From time
to time, negative studies on the effect Vitamin C are published. As scientists,
it is our duty to evaluate each and every study carefully. Data and conclusions
are only as good as the study design and execution.
A study published
in the respected journal Science on June 15, 2001 showed that Vitamin C
can potentially damage DNA. The following is a full analysis of this report
from Linus Pauling Institute.
Does
Vitamin C Cause Cancer -
or Here We Go Again!
A study in the June 15, 2001,
issue of the journal Science shows that lipid hydroperoxides (rancid
fat molecules) can react with Vitamin C to form products that could potentially
harm DNA, although the reaction of these products with DNA was not demonstrated
in the study. Hence, 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. The study is a test
tube experiment, showing some intriguing chemistry of Vitamin C. 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!
In our own studies, we 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.
What
have we learned from the Science study? Some intriguing in vitro
chemistry of Vitamin C. The physiological relevance of these
results has yet to be demonstrated. To conclude from this study that Vitamin
C causes cancer would be as preposterous as to say that we have found a
cure for cancer based on a simple test tube experiment. In fact, many
animal studies and cell culture experiments have demonstrated anticancer
effects of Vitamin C, and the vitamin has been used therapeutically in human
cancer patients with some apparent benefit.
What’s
more, although Vitamin C supplements are often singled out as potential
troublemakers, the body does not distinguish between dietary Vitamin C and
supplemental Vitamin C it’s all the same substance. Thus, if
Vitamin C indeed causes cancer, the advice would be not only to stop taking
supplements, but also to stop eating Vitamin C-rich fruits and vegetables
an absurd recommendation! We know that Vitamin C-rich foods lower
the risk of cancer, heart disease, stroke and other diseases, so the more
fruits and vegetables you eat, the better. And
if you choose to take Vitamin C supplements, stick to it, as the evidence
indicates that you will do yourself a lot of good, and certainly no harm!
I hope you have enjoyed reading this
article. If you have areas you don’t understand, or if you have a specific health concern, feel free to write
to me by clicking here.
About The Author
Michael Lam, M.D., M.P.H., A.B.A.A.M. is a specialist in Preventive and Anti-Aging Medicine. He received his Bachelor of Science degree from Oregon State University, and his Doctor of Medicine degree from Loma Linda University School of Medicine, California. He also holds a Masters of Public Health degree and is Board Certification in Anti-aging Medicine by the American Board of Anti-Aging Medicine. He has authored numerous articles and the following books: The Five Proven Secrets to Longevity, How to Stay Young and Live Longer, Estrogen Dominance - Hormonal Imbalance of the 21st Century, and Beating Cancer with Natural Medicine.
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What’s
more, although Vitamin C supplements are often singled out as potential
troublemakers, the body does not distinguish between dietary Vitamin C and
supplemental Vitamin C it’s all the same substance. Thus, if
Vitamin C indeed causes cancer, the advice would be not only to stop taking
supplements, but also to stop eating Vitamin C-rich fruits and vegetables
an absurd recommendation! We know that Vitamin C-rich foods lower
the risk of cancer, heart disease, stroke and other diseases, so the more
fruits and vegetables you eat, the better. And
if you choose to take Vitamin C supplements, stick to it, as the evidence
indicates that you will do yourself a lot of good, and certainly no harm!
