Why humans need optimal doses of vitamin C every day

It’s winter in New Zealand and many of us are reaching for the vitamin C in the hope that we may ward of the ills and chills associated with this time of year.

Did you know that the only mammals on the planet that don’t make vitamin C in their bodies are humans, primates, guinea pigs and fruit bats?

In the body of a vitamin C-making mammal, the vitamin C molecule is made from a few small modifications to the glucose molecule. While glucose is in abundant supply in humans and animals, there are four enzymes that are required to convert glucose into vitamin C. Humans have only three of these enzymes, having lost the ability to make the fourth L-gulonolactone oxidase somewhere in evolution.

Of the four mammals mentioned above, only the human has changed his dietary preferences and humans are the only species to eat meat and be unable to produce their own vitamin C. Gorillas, guinea pigs and fruit bats seem to know by instinct that to stay healthy they must ingest large quantities of foods containing vitamin C.

In mammals that retained the ability to make vitamin C, it is made in response to all sorts of stress, especially the stress of infection. Under stress, that amount can be very significantly increased. A goat for instance can make up to 200 mg/kg on a daily basis but up to 100,000mg of vitamin C daily if under stress.

Why is it then that the RDA (recommended daily allowance) for humans is 1mg/kg approx 60 to 90mg per day? If vitamin C is so important to animals why do humans require so little? This is a very important question. Anyone who takes even the slightest interest in vitamin C would soon realise that humans have been very significantly short changed.

RDA would be a more appropriately ridiculous daily allowance and perhaps the reason why diseases so prevalent in humans are almost non existent in animals that make large amounts of vitamin C.

It is very interesting to note that mammals that make their own vitamin C can live 8-10 times beyond their age of physical maturity. Mammals without this ability have a difficult time reaching three to four times.

It is even more interesting to contemplate the impact on mankind if it were possible to re-install the L-gulonolactone oxidase enzyme in humans? In a study conducted by Sato et al in 1966, researchers administered this enzyme (harvested from chickens or rats) to guinea pigs on a vitamin C deficient diet. The guinea pigs survived and Dr Thomas Levy in his fascinating and thought provoking book ‘Vitamin C - Curing the Incurable’ suggests that this research “should stimulate further research into the feasibility of giving such direct enzyme replacement therapy to humans.”

It is incredibly rare according to Dr Levy for an inborn error in metabolism to be shared by all humans. Considering anecdotal evidence that one hears about a certain individual living to 100 while smoking and drinking every day, Dr Levy agrees that one can be blessed with a very efficient immune system but he suggests that “the ability to synthesize L-gulonolactone oxidase, at least to a limited degree, could also be the reason for an otherwise incredibly long and healthy life.”

To give credence to this, a study that emanated from UCLA in 1992 involving 11,348 participants over a 10-year period showed that men with the highest blood levels of vitamin C lived six years longer than those with the lowest levels.

APPLETON ASSOCIATES, T: 09 489 9362, john@johnappleton.co.nz,