Vitamin B3

Vitamin B3 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 B3 is also used to make sex hormones and other important chemical signal molecules. Vitamin B3 comes in two principal forms: niacin (nicotinic acid) and niacinamide (nicotinamide). When taken in low doses for nutritional purposes, they are essentially identical. However, each has its own particular effects when taken in high doses. High-dose niacin is principally used for lowering cholesterol. High-dose niacinamide may be helpful in preventing type 1 (childhood-onset) diabetes and reducing symptoms of osteoarthritis. However, there are concerns regarding liver inflammation when any form of niacin is taken at high dosages. Additionally, good evidence suggests that a special form of niacin, inositol hexaniacinate, can improve walking distance in intermittent claudication. It may also reduce symptoms of Raynaud's phenomenon.

The official U.S. and Canadian recommendations for daily intake of niacin are as follows:

• Infants 0–6 months, 2 mg 7–12 months, 4 mg
• Children 1–3 years, 6 mg 4–8 years, 8 mg 9–13 years, 12 mg
• Males 14 years and older, 16 mg
• Females 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 bodys ability to produce niacin from tryptophan, and may create symptoms of niacin deficiency (see Interactions You Should Know About).
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. For prevention of diabetes in children, the usual dosage of niacinamide is 25 mg per kilogram body weight per day. There are 2.2 pounds in a kilogram, so a 40-pound child would get about 450 mg daily. Warning: Medical supervision is essential before giving your child long-term niacinamide treatment. 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.

There is no question that niacin (but not niacinamide) can significantly lower total cholesterol and LDL (bad) cholesterol and raise HDL (good) cholesterol. However, unpleasant flushing reactions and the risk of liver inflammation have kept niacin from being widely used (see Safety Issues). Growing evidence suggests that if used very carefully, niacin can be profitably combined with standard therapies for elevated cholesterol (see Safety Issues). Intriguing evidence suggests that regular use of niacinamide (but not niacin) may help prevent diabetes in children at special risk of developing it. Risk can be determined by measuring the ratio of antibodies to islet cells (ICA antibody test). Niacinamide may improve blood sugar control in both children and adults who already have diabetes. According to several good-size double-blind studies, inositol hexaniacinate may be able to improve walking distance in intermittent claudication (severe leg cramps caused by hardening of the arteries). Preliminary evidence suggests that inositol hexaniacinate may be able to reduce symptoms of Raynauds phenomenon as well. This condition includes an extreme response to cold, usually most severely in the hands. Preliminary evidence suggests that niacinamide may be able to reduce symptoms of osteoarthritis. Niacinamide may also reduce symptoms of polymorphous light eruption, a type of photosensitivity. Very weak evidence suggests one of the several forms of niacin may be helpful in bursitis,18cataracts,19HIV infection pregnancy and tardive dyskinesia.

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. High Cholesterol/Triglycerides Niacin has been used since the 1950s to lower harmful blood lipids (cholesterol, triglycerides, and lipoproteins) and to raise levels of HDL (good) cholesterol. Several well-designed double-blind placebo-controlled studies have found that niacin reduced LDL cholesterol by approximately 10%, triglycerides by 25%, and raised HDL cholesterol by 20 to 30%. Niacin also lowers levels of lipoprotein (a)—another risk factor for atherosclerosis—by about 35%. Furthermore, long-term use of niacin has been shown to 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. Preventing Diabetes A large study conducted in New Zealand suggests that niacinamide can help prevent high-risk children from developing diabetes. In this study, more than 20,000 children were screened for diabetes risk by measuring ICA antibodies. It turned out that 185 of these children had detectable levels. About 170 of these children were then given niacinamide for 7 years (not all parents agreed to give their children niacinamide or stay in the study for that long).About 10,000 other children were not screened, but they were followed to see whether they developed diabetes. The results were positive. In the group in which children were screened and given niacinamide if they were positive for ICA antibodies, the incidence of diabetes was reduced by almost 60%. These findings suggest that niacinamide is an effective treatment for preventing diabetes. (The results also indicate that tests for ICA antibodies can accurately identify children at risk for diabetes.) At present, an very large, long-term trial called the European Nicotinamide Diabetes Intervention Trial is being conducted to definitively determine whether regular use of niacinamide can prevent diabetes. Results from the German portion of the study have been released, and they are not positive. However, until the entire study is complete, it is not possible to draw conclusions. Treating Diabetes When a child develops diabetes, there is an interval called the honeymoon period in which the pancreas can still make some insulin, and insulin needs are low. 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. 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. Intermittent Claudication 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. Osteoarthritis There is some evidence that niacinamide may provide some benefits for those with osteoarthritis. In a double-blind study, 72 individuals 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. Raynauds Phenomenon 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, again a dosage high enough for liver inflammation to be a real possibility.

When taken at a dosage of more than 100 mg daily, niacin frequently causes annoying skin flushing, especially in the face. This reaction may be accompanied by stomach distress, itching, and headache. In studies, as many as 43% of individuals taking niacin quit because of unpleasant side effects. A more dangerous effect of niacin is liver inflammation. Although some reports suggest that it occurs most commonly with slow-release niacin, it can occur with any type of niacin when taken at a daily dose of more than 500 mg (usually 3 g or more). Regular blood tests to evaluate liver function are therefore mandatory when using high-dose niacin (or niacinamide or inositol hexaniacinate). This reaction almost always goes away when niacin is stopped. If you have liver disease, ulcers (presently or in the past), or gout, or drink too much alcohol, do not take high-dose niacin except on medical advice. Contrary to previous reports, niacin does not appear to raise blood-sugar levels in people with diabetes. Combining high-dose niacin with statin drugs (the most effective medications for high cholesterol) further improves cholesterol profile by raising HDL (good) cholesterol. Unfortunately, there are real concerns that this combination therapy could cause a potentially fatal condition called rhabdomyolysis. A growing body of evidence, however, suggests that the risk is relatively slight in individuals with healthy kidneys. Furthermore, even much lower doses of niacin than the usual dose given to improve cholesterol levels (100 mg versus 1000 mg or more) may provide a similar benefit. At this dose, the risk of rhabdomyolysis should be decreased. Nonetheless, it is not safe to try this combination except under close physician supervision. Rhabdomyolysis can be fatal. Another potential drug interaction involves the anticonvulsant drugs carbamazepine and primidone. Niacinamide might increase blood levels of these drugs, possibly requiring reduction in drug dosage. Do not use this combination except under physician supervision. The maximum safe dosage of niacin for pregnant or nursing women has been set at 35 mg daily (30 mg if 18 years old or younger).

If you are taking:

• Cholesterol-lowering drugs in the statin family, niacin might offer potential benefits: however, there are real dangers to this combination. Do not try it except under physician supervision.
   
• The antituberculosis drug isoniazid (INH): You may need extra niacin.
   
• Anticonvulsant drugs such as carbamazepine or primidone: Do not take niacinamide except under physician supervision.

If you drink alcohol excessively:

• Do not take niacin except under physician supervision.