Vitamin B-3 (Niacin)

Niacin is a form of vitamin B3. It is found in foods such as yeast, meat, fish, milk, eggs, green vegetables, and cereal grains. Niacin is also produced in the body from tryptophan, which is found in protein-containing food. When taken as a supplement, niacin is often found in combination with other B vitamins.

Do not confuse niacin with niacinamide, inositol nicotinate, IP-6, or tryptophan. See the separate listings for these topics.

Niacin is taken by mouth for high cholesterol and other fats. It is also used for low levels of a specific type of cholesterol, HDL. It is also used along with other treatments for circulation problems, migraine headache, Meniere's syndrome and other causes of dizziness, and to reduce the diarrhea associated with cholera. Niacin is also taken by mouth to for preventing positive urine drug screens in people who take illegal drugs.

Niacin is taken by mouth for preventing vitamin B3 deficiency and related conditions such as pellagra. It is also taken by mouth for schizophrenia, hallucinations due to drugs, Alzheimer's disease and age-related loss of thinking skills, chronic brain syndrome, muscle spasms, depression, motion sickness, alcohol dependence, blood vessel swelling linked with skin lesions, and fluid collection (edema).

Some people take niacin by mouth for acne, leprosy, attention deficit-hyperactivity disorder (ADHD), preventing premenstrual headache, improving digestion, protecting against toxins and pollutants, reducing the effects of aging, arthritis, lowering blood pressure, improving circulation, promoting relaxation, improving orgasms, and preventing cataracts. It is also used to improve exercise performance.

How does it work?

Niacin is absorbed by the body when dissolved in water and taken by mouth. It is converted to niacinamide if taken in amounts greater than what is needed by the body.

Niacin is required for the proper function of fats and sugars in the body and to maintain healthy cells. At high doses, niacin might help people with heart disease because of its beneficial effects on clotting. It may also improve levels of a certain type of fat called triglycerides in the blood.

Niacin deficiency can cause a condition called pellagra, which causes skin irritation, diarrhea, and dementia. Pellagra was common in the early twentieth century, but is less common now, since some foods containing flour are now fortified with niacin. Pellagra has been virtually eliminated in western culture.

People with poor diet, alcoholism, and some types of slow-growing tumors called carcinoid tumors might be at risk for niacin deficiency.

Abnormal levels of blood fats.
Treatment and prevention of niacin deficiency, and certain conditions related to niacin deficiency such as pellagra.
Hardening of the arteries (atherosclerosis).
Diarrhea from an infection called cholera.
Abnormal levels of blood fats in people with HIV/AIDS.
Metabolic syndrome.

Adults

By Mouth:

For high cholesterol: The effects of niacin are dose-dependent. Doses of niacin have been as low as 50 mg and as high as 12 grams each day have been used. However, the most common doses are between 1-3 grams daily. Biggest increases in HDL and decreases in triglycerides occur at 1200-1500 mg/day. Niacin's greatest effects on LDL occur at 2000-3000 mg/day. Niacin may be is often used with other medications for improving cholesterol levels.

For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 300-1000 mg daily in divided doses.

For treating hardening of the arteries: Doses of niacin have been as high as 12 grams daily. However, dose of about 1000-4200 mg1-4 grams of niacin daily, alone or along with statins or bile acid sequestranscholesterol-lowering medicine, has been most commonly used for up to 6.2 years.

For reducing fluid loss caused by cholera toxin: 2 grams daily has been used.

For abnormal blood fat levels due to treatment for HIV/AIDS: Up to 2 grams daily has been used.

For metabolic syndrome: 2 grams of niacin has been taken daily for 16 weeks. In some cases it is taken Niacin 2 grams daily, alone or at this dosage along with 4 grams of prescription omega-3 ethyl esters (Lovaza, GlaxoSmithKline Pharmaceuticals)

By IV:

For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 60 mg of niacin has been used.

As a Shot:

For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 60 mg of niacin has been used.

Children
By Mouth:

For preventing and treating vitamin B3 deficiency and related conditions such as pellagra: 100-300 mg per day of niacin, given in divided doses.

Niacin is SAFE for most people when taken by mouth. A common minor side effect of niacin is a flushing reaction. This might cause burning, tingling, itching, and redness of the face, arms, and chest, as well as headaches. Starting with small doses of niacin and taking 325 mg of aspirin before each dose of niacin will help reduce the flushing reaction. Usually, this reaction goes away as the body gets used to the medication. Alcohol can make the flushing reaction worse. Avoid large amounts of alcohol while taking niacin.

Other minor side effects of niacin are stomach upset, intestinal gas, dizziness, pain in the mouth, and other problems.

When doses of over 3 grams per day of niacin are taken, more serious side effects can happen. These include liver problems, gout, ulcers of the digestive tract, loss of vision, high blood sugar, irregular heartbeat, and other serious problems.

Some concern has been raised about stroke risk in people taking niacin. In one large study, people who took high doses of niacin had a two-fold greater risk of stroke compared to those not taking niacin. However, it is unlikely that this outcome was due to niacin. Most experts believe that it is too soon to draw any conclusions about niacin and strokes.

Pregnancy and breast-feeding: Niacin is LIKELY SAFE for pregnant and breast-feeding women when taken in the recommended amounts. The recommended amount of niacin for pregnant or breast-feeding women is 30 mg per day for women under 18 years of age, and 35 mg for women over 18.

Allergies: Niacin might worsen allergies by causing histamine, the chemical responsible for allergic symptoms, to be released.

Heart disease/unstable angina: Large amounts of niacin can increase the risk of irregular heartbeat. Use with caution.

Crohn's disease: People with Crohn's disease might have low niacin levels and require supplementation during flare-ups.

Diabetes: Niacin might increase blood sugar. People with diabetes who take niacin should check their blood sugar carefully.

Gallbladder disease: Niacin might make gallbladder disease worse.

Gout: Large amounts of niacin might bring on gout.

Kidney disease: Niacin might accumulate in people with kidney disease. This might cause harm.

Liver disease: Niacin might increase liver damage. Don't use large amounts if you have liver disease.

Stomach or intestinal ulcers: Niacin might make ulcers worse. Don't use large amounts if you have ulcers.

Very low blood pressure: Niacin might lower blood pressure and worsen this condition.

Surgery: Niacin might interfere with blood sugar control during and after surgery. Stop taking niacin at least 2 weeks before a scheduled surgery.

Fatty deposits around tendons (tendon xanthomas): Niacin might increase the risk of infections in xanthomas.

Thyroid disorders: Thyroxine is a hormone produced by the thyroid gland. Niacin might lower blood levels of thyroxine. This might worsen symptoms of certain thyroid disorders.