Niacin, also known as nicotinic acid or vitamin B3, is an essential nutrient that plays a vital role in the body's metabolism. It is one of the eight B-vitamins that are responsible for converting food into energy. Niacin is classified as a water-soluble vitamin, meaning it is not stored in the body and needs to be replenished regularly through diet or supplementation.

Niacin is involved in various metabolic processes, including the breakdown of carbohydrates, fats, and proteins, and the synthesis of DNA. It also plays a crucial role in the production of energy by helping convert food into glucose. Additionally, niacin helps maintain the health of the nervous system, skin, and digestive system.

Key Points:
- Niacin is also known as nicotinic acid or vitamin B3.
- It is one of the eight B-vitamins responsible for converting food into energy.
- Niacin is classified as a water-soluble vitamin.
- It needs to be replenished regularly through diet or supplementation.
- Niacin is involved in various metabolic processes, including the breakdown of carbohydrates, fats, and proteins.
- It plays a crucial role in the production of energy.
- Niacin helps maintain the health of the nervous system, skin, and digestive system.

In terms of dietary sources, niacin can be found in both plant and animal-based foods. Some of the best food sources of niacin include meat, poultry, fish, legumes, whole grains, and nuts. Fortified cereals and breads also often contain added niacin. However, it is important to note that the niacin content in food can vary depending on factors such as processing and cooking methods.

Key Points:
- Niacin can be found in both plant and animal-based foods.
- Some of the best food sources include meat, poultry, fish, legumes, whole grains, and nuts.
- Fortified cereals and breads may also contain added niacin.
- The niacin content in food can vary depending on factors such as processing and cooking methods.

Deficiency of niacin can lead to a condition called pellagra, which is characterized by symptoms such as dermatitis (skin inflammation), diarrhea, dementia, and even death if left untreated. Pellagra was once a widespread disease, particularly in regions where corn was the staple food, as corn lacks sufficient niacin unless it is prepared and consumed in a specific way. However, pellagra is now rare in developed countries due to improved diets and fortified foods.

Key Points:
- Deficiency of niacin can lead to pellagra.
- Pellagra is characterized by symptoms such as dermatitis, diarrhea, and dementia.
- Pellagra was once widespread in regions where corn was the staple food.
- Pellagra is now rare in developed countries due to improved diets and fortified foods.

In conclusion, niacin, also known as vitamin B3, is an essential nutrient that plays a crucial role in various metabolic processes. It is involved in energy production, the breakdown of carbohydrates, fats, and proteins, and the maintenance of a healthy nervous system, skin, and digestive system. Niacin can be obtained from a variety of food sources, and its deficiency can lead to pellagra.