A reader asked an interesting question recently that I thought would make a good post. The question involved the use of antioxidants, either for dogs with cancer or to help prevent cancer.
Lets get an overview to clarify this frequently-muddied picture.
A free radical is a reactive molecule that tends to damage cell parts. When DNA is damaged, this can mean damaged genes. If the genes controlling cell multiplication are harmed, cell growth can get stuck in the “on” position.
When cell growth is stuck “on”, this spells cancer.
Cancer cells are very active doing all this growing. One of the by-products of all this activity in an increased load of free radicals within the cancer cell.
Cancer cells are not good at handling much more free radicals, since they already have more in them than normal cells.
The body is able to quench free radicals with substances called antioxidants. Antioxidants lessen the amount of free radical-induced injury.
A pro-oxidant has the opposite effect. It tends to increase the amount of free radicals.
Since pro-oxidant strategies increase free radicals, it would seem that the way to kill cancer cells is by bombarding them with pro-oxidants. This would lead to more free radicals within cancer cells, and injury to the cancer cells.
The mechanism of many chemotherapy drugs, as well as radiation, in destroying cancer cells is by causing free radical increase within cancer cells. This is the same mechanism in many of the apoptogens discussed in The Dog Cancer Survival Guide.
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Now, healthy cells also suffer when there is free radical excess. It is just they have more of a natural buffer within them than the free-radical filled, madly proliferating cancer cells do.
If the natural body buffers are depleted, this can lead to lack of overall body health in the fight against cancer. That is why maintenance levels of certain antioxidants actually help during the fight against cancer.
We want to preserve overall body health, and minimize side effects of chemo and radiation toxicity. Many chemo and radiation side effects are due to injury of normal body cells by the free radicals caused by these treatments. Here is a good read on the topic.
Maintenance antioxidants help, and this has been evaluated and shown to be accurate, even when these antioxidants were used along with chemotherapy.
However, only some so-called antioxidants should be used in high levels (way above maintenance levels) during cancer treatment with chemotherapy or radiation. At high levels, these substances no longer have antioxidant effects.
Rather, they typically have pro-oxidant effects. Selenium, EGCG, IV vitamin C and others are like this. Some so-called antioxidants at high levels have other ways of killing cancer cells, like inhibiting certain enzymes (curcumin inhibits topoisomerase II).
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If we are relying on conventional care, we don’t want to create abnormally high antioxidant effects in the body, as there could be interference with radiation and chemotherapy. Since these tools work by increasing free radicals, excessive antioxidants may decrease efficacy. Read more here.
It becomes clear that dosages are a central issue with antioxidants. Maintenance levels and high levels do different things.
What about cancer prevention and longevity?
When a dog gets cancer, it is the end result of many damaging events. It likely takes a lifetime of steps, which is why cancer is more typical in older dogs.
It has been said that there are many cancer cells developing in the body daily. True. Developing, but not yet developed. That means they are not actual cancers yet. They are cells on their way to becoming cancer cells.
In the path to true, clinical cancer (the end stage), damaging steps are free radical injury to genes controlling cell growth. There needs to be multiple hits over time in certain locations on the DNA for the damage to finally create a cell growth signal stuck on “on”.
Thus, before true, clinical cancer actually develops, you want antioxidant effects, not pro-oxidant ones, in general.
In contrast, after cancer clinically develops, one could choose pro-oxidants as the anti-cancer weapon.
I hope this helps everyone wondering about vitamins, antixodants, and cancer.
Dr. Demian Dressler is internationally recognized as “the dog cancer vet” because of his innovations in the field of dog cancer management, and the popularity of his blog here at Dog Cancer Blog. The owner of South Shore Veterinary Care, a full-service veterinary hospital in Maui, Hawaii, Dr. Dressler studied Animal Physiology and received a Bachelor of Science degree from the University of California at Davis before earning his Doctorate in Veterinary Medicine from Cornell University. After practicing at Killewald Animal Hospital in Amherst, New York, he returned to his home state, Hawaii, to practice at the East Honolulu Pet Hospital before heading home to Maui to open his own hospital. Dr. Dressler consults both dog lovers and veterinary professionals, and is sought after as a speaker on topics ranging from the links between lifestyle choices and disease, nutrition and cancer, and animal ethics. His television appearances include “Ask the Vet” segments on local news programs. He is the author of The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog’s Life Quality and Longevity. He is a member of the American Veterinary Medical Association, the Hawaii Veterinary Medical Association, the American Association of Avian Veterinarians, the National Animal Supplement Council and CORE (Comparative Orthopedic Research Evaluation). He is also an advisory board member for Pacific Primate Sanctuary.