The Alliance For Natural Health
Jonathan Wright, M.D.’s Green Medicine Article…

A Genetic Defect We All Share—The Human Need for Vitamin C



  • Animals show us why we need vitamin C
  • How much vitamin C is needed daily for optimal health?

How much vitamin C should we take every day? Can’t we get enough of this nutrient from orange juice? It’s not widely known that the answer to these questions is found in textbooks of human genetics, not just in textbooks of nutrition. That makes the answer a little long, but it’s definitely worth knowing!

An ever-increasing number of studies report the benefits of vitamin C supplementation. As encouraging as these reports are, they’re still looking at “details” instead of the “big picture,” or as the cliché goes, “not looking at the forest because of the trees.” As textbooks of human genetics, pediatrics, and internal medicine all tell us, the human requirement for vitamin C is not strictly a matter of nutrition, but rather a basic genetic defect, a biochemical inability to manufacture vitamin C internally that all humans share.

Vitamin C is synthesized internally by all species of animals, excepting only chimpanzees, monkeys and other “primate” species, guinea pigs, an obscure bat found only in India, and humans. Cats, dogs, elephants, birds, horses, cows…. nearly all other species need no vitamin C in their diets at all! Nearly all other animals synthesize vitamin C internally, from glucose (blood sugar) by an identical-to-all-species series of four enzymes. When stressed in any way, all other animals immediately start to self-manufacture greatly increased quantities of vitamin C to combat that stress.

Human liver cells contain the first three enzymes in the vitamin C synthesizing series, but the fourth enzyme is totally missing! When humans are stressed, the activity of those first three enzymes is greatly increased, but no vitamin C is produced since that fourth enzyme is missing from humans. Unlike animals, we are genetically prevented from producing one of the most important anti-stress and detoxifying molecules present in all of nature, vitamin C. The human need for vitamin C is an “inborn error of metabolism,” a fortunately survivable genetic disease, and not just a nutritional problem. This fact must be included in the “big picture” concerning vitamin C and optimal health. It’s obvious to those who take this approach that we’d all be considerably healthier, and live longer, if we didn’t all have this genetic problem.

When animals ingest carcinogens, their bodies immediately start to synthesize ten, twenty, fifty times as much vitamin C to help detoxify and get rid of the carcinogen. Human bodies “try” to make more vitamin C, but can’t.

When animals are injured, their bodies synthesize much more vitamin C to aid in tissue repair. (Vitamin C is key to the synthesis of collagen in “connective tissue”). Human bodies “try,” but can’t.

When animals are given drugs of any kind (including alcohol, nicotine, caffeine) their bodies synthesize much more vitamin C until the drugs are detoxified. Human bodies “try,” but can’t.

I could go on and on with examples but our space is limited. To summarize: when other animals start to become ill in any way, their bodies begin to synthesize much more vitamin C in an effort to head off the illness, and to shorten it or at least lessen the symptoms over time if it occurs.

One human study (which in a very practical way “summarizes” all of this and more) demonstrated that longevity is increased by daily supplementation of vitamin C, six years for the men involved, and one year for the women. Since this study was started when the participants were in middle age or older, it’s very likely that results would be much better if vitamin C supplementation was started at birth!

Mainstream medicine is actively in favor of treating all other genetic diseases to the maximum extent possible, but (for mostly political reasons) is silent on the subject of full correction of this one. Fortunately, we can (and should) take care of it on our own. And it’s easy: just take supplemental vitamin C! What little is present in our food is enough to prevent death from scurvy (a total lack of vitamin C), but not nearly enough to produce maximum health benefits.

A few scientists who’ve seriously studied this question point out that on an “equivalent-weight” basis with animals that synthesize their own vitamin C, healthy adult humans would (if not for our genetic defect) produce from 2 to 4 grams of vitamin C daily. Other scientists have observed that adult gorillas (another non-vitamin C synthesizing species) living in an area identical to the “original” human environment eat approximately 3 to 4 grams vitamin C daily (calculated on a human-weight basis).

These comparisons give us general guidelines about appropriate supplemental quantities, but since we’re all individuals, I recommend an individualized approach, using “feedback” from our own bodies. Popularized by Linus Pauling Ph.D as the “bowel-tolerance” approach, it’s quite simple. Slowly increase the amount of supplemental vitamin C each day until we start getting excess gas or loose bowels. At that point, our bodies are very likely not able to use that quantity, so “back off” to the largest amount tolerable without producing “loose bowels” or excess gas. Most adults I work with find the “tolerance point” to be 3 to 6 grams daily. However, when illness occurs, the tolerance point frequently increases to 20 to 30 grams or more daily, showing that our bodies “need the extra help” when we’re ill. Occasionally, people who’ve had severe viral illness have told me they’ve taken up to 100 grams daily for a day or two without any bowel problems at all.

Since vitamin C is water-soluble and rapidly used by our bodies, it’s logical to “spread it out” to at least two or three intervals daily when we’re healthy, and as often as hourly when we’re ill.

To “download” for free a much more complete explanation of “bowel tolerance” dosing, “go to”

There’s just one definite precaution about daily vitamin C use: individuals who have formed calcium oxalate kidney stones, or who come from families who’ve had them, should limit supplemental vitamin C to 1 gram daily unless they’re working with a health care professional knowledgeable in nutritional therapy.

There’s a very remote possibility that more vitamin C will increase the production of oxalate in those individuals. Fortunately, it’s easy to test for this possibility. If found—remember, this circumstance is rare—it’s also possible to prevent these extremely rare potential cases of vitamin C-induced calcium oxalate kidney stones.