Metabolite Encyclopedia › Antioxidant and cofactor
Ascorbic acid is vitamin C. Almost every other mammal manufactures its own in the liver. Humans carry a broken copy of the very last gene in that pathway, which is the only reason we have to eat it.
- Also calledVitamin C
- Made inNot by humans, the enzyme is gone
- Required forCollagen and neurotransmitter synthesis
- Cleared byThe kidneys, within hours
Three things worth knowing
One broken gene is the whole reason it is a vitamin. Dogs, cats, cows and rats all build vitamin C in the liver from glucose. Humans, other primates, guinea pigs and some bats carry a non-functional version of GULO, the last enzyme in that chain. Everything upstream still works. The final step does not, so the pathway dead-ends and the molecule has to arrive in food.
Your brain hoards it. Vitamin C is concentrated far more heavily in brain and adrenal tissue than in blood, and neurons actively pump it in against the gradient. It is a required cofactor for the enzyme that turns dopamine into noradrenaline, which puts it directly inside the chemistry of alertness.
Past a point you are buying expensive urine. The fraction of a dose that gets absorbed falls as the dose rises, and the kidneys clear what gets through. Plasma levels flatten out. This is one of the most reliably reproduced findings about any vitamin, and it is why the phrase keeps coming up.
Why more stops helping
Where you meet it in food
- Bell peppers
- Kiwi
- Broccoli
- Oranges
- Strawberries
- Brussels sprouts
Bell peppers and kiwi carry more per serving than oranges do, which surprises most people. Vitamin C is also fragile, so prolonged heat and long storage reduce what is left.
Questions people actually ask
Why can't humans make vitamin C?
A gene called GULO, which codes for the final enzyme in the synthesis pathway, is non-functional in humans. The rest of the pathway is still there. Only the last step is missing.
Is a high dose better?
Absorption efficiency falls as the dose rises, so the fraction that actually reaches your blood keeps shrinking while the amount leaving in urine keeps growing.
Does cooking destroy it?
Heat and long storage reduce it, and because it is water soluble, boiling moves a lot of it into the water. Raw and lightly cooked sources keep more.
Is it found in mushrooms?
It appears in AHARA's metabolomic map of its Reishi and Lion's Mane elixirs, which is how it ended up in this encyclopedia.
Ascorbic acid is one of more than 2,000 metabolites AHARA mapped across its Reishi and Lion's Mane elixirs. You can browse the rest of what is in the bottle.
Open the Metabolite EncyclopediaReferences
Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017;9(11):1211. doi:10.3390/nu9111211
Padayatty SJ, Levine M. Vitamin C: the known and the unknown and Goldilocks. Oral Dis. 2016;22(6):463-493. doi:10.1111/odi.12446
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