Niacin and its amide form niacinamide both make up vitamin B3. Although many people consider them equivalents, niacinamide has fewer therapeutic uses. Recommended dosages vary with age, gender and state of health.
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Once absorbed in the body, dietary niacin is converted from its parent form, nicotinic acid, into its amide form, niacinamide. Niacinamide helps release energy from fats, carbohydrates and proteins. Good food sources of niacin include animal proteins, beans, green vegetables, liver, mushrooms, peanuts, whole wheat, unpolished rice and enriched flours. Although milk and eggs do not contain niacin, they are rich in tryptophan. According to the Rx Med website, your body can also produce about 1 mg of niacin by converting 60 mg of dietary tryptophan.
Dosage recommendations for vitamins are referred to as reference daily intakes (RDI). According to the clinical reference MD Consult, men and adolescent boys should get 16 mg of niacinamide per day, while women and adolescent girls need 14 mg. If you're a pregnant or breast-feeding woman, the recommended dosages increase to 18 mg and 17 mg, respectively.
Certain disease states significantly raise niacinamide requirements. Pellagra, for instance, is a state of niacin deficiency that produces symptoms of diarrhea, dermatitis and dementia. Pellagra may result from a diet that is low in protein and niacin, isoniazid therapy or diseases that disrupt tryptophan utilization in your body. According to MD Consult, if you're an adult with manifestations of pellagra, you may need up to 500 mg of oral niacinamide per day, depending on the severity of your deficiency. Pellagra, however, is extremely rare in the United States today.
Although niacin has known applications in the treatment of several diseases, there's an important distinction to make between its two forms, nicotinic acid and niacinamide. For instance, physicians at MD Consult describe nicotinic acid as an effective adjunct in the treatment of peripheral vascular disease, circulatory disorders and ringing in the ears, as well as high blood cholesterol and triglycerides. In contrast, niacinamide has not proven effective in any of those disorders.
Taking enough niacinamide or niacin to meet RDIs does not produce adverse effects, according to MD Consult. However, if you take large amounts, it can cause flushing, itching, burning, tingling, stomach upset, dizziness, heart rate changes, fainting, headache, blurred vision and dental pain. Chronic overdosage can lead to gout, peptic ulcer, vision changes, high blood sugar and panic. The severity of niacin's side effects tends to increase when it's combined with other medications, particularly the cholesterol-lowering statins.