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What is Niacin? Energy!What is Niacin?
Niacin, also known as vitamin B3 (it was the 3rd B vitamin to be discovered) is an essential nutrient required to harvest the energy contained in sugars (carbs), fats and proteins. It's normally obtained in the diet via niacin, nicotinic acid or nicotinamide. Furthermore, the amino acid tryptophan can be used to make the same essential coenzymes. These molecules are chemically altered and serve as portions of essential coenzymes required for energy metabolism... • Nicotinamide Adenine Dinucleotide (NADH) • Nicotinamide Adenine Dinucleotide phosphate (NADPH) These required molecules work with many different enzymes of energy metabolism serving to add or remove electrons from a reaction. The main example here would be glycolysis, the citric acid cycle and oxidative phosphorylation as described in the carbohydrate metabolism page. How Does Niacin Work To Harvest Energy? The entire energy-harvesting system is driven by the proportion of NADH/NAD+ ratio (where NAD+ is the same as NADH, but with the hydrogen atom removed). For energy to be made, this ratio of NADH/NAD+ must be low. What I mean is, when there's lots of NADH around, this is an indication to your body that there isn't much energy being used since NADH is needed to produce ATP (your body's main energy currency). If you're not producing ATP for energy, NADH builds up (since it's not being used) and the metabolism of carbohydrates and proteins are driven elsewhere (or the path of least resistance!). One such path would be towards the synthesis of fats or nucleotides (for the creation of new cells and tissues). This is a regulatory mechanism your body uses to prevent excessive energy expenditure. If the metabolism of sugars and proteins continued regardless of the NADH/NAD+ ratio, we wouldn't be able to survive any extended period of time without food. When your body doesn't have the need for energy, sugars and proteins are more likely diverted to fat storage than nucleotide synthesis (of course, depending on the needs of your body). Alternatively, NADPH is used mainly for the synthesis of fats. It's produced through the metabolism of "other" sugars like sedoheptulose, ribulose and xylulose. This process is called the hexose monophosphate pathway (HMP). Oxidative Phosphorylation This is series of reactions occuring in the mitochondria involving NADH (and FADH2, from the metabolism of riboflavin). It's the bread and butter of the whole process of producing energy! In the membrane of mitochondria, you'll find a chain of enzymes commonly called the electron transport chain. In a nutshell, electrons are shuttled from NADH (which was generated in the citric acid cycle) to this system of enzymes. Various transport proteins and coenzymes move these electrons through the system, producing an electrical gradient across the mitochondrial membrane. You know, a voltage difference between the each side of the membrane. At the end of the chain, there's an enzyme called ATP synthase (a.k.a. Complex V) which contains a channel for the gradient to dissipate. As the channel opens and current flows through, this electrical energy is used to create molecules of ATP that drive your very existence! So, next time you're faced with the question, "What is niacin?" Think energy production! Niacin is absolutely required for life to continue. But, as with anything else, don't go overboard with it! Your body can only use so much niacin as there are symptoms of niacin overdose. On the flip side, you can also be deficient in the vitamin. To be on the safe side, make sure you're eating a balanced diet and you should get plenty of the vitamin. There are lots of niacin food sources from milk, lean meats, whole grains and some organ meats (especially from the liver). Recommended Daily Allowance Your daily intake of niacin depends on age, gender and physical state. Use the table below for a reference on how much niacin you should get on a daily basis...
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