A vitamin is an organic compound needed in small quantities that cannot be made in cells. In human nutrition , most vitamins function as coenzymes after modification; for example, all water-soluble vitamins are phosphorylated or are coupled to nucleotides when they are used in cells.  Nicotinamide adenine dinucleotide (NAD + ), a derivative of vitamin B 3 ( niacin ), is an important coenzyme that acts as a hydrogen acceptor. Hundreds of separate types of dehydrogenases remove electrons from their substrates and reduce NAD + into NADH. This reduced form of the coenzyme is then a substrate for any of the reductases in the cell that need to reduce their substrates.  Nicotinamide adenine dinucleotide exists in two related forms in the cell, NADH and NADPH. The NAD + /NADH form is more important in catabolic reactions, while NADP + /NADPH is used in anabolic reactions.
Eating enough protein, for example, is tied to a strong metabolism, as are some spicy foods and also drinking natural forms of caffeine in moderation, like coffee or tea. Packing in healthy high-protein snacks and sources throughout the day — in the form of wild-caught fish, cage-free eggs, grass-fed beef or raw dairy products, for example — is one the simple metabolism boosters that also keeps you full for longer. Protein is beneficial for keeping energy and blood sugar stable while also helping build calorie-burning lean muscle mass. ( 7 ) Eating foods with protein naturally forces your body to use up more calories during the digestion process than when you eat carbs.