Vitamin E Supplements May Do More Harm Than Good

Experts say too much of anything 'potentially harmful'

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Many people take vitamin E supplements thinking the antioxidant will help fight lung cancer. A new study suggests that those supplements have exactly the opposite effect in mice.

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Researchers in Sweden gave vitamin E supplements in amounts four to 50 times the U.S. recommended daily intake to mice with early lung cancer. The researchers expected the supplements to slow the tumors’ growth, but instead the tumors multiplied and grew more quickly. Results appear in the journal Science Translational Medicine.

Whether those effects would be the same in humans is not proven, says oncologist Nathan Pennell, MD, PhD.

“The study’s results are useful from a model standpoint, but I wouldn’t use it to argue that patients are in danger,” he says. “We need to be cautious about it.”

But the researchers could be on to something.  A growing body of evidence, including the recent Sweden study, suggests that vitamin supplements may do more harm than good in patients with certain types of cancer.

For example, a groundbreaking 1994 National Cancer Institute study showed an increase in lung cancer among smokers who took supplements of another antioxidant, beta-carotene. Because of that study, doctors now recommend that smokers avoid taking beta-carotene supplements.

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Studies such as the more-recent mouse study in Sweden are important because complementary therapies hold high interest for many people, Dr. Pennell says. But as with many things, moderation is key.

Numerous studies have shown that eating fruits and vegetables rich in antioxidants helps lower the risk of chronic diseases such as cancer. That’s because antioxidants fight free radicals, naturally occurring substances in the body that contribute to chronic diseases such as cancer by damaging cells and genetic material.

But whether antioxidant supplements can affect the development or lessening of chronic disease is uncertain.

“Although vitamins are essential parts of staying healthy, too much of anything is potentially harmful,” Dr. Pennell says. “Your body is not built to take in incredibly high levels of these vitamins.”

The mouse study is valuable in that researchers found that antioxidants appear to decrease the amount of a protein called p53, which aids the body in suppressing in tumors, Dr. Pennell says. If, as the researchers theorize, deficiency of that protein speeds up cancer progression, the study may provide good insight for future research and possibly therapies, Dr. Pennell says.

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“The body’s defense against cancer is to induce cell death,” Dr. Pennell says. “With antioxidants, you could interfere with the process and make the cancer worse.”

Vitamin E supplements also could interfere with therapies such as radiation and chemotherapy, which fight cancer by inhibiting cell division in various ways, including damaging DNA, Dr. Pennell says.

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