Antioxidants - found in supplements and fruits and vegetables - may hasten melanoma progression, a new study has found.
The study, published in the journal Science Translational Medicine, was conducted by researchers from Sahlgrenska Academy at the University of Gothenburg in Sweden.
This is not the first time antioxidants have been linked to the acceleration of cancer. In January 2014, researchers from the Sahlgrenska Academy demonstrated how antioxidants quickened lung cancer development in mice. Later, further experiments on human lung cancer cells corroborated the findings.
Antioxidants are widely touted as a way of preventing cancer and are found in many nutritional supplements, as well as in many foods - including fruits and vegetables.
The reason antioxidants are viewed as "healthy" substances is that they interact with and neutralize free radicals - highly reactive chemicals that can harm cells - ultimately preventing them from causing damage. But after the lung cancer studies called the role of antioxidants in cancer progression into question, the medical community began to investigate this topic further.
'Cancer patients should avoid antioxidant supplements'
The researchers, led by Prof. Martin Bergö, note that the role of antioxidants in melanoma cases is particularly important to investigate - not only because melanoma cells are particularly sensitive to free radicals, but also because the cells can be exposed to antioxidants through means other than diet.
- In 2015, around 73,870 new melanomas will be diagnosed
- In the same year, around 9,940 people will die of the disease
- Melanoma is 20 times more common in white people than in black people.
"Skin and suntan lotions sometimes contain beta carotene or vitamin E, both of which could potentially affect malignant melanoma cells in the same way as antioxidants in nutritional supplements," says Prof. Bergö.
After experimenting on cell cultures from patients with malignant melanoma, the researchers found that while antioxidants protect healthy cells from free radicals that can potentially turn them into malignancies, they may also protect a tumor once it has formed.
In fact, they found that antioxidants double the rate of metastasis in malignant melanoma.
"As opposed to the lung cancer studies, the primary melanoma tumor was not affected," explains Prof Bergö.
"But the antioxidant boosted the ability of the tumor cells to metastasize, an even more serious problem because metastasis is the cause of death in the case of melanoma. The primary tumor is not dangerous per se and is usually removed," he says, adding:
"Previous research at Sahlgrenska Academy has indicated that cancer patients are particularly prone to take supplements containing antioxidants. Our current research combined with information from large clinical trials with antioxidants suggests that people who have been recently diagnosed with cancer should avoid such supplements."
To further their research, the team is currently exploring how skin and suntan lotions affect malignant melanoma by testing whether antioxidants applied to melanoma cells in mice speed up cancer progression in the same way as dietary antioxidants.
Prof. Bergö calls for more research on antioxidants and other forms of cancer "if we want to make a fully informed assessment of the role that free radicals and antioxidants play in the process of cancer progression."
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