Niacin is a part of the vitamin B complex, along with other B vitamins including Vitamin B1 (thiamine), Vitamin B2 (riboflavin) and more.

Functions

Niacin is an important vitamin for maintaining a healthy cardiovascular system and metabolism- especially balancing blood cholesterol levels. In addition niacin helps with brain function, healthy skin formation and maintenance and even preventing or treating diabetes. Niacin helps with Joint Mobility and to Treat Arthritis, treats Pellagra, a Disease Caused by Low B Vitamin Levels, Prevent Impotence (Erectile Dysfunction).

Rich Foods
1) Turkey – 1 breast: 101 mg (over 100% DV)
2) Chicken breast-3 oz: 8.9 mg (44% DV) 
3) Peanuts – 1 cup: 21.9 mg (over 100% DV)

4) Mushrooms – 1 cup: 7.6 mg (34% DV) 
5) Liver – 1 slice: 11.9 mg (60% DV)

6) Tuna – 3 oz: 11.3 mg (56% DV)
7) Green peas- 1 cup: 3 mg (15% DV) 

8) Grass-fed Beef – 30z: 7.6 mg (36% DV)

9) Sunflower seeds – 1 cup: 3.8 mg (19% DV) 10) 3-1 whole fruit: 3.5 (17% DV)

etc..

Overdose

Niacin overdose signs and symptoms include:
Severe skin flushing combined with dizziness
Rapid heartbeat
Itching
Nausea and vomiting
Abdominal pain
Diarrhea
Gout

Deficiency

 Vitamin B3
Indigestion, fatigue, canker sores, vomiting, depression, Severe deficiency, called pellagra, can cause symptoms related to the skin, digestive system, and nervous system.