Niacin (vitamin B3): benefits, sources, dosage, side effects

Niacin is a water-soluble vitamin, meaning that you have to consume it regularly because your body does not store it. Fortunately, niacin is found in many different types of foods (more on that below).

Most Americans get enough niacin in their diets. However, there are some cases where a healthcare provider may recommend niacin supplements. Let’s learn a little more about this B vitamin, how it contributes to helping your body function properly, and what can happen if you become B3 deficient.

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Our body uses niacin, also known as vitamin B3, to convert the food you eat into energy and help the brain function properly, among other things. 

From a biochemical perspective, niacin can refer to a lot of different molecules. For our purposes, it’s enough to understand that our body converts absorbed niacin into its main active form, nicotinamide adenine dinucleotide, or short NAD. Hundreds of enzymes require NAD for important reactions in the body. NAD can be found in the body in two forms: NAD+ or NADH (Mehmel, 2020).

Having enough niacin in the body is important for general good health and many bodily functions. Although more studies are needed to truly understand the impact of NAD metabolism, there is some research to suggest beneficial effects. 

Here’s a look at some of the benefits of niacin and the cases when supplements may help:

Niacin and energy

Niacin helps your body use the food you eat to create energy. This happens through turning the energy from carbohydrates, fats, and proteins into a molecule called ATP (adenosine triphosphate), which powers the cells (NIH, 2021).  

Niacin and the brain

While research has not shown that B vitamins can slow age-related memory loss, studies in mice revealed that NAD reduced the amount of something called “beta-amyloid plaque” in the brain. This plaque is associated with Alzheimer’s Disease. Other studies show that increasing NAD levels can help protect against neurodegenerative conditions—such as Alzheimer’s disease, dementia, and Parkinson’s disease—and may slow down their progression (Johnson, 2018; Gong, 2013).

Research also shows all of the B-vitamins play a role in keeping the brain healthy and that they often work together. That’s why vitamin b3, vitamin b6 and vitamin b12, along with folic acid, are part of a broader B-complex formulation and sold as a single dietary supplement (Kennedy, 2016). 

Niacin, DNA repair, and the skin 

Niacin plays an important role in repairing DNA. Too little of it has been linked to aging, neurodegenerative disease, and cancer (Croteau, 2017). 

DNA repair also includes skin cell repair from sun damage. Niacinamide products—or topical niacin—may help improve some sun damage, such as wrinkles and fine lines. Studies show this form of niacin may also help prevent acne breakouts (Walocko, 2017).  

Niacin and cholesterol

High doses of niacin supplements can reduce overall cholesterol. This includes decreasing the “bad” low-density lipoprotein (LDL) cholesterol and triglycerides while increasing “good” high-density lipoprotein (HDL) cholesterol. Cholesterol does have many benefits for the body, but too much can increase the risk for heart problems. 

Improved blood pressure and heart health

High blood pressure and other so-called metabolic conditions take a toll on the health of blood vessels and arteries. Some research shows that NAD+ supplements can help protect blood vessels, reduce inflammation, and reduce stiffness in the aortic artery (Mehmel, 2020).

However, research does not show that niacin therapy lowers the risk of cardiovascular events like heart attack, or stroke (D’Andrea, 2019; Zeman, 2015). 

Niacin can be found in many foods, including fortified foods. Most Americans get enough niacin from the food they eat. Here are some of the top meat and vegetarian food sources of niacin, and how much of the Daily Value (DV), which is similar to recommended daily allowance (RDA), they contain (NIH, 2021):

• Beef liver (3 ounces [oz]): 14.9 mg; 93% of the DV

• Chicken breast (3 oz): 10 mg; 63% of the DV

• Turkey breast (3 oz): 10 mg; 63% of the DV

• Sockeye salmon (3 oz): 8.6 mg; 54% of the DV

• Brown rice (1 cup): 5.2 mg; 33% of the DV

• Peanuts (1 oz): 4.2 mg; 26% of the DV

• Medium baked potato: 2.3 mg; 14% of the DV

Other foods high in vitamin B3 include sunflower and pumpkin seeds, fortified bread, soy milk, lentils, bananas, raisins, tomatoes, cashews, and yogurt. The amino acid tryptophan can also be converted to NAD. Tryptophan is found in foods like turkey, chicken, fish, seeds, milk, cheese, egg whites, and soy products (NIH, 2021; NLM, 2021).

The following daily recommended allowances (RDAs) show the minimum amount of vitamin B3 needed based on your age group (NIH, 2021): 

• Men (aged 14+): 16 mg NE (one NE is defined as 1 mg of niacin) daily

• Women (aged 14+): 14 mg NE daily

• Women (pregnant): 18 mg daily

• Women (breastfeeding): 17 mg daily

• Infants 0-6 mos: 2mg niacin alone (estimated amount in breast milk)

• Ages 7-12 mos: 4 mg NE

• Ages 1-3: 6 mg NE(based on the amount in breast milk and solid foods)

• Ages 4-8: 8 mg NE

• Ages 9-13: 12 mg NE

• Maximum daily intake for adults of all ages: 35 mg daily

A healthy diet typically covers the RDA of niacin. If your healthcare provider prescribes niacin, there may be instructions like taking it with food or before bed. It’s important to get medical advice from a health professional before taking niacin to make sure the dose is appropriate (NIH, 2021).

You need enough niacin for your body to function well. Yet, too much can be toxic. Here’s a look at how to identify both a niacin deficiency and an overdose:

Niacin (vitamin B3) deficiency

Before the fortification of food, niacin deficiency was fairly common in the United States. Severe niacin deficiency causes a disease called pellagra, which causes skin problems, diarrhea, dementia, and can lead to death (Redzic, 2021). Today in the U.S., cases of pellagra are rare. However, niacin deficiency can be a problem, especially for those who have a diet low in vitamin B3, tryptophan, or vitamins B1, B2, B6, or iron, which can reduce the amount of tryptophan that converts to NAD (Gasperi, 2019).  

Those with vitamin B3 deficiencies often suffer from poor nutrition, anorexia, or alcoholism, which can make it harder to absorb vitamin B3. Other conditions such as inflammatory bowel disease and conditions that make it hard to absorb nutrients, such as Crohn’s disease, can also lead to a niacin deficiency. Having cancer or going through chemotherapy also increases the risk of deficiency (Gasperi, 2019).

If you have a deficiency, your healthcare provider can advise you on the best way to safely boost niacin levels based on results. Oral nicotinamide is usually used to treat a niacin deficiency (NIH, 2021; Redzic, 2021).

Niacin (vitamin B3) side effects

Niacin side effects can occur if you take supplements, especially at a high dose. It's not possible to overdose on niacin simply by eating too many niacin-rich foods. The side effects of high-dose niacin include low blood pressure, falls, fatigue, blood sugar problems, insulin resistance, nausea, heartburn, abdominal pain, and blurred vision (NIH, 2021). 

Some niacin supplements have been formulated to be “sustained-release” tablets—meaning they dissolve slower in your body—to reduce the amount of flushing typically associated with niacin (NIH, 2021). 

Sometimes niacin side effects are worse or lead to health problems if taken with certain drugs or supplements. Consuming alcohol and taking high-dose niacin can worsen side effects like skin flushing and increase the risk of liver damage. Those with liver disease should be cautious of taking too much vitamin B3 (NIH, 2021).

It’s best to talk with a healthcare provider before taking niacin and discuss any medications that may cause an adverse reaction. As with all vitamins, it’s best to balance vitamin B3 and ensure you have enough, but not too much (Djadjo, 2021).

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Current version

December 20, 2021

Written by

Kristin DeJohn

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.