It seems that anything that is not “natural” is destined to be labelled in the pile of ingredients that are deemed to be possibly cancerous. So is there any truth to this?
The answer is NO. But first lets examine where this rumour came came from. The rumour came from this study : “Vitamin C-Induced Decomposition of Lipid Hydroxyperoxides to Endogenous Genotoxins“.
This study shows that lipid hydroperoxides (rancid fat molecules) can react with vitamin C to form products that could potentially harm DNA. Now here’s the kicker….these results of DNA damage were not demonstrated in the study. It was suggested that vitamin C can form genotoxins (DNA-damaging agents) from lipid hydroperoxides, the implication being that vitamin C may enhance mutagenesis and the risk of cancer.
However, such a conclusion would be unwarranted. Why?
The study is a test tube experiment. The study does not, however, describe biochemistry or biology, and its relevance to reactions occurring in cells and tissues of the human body is unknown. Many reactions of vitamin C occur in vitro (in the test tube) that will not and cannot occur in vivo (in the living organism). Why? Because the physiological environment of the cell and the body contains thousands of substances that also react with vitamin C and lipid hydroperoxides, “derailing” the chemistry observed in a test tube system.
For example, lipid hydroperoxides don’t just wait around in vivo to bump into a vitamin C molecule, but instead are very rapidly reduced to harmless “alcohols” by a number of enzymes. Thus, the reaction rate of lipid hydroperoxides with these enzymes compared to the reaction rate of the lipid hydroperoxides with vitamin C is of crucial importance. Curiously, the reaction rate of lipid hydroperoxides with vitamin C was not measured in the Science study. From what we know from the study, incubations were done for two hours, an eternity in biochemical terms. Enzymatic reactions as those indicated above to reduce lipid hydroperoxides to harmless alcohols that do not react with vitamin C usually take a fraction of a second, not two hours!
Other studies like this one : “A short overview of vitamin C and selected cells of the immune system” have shown that vitamin C effectively inhibits the formation of lipid hydroperoxides in the first place. Thus, when human plasma is exposed to oxidizing conditions, vitamin C forms the first line of antioxidant defense, and no lipid hydroperoxides are formed. Lipid hydroperoxides begin to form only after vitamin C has been exhausted. Thus, in these experiments lipid hydroperoxides and vitamin C did not co-exist in human plasma, and thus never had the opportunity to react with each other! What’s more, the Science study used a concentration of lipid hydroperoxides of 400 µM, which in biochemical terms is “a ton.” Studies have shown that in human blood, lipid hydroperoxides may exist in concentrations of about 10 – 40 nM, which is 10,000-fold lower than what was used in the Science experiment. Again, this casts serious doubt on the relevance of these results for living organisms.
Vitamin C does not cause cancer and is a critical antioxidant in our defence system.