Vitamin C, or ascorbic acid, is a water soluble vitamin whose chemical structure is closely related to glucose. Most animals can, in fact, synthesise vitamin C from glucose and galactose sugars, but humans lack the enzyme (l-gulonolactone oxidase) needed for this conversion.
The only other animals who are unable to synthesise their own supplies of vitamin C are:
- Primates
- Guinea pigs
- The Indian fruit bat
- The Red-vented bulbul (an Asian songbird)
- Rainbow trout
- Coho salmon
- A single strain of Japanese laboratory rat.
Why our ancestors lost or never acquired the ability to synthesize vitamin C is one of the greatest mysteries of human biochemistry. It is thought to have resulted from a genetic accident occurring around 60 million years ago which, according to some scientists, mean we all suffer from a genetic disease, named hypoascorbaemia. This genetic defect may increase our risk of a number of common illnesses such as viral infections, raised cholesterol levels, coronary heart disease and cancer as well as reducing our ability to cope with stress. The goat, for example, which weighs around the same as an adult man, produces between 2g and 13 g of vitamin C per day depending on its levels of stress and illness.
