There are two types of niacin, or vitamin B-3. These are niacinamide, also called nicotinamide, and nicotinic acid. You also get some niacin when you consume foods containing tryptophan, since your body converts tryptophan to niacin. Sources of niacin include eggs, fish, meat, milk, yeast, grains and green leafy vegetables. Although you need some niacin to stay healthy, too much niacin can cause toxicity symptoms.
Recommended Intake
For adults, the recommended dietary allowance for niacin from all sources is 14 mg per day for women and 16 mg per day for men, and the tolerable upper intake level is 35 mg per day. Keeping your niacin intake between these two amounts will limit the risk for either deficiency or toxicity symptoms. Only exceed the tolerable upper intake level under a doctor's supervision due to the risk of serious side effects from higher doses.
Side Effects
Niacinamide side effects may include dizziness, stomach upset, nausea, gas, jaundice, vomiting, mouth pain, gout, irregular heartbeat, vision loss, ulcers, liver toxicity and a decrease in insulin sensitivity, especially at doses above 2 to 3 g per day. However, niacinamide is usually better tolerated than nicotinic acid and doesn't cause the flushing in most people that is common with nicotinic acid.
Safety
Women who are pregnant, children, people who are going to have surgery and people with allergies, diabetes, gout, heart disease, ulcers, low blood pressure, liver disease or gallbladder disease should not take high doses of niacinamide or niacin unless they are under the supervision of their doctor. Niacinamide can also interact with certain medications, including those for high cholesterol, diabetes, gout, primidone and carbamazepine.
Considerations
Niacinamide and nicotinic acid have different effects on the body. Do not take niacinamide to lower cholesterol, because only nicotinic acid is effective for this use. It is best to get your recommended niacin intake from foods because there isn't a risk for toxicity from the niacin in the amount consumed in foods.
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