Antioxidants may accelerate the growth of early cancers or pre-cancerous lesions in some high-risk patients, according to a new study.
Antioxidants, found in many foods and supplements, are chemical compounds that delay cell damage caused by reactive oxygen species. Vitamins A, C and E can all act as antioxidants. The role of antioxidants in cancer has been controversial, with some studies and scientists suggesting they may help prevent or fight cancer and others saying they may worsen the problem.
In the new study, researchers tested the effects of vitamin E and an antioxidant drug called acetylcysteine on lung cancer in mice and in human cells. The doses of vitamin E were about the same as normal daily dietary doses.
Mice with early-stage lung cancer who received the antioxidants experienced accelerated tumor growth. The tumors also became more invasive and killed the mice twice as fast.
Researchers believe that the antioxidants promote cancer growth by decreasing a protein called p53, which is normally involved in suppressing tumors. The antioxidants reduce the action of reactive oxygen species in tumor cells, which decreases p53 activity and allows the tumor’s DNA to remain intact. Consequently, the tumor can grow more efficiently.
If these results can be replicated by other studies, people who are at increased risk of carrying small, undiagnosed tumors – such as smokers – may want to avoid taking extra antioxidants, the researchers said. Further study is required to determine whether these results apply to other types of cancer apart from lung cancer and if antioxidants can help prevent cancer in healthy people.