
  • Dizziness
  • Lowered blood pressure

Doses of 1000 to 3000 mg/day of niacin can cause serious side effects, including hypotension, fatigue, nausea, heartburn, abdominal pain, changes in vision, impaired glucose tolerance, and insulin sensitivity. Therefore, high doses are generally given for treatment purposes.

You don’t need to be concerned about vitamin B3 deficiency if you consume a healthy and balanced diet. To optimize the benefits of vitamin B3, incorporate foods that are good niacin sources.

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