Vitamin B3 (Niacin)

Inositol hexaniacinate; Niacin; Niacinamide; Nicotinamide; Nicotinic acid

Vitamin B3 is one of 8 B vitamins. It is also known as niacin (nicotinic acid) and has 2 other forms, niacinamide (nicotinamide) and inositol hexanicotinate, which have different effects from niacin.

All B vitamins help the body convert food (carbohydrates) into fuel (glucose), which the body uses to produce energy. These B vitamins, often referred to as B-complex vitamins, also help the body use fats and protein. B-complex vitamins are needed for a healthy liver, healthy skin, hair, and eyes, and to help the nervous system function properly.

Niacin also helps the body make various sex and stress-related hormones in the adrenal glands and other parts of the body. Niacin helps improve circulation, and it has been shown to suppress inflammation.

All the B vitamins are water-soluble, meaning that the body does not store them.

You can meet all of your body's needs for B3 through diet. It is rare for anyone in the developed world to have a B3 deficiency. In the U.S., alcoholism is the main cause of vitamin B3 deficiency.

Symptoms of mild B3 deficiency include:

  • Indigestion
  • Fatigue
  • Canker sores
  • Vomiting
  • Poor circulation
  • Depression

Severe deficiency can cause a condition known as pellagra. Pellagra is characterized by cracked, scaly skin, dementia, and diarrhea. It is generally treated with a nutritionally balanced diet and niacin supplements. Niacin deficiency also causes burning in the mouth and a swollen, bright red tongue.

Very high doses of B3, available by prescription, have been studied to prevent or improve symptoms of the following conditions. However, at high doses niacin can be toxic. You should not take doses higher than the Recommended Daily Allowance (RDA) except under your doctor's supervision. Researchers are trying to determine if inositol hexanicotinate has similar benefits without serious side effects. But results are inconclusive.

High cholesterol

Niacin, but not niacinamide, has been used since the 1950s to lower elevated LDL (bad) cholesterol and triglyceride (fat) levels in the blood. However, side effects can be unpleasant and even dangerous. High doses of niacin cause:

  • Flushing of the skin
  • Stomach upset (which usually subsides within a few weeks)
  • Headache
  • Dizziness
  • Blurred vision
  • An increased risk of liver damage

A time-release form of niacin reduces flushing. But long-term use is associated with liver damage. In addition, niacin can interact with other cholesterol-lowering medicines. You should not take niacin at high doses without your doctor's supervision.

Atherosclerosis and heart disease

In one study, men with existing heart disease slowed down the progression of atherosclerosis by taking niacin along with colestipol. They experienced fewer heart attacks and deaths, as well.

In another study, people with heart disease and high cholesterol who took niacin along with simvastatin (Zocor) had a lower risk of having a first heart attack or stroke. Their risk of death was also lower. In another study, men who took niacin alone seemed to reduce the risk of having a second heart attack, although it did not reduce the risk of death.

Diabetes

In type 1 diabetes, the body's immune system mistakenly attacks the cells in the pancreas that make insulin, eventually destroying them. Niacinamide may help protect those cells for a time. More research is needed.

Researchers have also looked at whether high-dose niacinamide might reduce the risk of type 1 diabetes in children at risk for the disease. One study found that it did. But another, larger study found it did not protect against developing type 1 diabetes. More research is needed.

The effect of niacin on type 2 diabetes is more complicated. People with type 2 diabetes often have high levels of fats and cholesterol in the blood. Niacin, often along with other medications, can lower those levels. However, niacin may also raise blood sugar levels, which is particularly dangerous for someone with diabetes. For that reason, if you have diabetes, you should take niacin only under the direction of your doctor, and you should be carefully monitored for high blood sugar.

Osteoarthritis

One preliminary study suggested that niacinamide may improve arthritis symptoms, including increasing joint mobility and reducing the amount of non-steroidal anti-inflammatory drugs (NSAIDs) needed. More research is needed.

Other

Alzheimer disease: Population studies show that people who get higher levels of niacin in their diet have a lower risk of Alzheimer disease. No studies have evaluated niacin supplements, however.

Cataracts: One large population study found that people who got a lot of niacin in their diets had a lower risk of developing cataracts.

Skin conditions: Researchers are studying topical forms of niacin as treatments for rosacea, aging, and prevention of skin cancer, although it is too early to know whether it is effective.

Although there is no evidence that it helps treat any of these conditions, researchers are also studying the use of vitamin B3 in treating:

  • ADHD
  • Migraines
  • Dizziness
  • Depression
  • Motion sickness
  • Alcohol dependence

Dietary Sources

Available Forms

How to Take It

Precautions

Possible Interactions

Supporting Research

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