Researchers examine why antioxidant actually do more harm than good -
For decades, people health conscious worldwide took antioxidant supplements and consumed foods rich in antioxidants, thinking it was one way to good health and long life.
However, clinical trials of antioxidant supplements have repeatedly dashed hopes that consumers take in hoping to reduce their cancer risk. Virtually all of these trials have failed to show a protective effect against cancer. In fact, in several trials antioxidant supplementation has been linked to increased rates of certain cancers. In one trial, smokers taking extra beta carotene were more, not lower, lung cancer rates.
In a brief article in today The New England Journal of Medicine David Tuveson, MD Ph.D., Cold Spring Harbor Laboratory professor and director of research for the Foundation Lustgarten, and Navdeep S. Chandel, Ph.D., of the Feinberg school of medicine Northwestern University, suggest why antioxidant supplements might not be trying to reduce the development of cancer, and why they can do more harm than good.
Their views are based on recent advances in the understanding of the system in our cells that establishes a natural balance between oxidant and antioxidant compounds. These compounds are involved in so-called redox (reduction and oxidation) reactions essential for cell chemistry.
oxidants such as hydrogen peroxide are essential in small quantities and are made intracellularly. There is no doubt that oxidants are toxic in large quantities, and the cells naturally produce their own antioxidants to neutralize them. It seemed logical to many, therefore, to increase the intake of antioxidants to counter the effects of hydrogen peroxide and other "reactive oxygen species," or ROS similar toxic, as they are called by the scientists. Especially since we know that cancer cells produce higher levels of ROS to help feed their abnormal growth.
Drs. Tuveson and Chandel suggested that taking antioxidant pills or eating large amounts of foods rich in antioxidants can not show a beneficial effect against cancer because they act on the critical site in the cells where ROS are produced tumor-promoting - in cellular energy factories called mitochondria. On the contrary, supplements and dietary antioxidants tend to accumulate remote sites scattered in the cell, "leaving the tumor promoting ROS relatively unfazed," the researchers say
The amounts of both ROS and natural antioxidants are more elevated in cancer cells. - paradoxically the higher levels of antioxidants as a natural defense by cancer cells to maintain their higher levels of oxidants in check, so growth can continue Indeed, such Tuveson and. Chandel, treatments that increase the levels of antioxidants into cells may be beneficial, while those that act as antioxidants may also stimulate cancer cells. Interestingly, the radiotherapy kills cancer cells by significantly increasing the levels of . oxidants the same is true of chemotherapeutic drugs. - They kill tumor cells by oxidation
Paradoxically, the authors suggest that "genetic or pharmacological inhibition of antioxidant proteins" - a concept tested successfully in rodent models of lung and pancreatic cancers - may be a useful therapeutic approach in humans. The main challenge, they say, is to identify proteins and antioxidant pathways in cells that are used only by cancer cells and not by healthy cells. Obstruction production of antioxidants in healthy cells will upset the delicate balance on which redox normal cellular function depends.
The authors propose further research on antioxidants track profile in the tumor and the adjacent normal cells, to identify possible therapeutic targets.
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