The properties of a substance are determined by the structure of its component molecules. Vitamin C that is synthesized in the laboratory has exactly the same atoms joined together in exactly the same fashion as vitamin C that is made in an orange or a rose hip bush. As far as biological activity goes, the source of vitamin C is irrelevant. The cheapest version is as effective as the most expensive. Perhaps a more appropriate question is whether we should be taking vitamin C supplements.
There is a wealth of information suggesting that the human body benefits from vitamin C in excess of the roughly 20 mg daily needed to ward off scurvy. Population studies show that people who consume the most vitamin C from foods have reduced incidence of certain cancers, particularly stomach cancer. This likely reflects vitamin C's ability to reduce the formation of nitrosamines, known cancer causing substances. In a study that encompassed 65 counties in China, blood samples from randomly selected adults were analyzed for vitamin C. Those who had the highest levels were the least likely to develop cancer. Furthermore, it has been found that the vitamin C level in the white blood cells of cancer patients is unusually low and that the plasma vitamin C level of smokers is 43% lower than of non-smokers. This may explain why children of smokers have a greater risk of genetic diseases such as leukemia.
Bruce Ames, one of the leading cancer researchers in the world, discovered that sperm damage in men increases as vitamin C levels in the body drop. He discovered that below a daily intake of 60 mg, there is measurable damage to the DNA in sperm. Surveys show that half of all men of reproductive age consume less than this amount of vitamin C daily. If they are smokers, the problem is of course exacerbated. The antioxidant effect of vitamin C may also provide protection from heart disease. In the test tube, vitamin C can prevent the oxidation of LDL cholesterol; this oxidation has been linked with damage to coronary arteries. Epidemiological studies appear to bear out this observation. A study at the University of California analyzed the diet of 11,348 adults ranging in age from 25-74 in the early 1970's. Ten years later, men who had the highest intake of vitamin C had a 45% lower rate of heart disease. In a corroborating study, 747 Massachusetts residents who were 60 or older in the early 1980's had blood samples taken. A dozen years later, the heart disease rate was lowest among those who had the highest blood levels of vitamin C. The blood levels correlated with eating vegetables high in vitamin C.
There seems to be no doubt that vitamin C can help guard our health. It is even important in the functioning of vitamin E, which is oxidized in the process of carrying out its antioxidant activities. It is then reduced to its active form by vitamin C. But what is the optimal daily intake? The most comprehensive study to try and answer this question was carried out in 1996 at the National Institutes of Health in the US. Seven healthy young men agreed to live in a hospital ward for up to half a year. Their blood levels of vitamin C were depleted by putting them on a very low vitamin C diet. Then they were given doses of 30 mg, 60 mg, 100 mg, 200 mg, 400 mg, 1000 mg and 2500 mg a day to determine which dose would result in peak amounts in the blood and tissues. Doses greater than 200 mg per day did not increase vitamin C levels in the blood or tissues. At 1000 mg, oxalate began to show up in the urine indicative of the breakdown of excess vitamin C. The ballpark figure for optimal vitamin C intake was therefore judged to be in the 200-500 mg range daily. Since some of this comes from food, a supplement of 200 mg a day seems appropriate. Can there be any harm from vitamin C supplements at this dose? Most unlikely. Larger doses can cause diarrhea and cause a false negative result in fecal blood tests. They may also increase the risk of kidney stone formation through oxalate and can also enhance the absorption of iron from food which may be a problem for people who have undiagnosed iron overload disease, known as hemochromatosis. But no studies have shown any harm in the range of 200 mg a day.