Niacin, also known as Vitamin B3, is a water-soluble vitamin that functions as a coenzyme to help release energy from the food you eat. Unlike the other B vitamins, niacin is unique because it can be synthesized from the amino acid (building block of protein), tryptophan. This means that protein-rich foods such as meat, poultry, fish, eggs and peanut butter may also be considered niacin foods.
Niacin is more likely to survive the heat of cooking than most water-soluble vitamins, which are very susceptible to destruction during cooking.
Water-soluble vitamins, as the name suggests, can be dissolved in water, so they are absorbed directly into your blood stream. They travel freely though the blood to the places in your body where they are needed and any excess can be filtered by the kidneys and excreted through the urine.
Over the last few years, researchers have studied the effect of taking niacin for the prevention of heart disease. The results have been promising; however, the downside of this approach is that large doses of niacin can be toxic.
As a practical matter, eating niacin-rich foods will have a beneficial effect, without the risk of toxicity. Eating healthy, in general, is very good for your heart, and niacin seems to be one of those nutrients that you should look for in the foods you choose.
Note: Look at the discussion of "precursors" below for more information about niacin sources.
Here is a list of foods that are a good source of niacin.
Food Sources of Niacin
Fortified cereals and grain and products made from them
Peanuts and peanut butter