Niacin, also known as Vitamin B3, is important for the normal function of many bodily processes. Like other B vitamins, it is water-soluble and plays a role in turning food into energy, as well as in the metabolism of fats and carbohydrates. Niacin can also act as an antioxidant within cells, which means it can destroy cell-dam-aging free radicals. In conjunction with riboflavin and pyridoxine, it helps to keep the skin, intestinal tract and nervous system functioning smoothly.
The recommended daily allowance (RDA) of niacin for infants under six months is 5 mg. Babies from six months to one year of age require 6 mg. Children need 9 mg at one to three years of age, 12 mg at four to six years, and 13 mg at seven to 10 years. Women need 15 mg from 11-50 years, and 13 mg thereafter. Somewhat more is required for pregnancy (17 mg) and lactation (20 mg). Men require 17 mg from 11-14 years of age, 20 mg from 15-18 years, 19 mg from 19-50 years, and 15 mg at 51 years and older.
Niacin in the form of nicotinic acid can be taken in very large doses to decrease blood cholesterol levels and reduce the risk of heart attack. Niacin is an important part of the treatment of familial hyperlipidemia, an inherited disorder characterized by high blood cholesterol levels and increased risk of heart disorders. The amount of niacin required is between 2 and 3 g per day. Although treatment with niacin is considered the best strategy for normalizing blood cholesterol levels as of 2002, it should not be undertaken without professional medical advice and supervision. Niacin has been singled out as a dietary supplement for which people frequently exceed the upper limits of safe intake. One Canadian study found that 47% of adults who were taking dietary supplements were taking niacin above recommended levels.
Certain conditions preclude the use of high doses of niacin. These disorders include gout, diabetes, peptic ulcer, liver or kidney disease, and high blood pressure requiring medication. Even in the absence of these conditions, a patient on high doses of niacin should be closely monitored to be sure the therapy is both effective and without complications. A frequent side effect of this therapy is extreme flushing of the face and neck. It is harmless, but can be unpleasant. An alternative form of nicotinic acid that does not cause flushing is inositol hexaniacinate. "Slow release" niacin also causes less flushing, but should not be taken as there is higher risk of liver inflammation.
There is some evidence that niacinamide used on a long-term basis can prevent the onset of juvenile diabetes in many susceptible children. Those who have been newly diagnosed with juvenile diabetes may also benefit by extending the time that the pancreas continues to produce a small amount of insulin. The advice of a health care provider should be sought for these uses.
Inositol hexaniacinate can be helpful for people suffering from intermittent claudication. This condition causes leg pain with exercise due to poor blood flow to the legs. Dilation of the blood vessels caused by the inositol hexaniacinate relieves this condition to some extent, allowing the patient to walk farther with less pain.