Vitamin B3 Overview
Vitamin B 3 is required for the proper function of more than 50 enzymes. Without it, your body would not be able to release energy or make fats from carbohydrates. Vitamin B 3 is also used to make sex hormones and other important chemical signal molecules.
Vitamin B 3 comes in two principal forms: niacin (nicotinic acid) and niacinamide (nicotinamide). When taken in low doses for nutritional purposes, these two forms of the vitamin are essentially identical. However, each has its own particular effects when taken in high doses. Additionally, a special form of niacin called inositol hexaniacinate has shown some promise as a treatment with special properties of its own.
Niacin is one of the best researched of all the vitamins, and the evidence for using it to treat at least one condition—high cholesterol—is strong enough that it has become an accepted mainstream treatment.
Niacin has been used since the 1950s to improve cholesterol profile. Several well-designed double-blind, placebo-controlled studies have found that niacin can reduce LDL ("bad") cholesterol by approximately 10% and triglycerides by 25% while raising HDL ("good") cholesterol by 20% to 30%. ^ ^ ^ ^ ^ Niacin also lowers levels of lipoprotein(a)—another risk factor for atherosclerosis—by about 35%. Long-term studies have shown that use of niacin can significantly reduce death rates from cardiovascular disease. ^ Niacin appears to be a safe and effective treatment for high cholesterol in people with diabetes as well, and (contrary to previous reports) does not seem to raise blood sugar levels. ^
When a child develops diabetes, there is an interval called the honeymoon period in which the pancreas can still make some insulin and there is little to no need for injected insulin. Weak evidence suggests that niacinamide might slightly delay the onset of more severe symptoms. ^ A cocktail of niacinamide plus antioxidant vitamins and minerals has also been tried, but the results were disappointing in one study. ^ However, in another study, use of intensive insulin therapy along with niacinamide and vitamin E was more effective than insulin plus niacinamide alone in prolonging the honeymoon period. ^ A recent study suggests that niacinamide may also improve blood sugar control in type 2 (adult-onset) diabetes, but it did not use a double-blind design. ^ (For information on why this is important, see Why Does This Database Rely on Double-blind Studies? )
Double-blind studies involving a total of about 400 individuals have found that inositol hexaniacinate can improve walking distance for people with intermittent claudication . ^ ^ ^ For example, in one study, 100 individuals were given either placebo or 4 g of inositol hexaniacinate daily. ^ Over a period of 3 months, participants improved significantly in the number of steps they could take on a special device before experiencing excessive pain.
There is some evidence that niacinamide may provide some benefits for those with osteoarthritis . In a double-blind study, 72 people with arthritis were given either 3,000 mg daily of niacinamide (in 6 equal doses) or placebo for 12 weeks. ^ The results showed that treated participants experienced a 29% improvement in symptoms, whereas those given placebo worsened by 10%. However, at this dose, liver inflammation is a concern that must be taken seriously.
According to one small double-blind study, the inositol hexaniacinate form of niacin may be helpful for Raynaud's phenomenon . ^ The dosage used was 4 g daily—once again a dosage high enough for liver inflammation to be a real possibility.
The official US and Canadian recommendations for daily intake of niacin are as follows:
- 0-6 months: 2 mg
- 7-12 months: 4 mg
- 1-3 years: 6 mg
- 4-8 years: 8 mg
- 9-13 years: 12 mg
- 14 years and older: 16 mg
- 14 years and older: 14 mg
- Pregnant Women: 18 mg
- Nursing Women: 17 mg
Because the body can make niacin from the common amino acid tryptophan, niacin deficiencies are rare in developed countries. However, the antituberculosis drug isoniazid (INH) impairs the body's ability to produce niacin from tryptophan and may create symptoms of niacin deficiency. ^ Good food sources of niacin are seeds, yeast, bran, peanuts (especially with skins), wild rice, brown rice, whole wheat, barley, almonds, and peas. Tryptophan is found in protein foods (meat, poultry, dairy products, fish). Turkey and milk are particularly excellent sources of tryptophan.
When used as therapy for a specific disease, niacin, niacinamide, and inositol hexaniacinate are taken in dosages much higher than nutritional needs, about 1 to 4 g daily. Because of the risk of liver inflammation at these doses, medical supervision is essential.
Many people experience an unpleasant flushing sensation and headache when they take niacin. These symptoms can usually be reduced by gradually increasing the dosage over several weeks or by using slow-release niacin. However, slow-release niacin appears to be more likely to cause liver inflammation than other forms. Inositol hexaniacinate may also cause less flushing than plain niacin, and if you take an aspirin along with niacin, the flushing reaction will usually decrease.