Symptoms of toxicity are seldom seen because any excess is simply excreted in the urine. However, a large amount of niacin blocks the release of free fatty acids so is contraindicated before athletic performance. This tends to reduce endurance. By stopping the burning of body fat it interferes with the weight loss that may be expected from exercising. Sources are liver, milk, eggs meat, green leafy vegetables, and whole grains.
Storage is very limited.
Excretion is through the urine. Your brain will not functions as well as it should if you skip breakfast.