Niacin (vitamin B3)
Niacin, also known as vitamin B3, helps:
release energy from the foods we eat
keep the nervous system and skin healthy
Good sources of niacin
There are two forms of niacin – nicotinic acid and nicotinamide – both of which are found in food.
What its good for:
As a cholesterol treatment, there are good studies showing that niacin can boost levels of good HDL cholesterol and lower triglycerides. Niacin also modestly lowers bad LDL cholesterol. It's often prescribed in combination with statins for cholesterol control, such as Crestor, Lescol, or Lipitor.
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:
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
Good sources of niacin include:
cooked skipjack tuna, 18.8 mg
cooked light meat turkey, 11.8 mg
cooked, lean ground pork, 11.1 mg
cooked venison, 10.8 mg
cooked, lean veal, 8.0 mg
Plant foods and spices
sesame seed flour, 12.5 mg
ground ginger, 9.6 mg
dried tarragon, 9.0 mg
dried, green sweet peppers, 7.4 mg
grilled portabella mushrooms, 6.2 mg
roasted sunflower seeds, 4.1 mg
dehydrated apricots, 3.6 mg
baked potato, 3.1 mg
Fortified breakfast cereals have among the highest niacin contents (more than 20 mg per 100 grams). Whole grain flours, such as from wheat, rice, barley or corn, and pasta have niacin contents in a range of 3–10 mg per 100 grams.
How much niacin do I need?
The amount of niacin you need is about:
16.5mg a day for men
13.2mg a day for women
You should be able to get all the niacin you need from your daily diet.
Niacin can't be stored in the body, so you need it in your diet every day.
Flushing usually lasts for about 15 to 30 minutes, though it can sometimes last up to two hours. It is sometimes accompanied by a prickly or itching sensation, in particular, in areas covered by clothing. Flushing can be blocked by taking 300 mg of aspirin half an hour before taking niacin, by taking one tablet of ibuprofen per day or by co-administering the prostaglandin receptor antagonist laropiprant. Taking niacin with meals also helps reduce this side effect. Acquired tolerance will also help reduce flushing; after several weeks of a consistent dose, most patients no longer experience flushing.Reduction of flushing focuses on altering or blocking the prostaglandin mediated pathway. Slow- or "sustained"-release forms of niacin have been developed to lessen these side effects. One study showed the incidence of flushing was significantly lower with a sustained-release formulation, though doses above 2 g per day have been associated with liver damage, in particular, with slow-release formulations.
Prostaglandin (PGD2) is the primary cause of the flushing reaction, with serotonin appearing to have a secondary role in this reaction. The effect is mediated by prostaglandin E2 and D2 due to GPR109A activation of epidermal Langerhans cells and keratinocytes. Langerhans cells use cyclooxygenase type 1 (COX-1) for PGE2 production and are more responsible for acute flushing, while keratinocytes are COX-2 dependent and are in active continued vasodilation.Flushing was often thought to involve histamine, but histamine has been shown not to be involved in the reaction.
Gastrointestinal and hepatic
Gastrointestinal complaints, such as indigestion, nausea and liver failure, have also been reported. Hepatotoxicity is possibly related to metabolism via amidation resulting in NAD production.The time-release form has a lower therapeutic index for lowering serum lipids relative to this form of toxicity.
Although high doses of niacin may elevate blood sugar, thereby worsening diabetes mellitus,recent studies show the actual effect on blood sugar to be only 5–10%. Patients with diabetes who continued to take anti-diabetes drugs containing niacin did not experience major blood glucose changes. Thus, overall, niacin continues to be recommended as a drug for preventing cardiovascular disease in patients with diabetes.
Hyperuricemia is another side effect of taking high-dose niacin and may exacerbate gout.
Side effects of heart arrhythmias have also been reported.Increased prothrombin time and decreased platelet count have been reported; therefore, these should be monitored closely in patients who are also taking anticoagulants
Particularly the time-release variety, at extremely high doses, can cause acute toxic reactions. Extremely high doses of niacin can also cause niacin maculopathy, a thickening of the macula and retina, which leads to blurred vision and blindness. This maculopathy is reversible after niacin intake ceases.
Niacin in doses used to lower cholesterol levels has been associated with birth defects in laboratory animals, with possible consequences for infant development in pregnant women.