The following is quoted from NootropicExpert.com with written authorized permission.
Vitamin B3 (Niacin, nicotinic acid, 3-pyridine-carboxylic acid) is one of eight B-Vitamins. Niacin is a precursor to the coenzymes nicotinamide adenine dinucleotide (NAD), and nicotinamide adenine dinucleotide phosphate (NADP).
Vitamin B3 is known for increased alertness, clarity, focus, memory, enhanced mood, and energy, is a potent antioxidant and free radical scavenger, lowers LDL-cholesterol, increases HDL-cholesterol and lowers triglycerides
NAD is needed to catabolize fats, carbohydrates, proteins, and alcohol. And NAD is involved in cell signaling and DNA repair.
ATP provides the fuel for mitochondria in each of your cells. Not enough NADH leads to ATP depletion, which can eventually lead to cell death.
Studies have shown that supplementing with niacin improves cognitive function, enhances cellular energy, boosts cerebral circulation, increases endurance, switches ‘off’ aging genes, and extends lifespan.
Neurotransmitters. Niacin affects cognitive function by stimulating the production of dopamine, norepinephrine, and serotonin.[iii] These neurotransmitters are involved in memory, learning, cognition, recall, and mood.
NADH is the primary carrier of electrons from glucose and lactate for ATP synthesis. ATP is the fuel source for mitochondria. The power supply in each of your brain cells. So you need niacin to produce NADH to transfer the energy from the food you eat into a type of energy your body can use.