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Type of vitamin E may be key to cancer prevention
Source: (cancerfacts.com)
Thursday, December 16, 2004
OAKLAND, Calif. – Dec. 16, 2004 – A form of vitamin E not found in most manufactured nutritional supplements but is plentiful in many nuts and seeds might halt the growth of prostate and lung cancer cells, according to a new study.
A research team led by Dr. Qing Jiang (pronounced "ching zhang") of Purdue University found that gamma-tocopherol, which occurs naturally in walnuts, pecans, sesame seeds, and in corn and sesame oils, slows the production of lab-cultured human prostate and lung cancer cells.
This gamma-tocopherol form of the vitamin interrupts the production of certain fatty molecules called sphingolipids, important components of cell membranes. However, this form of the vitamin leaves healthy human prostate cells unaffected, which could give it value as an anticancer agent.
"This is the first time gamma-tocopherol has been shown to induce death in lab-grown human cancer cells while leaving healthy cells alone," said Jiang in a news release. "This could be wonderful news for cancer patients if the effect can be reproduced in animal models. But because most nutritional supplements contain only alpha-tocopherol, a different form of vitamin E that does not have these anticancer properties, it may be better to supplement the diet with mixed forms of vitamin E. The study shows that the anticancer effect is enhanced when mixed forms are used."
Jiang's research, which appears in the current online edition of the scientific journal Proceedings of the National Academy of Sciences, may change the focus of vitamin E research.
Scientists early on found that alpha-tocopherol, one of eight known forms of vitamin E, produced the most beneficial effects on laboratory animals fed diets deficient in vitamin E, and also is the major form found in body tissues. For these reasons, it has been nearly the only form of the vitamin to be included in most manufactured nutritional supplements.
"Since then, alpha-tocopherol has justifiably earned a good reputation as an antioxidant, which helps to fight against damage caused by unwanted free radicals," Jiang said. "But its familiarity has perhaps attracted research away from the other seven forms of vitamin E, and since gamma-tocopherol is the vitamin's most commonly occurring natural form in the American diet, I grew interested in it a few years ago."
In 2000 another study by Jiang and colleagues found that gamma-tocopherol inhibits inflammation, which had already been implicated in cancer development. They theorized that it might retard the progress of cancer and cardiovascular disease, and to test their hypothesis they exposed cultures of cancerous prostate and lung cells to the vitamin. Normal prostate epithelial cells were used as a control group.
"We discovered that as we increased the quantity of gamma-tocopherol, the cancer cells grew more slowly," Jiang said. "But the normal prostate cells were not affected and grew normally. This could indicate that the vitamin could be used to target lung and prostate cancer cells without the damaging side effects of chemotherapy."
The study also revealed that gamma-tocopherol caused cell death by interrupting sphingolipid synthesis.
"This is also a novel discovery," Jiang said. "Although there have been prior indications that some form of vitamin E may cause cell death in some mouse cell lines, we are the first to provide a mechanism for such an effect."
Gamma-tocopherol, though rarely available in vitamin pills, is nevertheless found in abundance in many nuts and seeds including walnuts, pecans and sesame seed. Cooking oils such as corn and sesame oil also provide a rich source of gamma-tocopherol.
Though Jiang said she would be cautious about using food sources to slow prostate or lung cancer's progress in humans, she said that high-risk groups such as older men could benefit from supplementation - if carried out with prudence.
"Foods rich in gamma-tocopherol are also rich in fats, and some products bring other hazards as well," she said. "Corn oil, for example, is rich in linolic acid, which has been shown to promote certain types of cancer in some studies. But sesame seeds and pecans seem to be good all-around choices."
Jiang said the next step for her research team would be testing the effect of gamma-tocopherol and mixed forms of vitamin E on animal cancers.
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