Contrary to studies that have suggested that antioxidants have no, or even negative, effect on mortality, new analysis reveals that vitamin A and E may, in fact, reduce the risk. The research is published in Cancer Epidemiology, Biomarkers and Prevention, a publication of the American Association for Cancer Research.
Researchers examined more than 14 years of data from 16,008 participants in the Third National Health and Nutrition Examination Survey. The observed a “dose-response decrease in cancer and overall mortality risks with higher vitamin C levels,” according to the abstract. They found both vitamin A and E had U-shaped associations with all-cause mortality. Cancer mortality risks decreased with beta carotene and selenium.
Observational studies have suggested that antioxidant nutrients may reduce cancer and overall mortality risks. However, most randomized trials failed to deliver the goods. Examining non-linear associations between antioxidant levels and health outcomes may explain these discrepant findings. This new data suggest the possible use of novel intervention studies where doses of these agents are individualized. The researchers conclude: “Antioxidant supplement use should be studied in the context of overall mortality and other competing mortality risks.”
In 2007, a review of research carried out by Danish scientists questioning the effectiveness of a range of antioxidants — and even suggesting vitamins A, E, and beta-carotene may increase mortality rates — excited mainstream media while exasperating the supplements industry. Major news outlets all over the world including the BBC, Asian news outlets and many American newspapers ran with predictable headlines such as "Antioxidants don't work" or even more sensationally: "Antioxidants can kill you," while the industry stepped in en masse to defend antioxidants against what it describes as the review's inappropriate terms. A meta-study published in 2004 on vitamin E provoked a similar slew of sensational headlines and industry response.
The industry's criticism revolved around the fact the review included many studies where already diseased subjects were the focus — an area where antioxidant consumption has demonstrated little effect. Criticizing antioxidants for failing to cure disease was preposterous, the industry said.