Also known as ascorbic acid, vitamin C was isolated in 1928. This vitamin serves as an excellent antioxidant and could protect brain cells, including cells in the eye. The eye is highly susceptible to damage by sunlight, oxygen, various chemicals, and pollutants. Because of an aging Western world population and a continued depletion of ozone, having adequate antioxidants in the eye is very important. But how much vitamin C is enough to protect our cells? some nutritionists and doctors recommend 1,000 mg a day or more, but we think less is required. If you purchase a 1000 mg product, take only one pill two or three times a week.

What is the right dosage of vitamin C
Ever since Nobel Prize winner Linus Pauling extolled the benefits of megadosing with vitamin C, the medical community has been debating the optimal dosage intake of this vitamin. Linus Pauling won the Nobel Prize in chemistry as well as the Nobel Peace Prize. He died in 1994.
   Although many doctors stood firm for a long time asserting that the RDA of 60 mg for this vitamin was adequate, more and more doctors are now realizing that higher dosages can confer additional antioxidant benefits. However, the optimal daily intake of vitamin C has not yet been determined, nor is it likely to be determined soon. Nevertheless, we now suspect that excessive intake of vitamin C, expect perhaps in the therapy of a particular medical condition, may not be necessary. A study published in the American Journal of Clinical Nutrition points that large doses of ingested vitamin C may be excreted without being utilized. When the dosage of vitamin C given to a group of healthy men was increased from 200 mg a day to 2,500 mg a day, blood levels increased only negligibly. Blood levels of vitamin C generally reflect the levels found in the rest of the body.

Ideal daily dose of Vitamin C
If you ask a dozen doctors the question of the ideal vitamin C dosage, you are likely to get a dozen different answers. Those who have an excellent diet with plenty of fresh fruits (including citrus) and vegetables, they many not need to take any vitamin C supplements. Those whose diet is not ideal, it would seem reasonable to take between 50 to 300 mg once or twice a day, preferably a vitamin C formula that includes bioflavonoids.
   Vitamin C may be helpful for some people with heart disease and also may be helpful as an antioxidant for eyesight health.

Vitamin C and cancer
Vitamin C as a treatment for cancer was touted by Linus Pauling, Ph.D. in the 1970s. Dr. Linus Pauling reported that patients treated with high doses of vitamin C survived longer than those who did not receive vitamin C supplements. Studies in the 1970s first suggested the high doses of vitamin C could help treat cancer, but later research disputed these early claims. Every since then the role of vitamin C and cancer has been a topic of debate. In a  2005 study, published in the Proceedings of the National Academy of Sciences, researchers conducted laboratory experiments which simulated clinical infusions of vitamin C on a range of nine cancer and four normal cells. In five of the cancer lines, there was a 50% decrease in cell survival, while normal cells were unaffected. Lymphoma cells were the most sensitive to vitamin C. The effective dose was around four millimoles, a concentration much higher than an oral dose but easily achievable by intravenous infusion.
   Vitamin C boosts production of hydrogen peroxide, which kills cancer cells and leaves healthy cells unharmed. There is still more research that needs to be done in humans before we can be more confident on the role of vitamin C in cancer treatment or prevention.

Vitamin C and Cancer research - 2007
Vitamin C can impede the growth of some types of tumors. When vitamin C was given to mice that had been implanted with human cancer cells -- either the blood cancer lymphoma or prostate cancer, the vitamin undermined a tumor's ability to grow under certain conditions. The study was done by Dr. Chi Dang, a professor of medicine and oncology at Johns Hopkins University in Baltimore, and published in the Sept 2007 issue of Cancer Cell.

The ideal vitamin C dosage
Q. What's your opinion on ideal daily dose of Vitamin C?
   A. If you ask a dozen doctors this question, you are likely to get a dozen different answers. We would say that for those who have an excellent diet with plenty of fresh fruits (including citrus) and vegetables, they many not need to take any vitamin C supplements. For those whose diet is not ideal, it would seem reasonable to take between 50 to 300 mg once or twice a day, preferably a formula that includes bioflavonoids.

Deficiency in Canadian youth
As many as one in seven young Canadian adults may be vitamin C deficient, which could place them at increased risk for chronic health problems. Dr. Ahmed El-Sohemy, at the University of Toronto, and colleagues gathered information on diet, race/ethnicity, vitamin C supplement use, height, weight, waist size, body mass, blood pressure, and physical activity for 692 non-pregnant women and 287 men living on a university campus. Blood tests showed just more than half -- 53 percent -- had adequate levels of circulating ascorbic acid (vitamin C), while 33 percent had suboptimal levels, and the remaining 14 percent - one in seven - had deficient levels, which were defined as less than 11 micromoles per liter of blood. The results of the Dr. Ahmed El-Sohemy study by were published in American Journal of Epidemiology, August 15, 2009.

Production and manufacturing, source
Is the common source for manufacturing vitamin c products GMO corn?
    We are not sure, we focus our research on the clinical aspects of this vitamin and do not know for sure how different chemical manufacturers make it, they each may have a different process or source. When we searched online, we found one company that says, "The ultimate raw material for the production of vitamin C (ascorbic acid) is corn or wheat. This is converted via starch to glucose by specialist companies, and then to sorbitol. We produce the pure final products from sorbitol in a series of biotechnical, chemical processing and purification steps."

Vitamin C Research study
The effect of 5-year vitamin C supplementation on serum pepsinogen level and Helicobacter pylori infection.
Sasazuki S. National Cancer Center Research Institute East, Kashiwa 277-8577, Japan.
Cancer Sci. 2003 Apr;94(4):378-82.
We conducted a population-based, double-blind, randomized controlled trial to examine the effect of vitamin C supplementation on serum pepsinogen (PG) level, Helicobacter pylori (H. pylori ) infection, and cytotoxin-associated gene A (Cag A) status. Subjects aged 40 to 69 years living in one village in Akita prefecture, a high-risk area for gastric cancer in Japan, were recruited through annual health check-up programs. Among 635 subjects diagnosed as having chronic gastritis on the basis of serum PG levels, after excluding ineligible cases, 439 subjects were assigned to one of four groups using a 2 x 2 factorial design (0 or 15 mg/day beta-carotene and 50 or 500 mg/day vitamin C). However, based on the results from two beta-carotene trials in the United States, we discontinued beta-carotene (vitamin C supplementation was continued). Finally, 120 subjects in the low-dose group (vitamin C 50 mg), and 124 subjects in the high-dose group (vitamin C 500 mg) completed the 5-year supplementation. The difference in the change of PGI/II ratio between baseline and after 5-year follow up was statistically significant between the intervention groups among those who completed the supplementation: - 0.25 for the low-dose group and - 0.13 for the high-dose group. To conclude, vitamin C supplementation may protect against progression of gastric mucosal atrophy.

Q. Twice a week I use a yohimbe bark supplement and wonder if vitamin c with bioflavonoids will interact with it
   A. Vitamin C is a very safe supplement and can be taken together with almost all supplements.

Everytime I try to take Vit C supplements I get awful pain in my leg muscles. When I stop vitamin c, the pain stops. My room-mate had the same problem. Have you ever heard of this before? I am also studying to be a holistic nutritionist and have consulted all of my textbooks, but I see no mention about this. I was having adrenal problems and I started taking 1,000mg of Vit C a day, if I go down to 50mg a day, I am okay, without pain. Why would so much vit C cause pain in the top of thigh muscles?
    We have never heard of this potential side effect and have no idea. Perhaps trying a different brand may make a difference?