Everything about vitamin B3 and vitamin in nad

Update:2023-07-12   

vitamin in nad exist in food?

Food in itself is a complex material which is composed of proteins, carbohydrates, fats, water, minerals and vitamins. When we consume food, it is broken down to simpler compounds that our body can absorb to provide us with nutrition.

The vitamins besides other functions also acts as coenzyme which means, they mediate a reaction in our body cells. The coenzymes mentioned are produced at cellular level to take part in certain pathways that our body cells carry out. For these coenzymes to exist as it is in the food is not possible because they are highly sensitive to either light, acid, base or temperature. Any kind of food processing might render them inactive. And therefore there are precursors of these conenzymes (nad vitamin precursor) that are available in the food which when broken down in our body produce the coenzymes.

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Is NAD+ a vitamin B3?

Yes. NAD+ and NADH are fully coenzymated B3.

NAD+ is the oxidized partner of the redox couple for vitamin B3. NAD+ reduces to NADH by the addition of hydride (H-minus) from the Krebs cycle. After donating its electron to mitochondrial Complex I or to NADP+, NAD+ is regenerated, ready to participate in the next redox cycle.

[BTW, redox is a reverse contraction of OXidation and REDuction, the opposite process to oxidation.]

The synthesis of NAD from niacin and niacinamide is problematic and inefficient. It takes large amounts of niacin and niacinamide to make NAD. This is why the RDA for niacin is quite high compared to other Bs.

Another route of NAD synthesis from tryptophan, but this is also inefficient. Roughly a third of NAD+ is made from tryptophan.

The reason that niacin and niacinamide are the common forms of vitamin B3 in vitamin supplements is their chemical stability. They are very stable. NAD breaks down if you look at it cross-eyed. And tryptophan is unreliable for making B3 and can result in quinolinic acid, which has neurotoxic properties.

NAD+ and NADH supplements are available, but they are expensive. Their instability against hydrolysis means that they have to be absorbed sublingually, or delivered in enterically coated (waxy) tablets.

NAD+ and NADH both have first cousins: NADP+ and NADPH. One may difference in their roles is that NAD+ is higher in concentration than NADH, and with NADP+, it the other way around. So, in essence, NAD+ is shuttling reducing equivalents (immediately passing them from the Krebs cycle to oxidized molecules) while NADPH is storing them for later transfer.

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 In summary

NAD+ is synthesized from the B vitamin niacin.

FAD is synthesized from the B vitamin riboflavin.

Coenzyme A is synthesized from the B vitamin pantothenic acid.

ATP is not a derivative of any of the B vitamins, but is synthesized de novo by cells. However, the B vitamins thiamine and folate are required in the synthesis of ATP.