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Friday 28th October 2016

Antioxidants linked to cancer risk

11th October 2011

Using antioxidants can, in some cases, accelerate the development of breast cancer and increase people's risk of dying, according to a recent US study.


The researchers found that the outcome depended on the vitamin the patients were using, and that multivitamins, due to the fact that they contain moderate doses of nutrients, tended not to have an associated risk.

But using carotenoids seemed to have a particularly high association with early death.

Antioxidants are known to protect cells from wear and tear, and because chemotherapy and radiation both oxidate the body, patients take them to ward off damage.

Breast cancer patients who take antioxidants may have an increased or decreased risk of death or recurrent cancer, depending on which vitamin they use, a new study suggests.

Lead researcher Heather Greenlee, an assistant professor of epidemiology at Columbia University in New York, said that, in her opinion, the paper added to the growing body of literature against using high doses of carotenoids.

She said she believed that people should think twice before taking high doses of vitamin A, beta-carotene, lutein, and other carotenoids.

Other studies have also shown a similar result, that giving beta-carotene to smokers increases lung cancer rates.

For the study, the researchers followed 2,264 women who had breast cancer for five years.

At the beginning of the study, the researchers sent the women questionnaires and asked about their use of antioxidant therapies.

More than 80% of the women had used such therapies within the first two years of being diagnosed with breast cancer.

The researchers found that, after five years had elapsed, women who took vitamins C and E were much better off, though only if those women took the vitamins almost every day.

About 15% of the women who took either vitamin almost daily had a breast cancer recurrence, whereas the recurrence for women who did not take either was about 19%.

However, when it came to any combination of carotenoids, there seemed to be a higher risk of death.

Greenlee said that, since vitamins were different at a chemical level, that made them likely to have different effects on the body.

In the five years since the study began, 18% of the women who used carotenoids six or seven days a week died, whereas less than 7% of the women who did not use any carotenoids also died of breast cancer.

Greenlee said that, although the finding needed to be confirmed by further studies, she believed that antioxidant dietary supplements should not be assumed to all act in a similar fashion, as is a common perception in the general public.

She said that, although there was a healthy user bias in such results, in which women who took dietary supplements tended to have healthier habits than women who did not, such a bias could not explain the higher risk of death associated with carotenoid antioxidants.

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