Vitamin C And
Chester J. Zelasko, Ph.D. |
March 16, 2007
One of the most
common questions we get at Better Life involves the use of supplements
during cancer treatment. Patients are told by their doctors that they
shouldn’t use antioxidants because they may make the treatment ineffective.
Patients become concerned about continuing their normal supplements because
they contain antioxidants; they also want to know what else they could do to
help themselves heal.
Let’s be very clear: dietary supplements do not cure cancer. However, they
may help during cancer treatment. This Newsletter will examine the research
on whether vitamin C is beneficial or harmful during cancer treatment.
When Did All This Begin?
"It's possible that taking large amounts of vitamin C could interfere with
the effects of chemotherapy or even radiation therapy." That quote is from
Dr. David Golde, a cancer researcher at Memorial Sloan-Kettering Cancer
Center, and was included in a 1999 press release. Since then, the use of
antioxidants, especially vitamin C, has been discouraged by oncologists and
physicians who treat cancer. The question is why did he make that statement?
Moreover, is it accurate and a cause for concern?
In a series of elegant experiments, Dr. Golde and his colleagues identified
the mechanism by which vitamin C can be transported into cancer cells (1).
While the biochemistry is complex, the essence is that vitamin C is
transported into cells via glucose-transporter mechanisms. Why is that
significant? Because cancer cells appear to have more glucose transporters
than normal cells do, and that allows them to use glucose (sugar) as energy
to grow. If vitamin C is present in high quantities, the same mechanism will
increase the uptake of vitamin C into the cell (2).
The question is why do cancer cells want vitamin C? The theory is that the
cancer will use the vitamin C to protect itself against the body’s normal
defense mechanisms, which are trying to destroy the tumor.
In another series of experiments, Dr. Golde and colleagues demonstrated
While this seems to be overwhelming evidence against using vitamin C during
cancer treatment, there two important caveats:
- Vitamin C will inhibit cancer cell death by neutralizing free
radicals inside cancer cells (3).
- Vitamin C will prevent cancer cell death by hindering the
destruction of cellular DNA in cancer cells (4).
- Vitamin C will inhibit cancer cell death by constraining a specific
pathway known for cell death in blood cells and specific types of cancer
- First, these were all test-tube studies, and no matter how carefully
they were conducted, they have severe limitations for applicability to a
whole organism. The body has many complex mechanisms that may neutralize
the effects in individual cells.
- Second, and maybe even more important, none of the experiments used
radiation or chemotherapy to see what roles vitamin C plays during
cancer treatment. Vitamin C’s effects during treatment may be exactly
the opposite of its effects on untreated cancer cells.
Based on the aforementioned research, Dr. Gabriella M. D’Andrea, also of the
Memorial Sloan-Kettering Cancer Center, published recommendations that
vitamin C and other antioxidants not be used by patients during cancer
treatment (6). The concern is that antioxidants will reduce the efficacy of
the treatment, whether chemotherapy or radiation. However, no additional
data supporting that concern is presented.
The logic is understandable. If vitamin C protects normal cells during
treatment, it stands to reason that it will protect cancer cells and reduce
the effectiveness of treatment. The problem is that there’s no evidence to
back that up in any of these test-tube studies.
Tests on Cancer Patients
On the other hand, there’s evidence in a human trial that supplementation
with antioxidants does not interfere with treatment. In a recent study,
researchers gave high doses of vitamin C, vitamin E, and beta-carotene to
patients undergoing treatment for Stage IIIB and IV lung cancer (7). When
compared to patients who received placebos, there were no differences in
survivability--taking high doses of antioxidants did not increase the death
rate by interfering with chemotherapy. In fact, a closer look at the data
reveals that patients using the antioxidants survived at a higher rate than
those using a placebo, but the results did not achieve statistical
significance. We’ll be watching closely to see if these results are repeated
in other studies; then patients and their doctors can decide whether the
very slim chance that antioxidants will help is worth the effort and expense
of taking them.
Other clinical trials are often cited to demonstrate the lack of benefits of
supplementation during cancer treatment. The lack of benefits is limited by
what questions were asked, and often, the wrong questions are asked.
Obviously, scientists want to know if people will live longer if they use
supplements. That’s a valid question, but not the only one. No studies have
compared how people feel while undergoing treatment when they use
supplements versus when they don’t. Even if there’s no difference in
survival rates, if people feel better and have more energy to carry on their
lives during treatment, that’s a legitimate benefit. But it’s not a hard
endpoint and is rarely considered.
In statistics, there’s an often-ignored conclusion called Reserve Judgment
that’s used when there are not enough data to claim statistical
significance, but when the tested item or procedure doesn’t appear to be
non-significant. When it comes to taking vitamin C alone, it may be in the
area called Reserve Judgment.
How does that help you if you’re facing cancer treatment? Do what your
treatment team recommends. If your doctors read the science and conclude
it’s best to avoid vitamin C, do it. If they read it and say there’s enough
evidence to use it, do so.
But don’t think that there’s nothing you can do when it comes to
supplementing during cancer treatment. Life is about balance, and your
nutritional approach should be balanced as well. Supplements that use
whole-plant concentrates provide the balance of vitamins, minerals, and
phytonutrients that are found in foods; these supplements may help keep your
body strong during treatment when your appetite fades and healthy eating
takes a hit. Supplements that contain green tea, alpha-lipoic acid,
grapeseed extract, and shitake- and reishi-mushroom extracts have the
phytonutrients that research has shown to be beneficial in reducing the risk
of getting cancer. There’s every reason to believe they’re a good
alternative to megadosing with any single vitamin during cancer treatment.
- Golde, DW. Vitamin C and Cancer. Integr Cancer Ther 2003;2:158-9.
- Agus DB, Vera JC, and Golde, DW. Stromal Cell Oxidation: A Mechanism
by Which Tumors Obtain Vitamin C. Cancer Research 59, 4555–4558.
- Guaiquil VH, Vera JC, and Golde, DW. Mechanism of Vitamin C
Inhibition of Cell Death Induced by Oxidative Stress in
Glutathione-depleted HL-60 Cells Aliment Pharmacol Ther.
- Lutsenko EA, Carcamo JM, and David W. Golde. Vitamin C Prevents DNA
Mutation Induced by Oxidative Stress. Journal of Biological Chemistry
- Perez-Cruz I, Carcamo JM, and Golde DW. Vitamin C inhibits
FAS-induced apoptosis in monocytes and U937 cells. Blood.
- Gabriella M. D’Andrea Use of Antioxidants During Chemotherapy and
Radiotherapy Should Be Avoided. CA Cancer J Clin 2005;55;319-321.
- Pathak AK et al. Chemotherapy Alone vs. Chemotherapy Plus High Dose
Multiple Antioxidants in Patients with Advanced Non Small Cell Lung
Cancer. J Amer College Nutr 2005;24 (1):16–21.