Restoring the Human Body’s Ability To Make Vitamin C
by Bill Sardi by Bill Sardi
Utilizing gene therapy, researchers at McMaster University in Hamilton, Ontario (Canada) report, for the first time, that they have successfully restored the ability to make vitamin C in a genetic strain of mice that no longer produces vitamin C as most animals do, suggesting a future day when this lost capability can be restored to humans.
Utilizing a harmless virus as a vector (delivery agent), a working copy of the gulonolactone oxidase gene was re-inserted into mouse liver cells and their ability to naturally produce vitamin C was restored, enough to increase their blood levels by 6-fold in just four days, and within 23 days blood concentrations were 20-fold higher. Gene therapy was so effective, vitamin C levels in the genetically defective mice were similar to normal mice who naturally produce vitamin C throughout the day.
Only a small number of animals, guinea pigs, fruit bats, primate monkeys and humans, do not produce vitamin C naturally by enzymatic conversion of blood sugar to ascorbate, the type of vitamin C that is continually produced in the liver of most animals. For example, a 160-pound goat, about the same weight as a human, will synthesize about 13,000 milligrams of vitamin C per day.
Modern humans, by comparison, produce no vitamin C and consume only about 110 milligrams of vitamin C from their daily diet. Early hunter-gatherers who foraged for food are believed to have consumed around 640 mg of vitamin C per day from fruits and vegetables.
Vitamin C deficiency is universal in humans and is caused by a single gene defect. This genetic defect is believed to have occurred long ago in human history and was transferred to all succeeding generations. The gene that makes the enzyme gulonolactone oxidase, which is currently found in all humans, is dysfunctional. This finding gives rise to speculation that early humans once produced their own vitamin C as most animals do today.
While humans can consume vitamin C supplements to boost vitamin C blood levels, it is often difficult to achieve high concentrations needed to prevent or even treat disease. Researchers speculate that if the ability to continually synthesize vitamin C in humans could be restored, humans would likely live far longer, and experience fewer cataracts, gallstones, aneurysms (bulging blood vessels), as well as less cancer, diabetes and heart disease.
Animals that produce vitamin C naturally live on average about 8—12 times beyond their age when childhood growth ceases. For comparison, humans live only 2—3.5 times beyond their age of physical maturation (~ age 18 years) and live about 60—75 years. This research suggests a day when humans might live hundreds of disease-free years of life.
This report comes on the heels of recent studies showing intravenous vitamin C therapy may be promising for treatment of cancer. The mouse gene therapy study was published in an advanced online edition of Human Gene Therapy.
Lead researcher Herb E. Schellhorn of the Department of Biology at McMaster University, said the future of this type of research may depend upon the acceptance of gene therapy altogether, since earlier gene therapy involving humans have been disappointing. But he reports researchers around the world are eager to learn more about his work and fellow researchers at McMaster University are vying to conduct further studies. Schellhorn is currently seeking funding to proceed with follow-up studies.
Reference: Human Gene Therapy, Sept 2, 2008, published ahead of print.