No benefits from vitamin supplements in protection against gastro-intestinal cancer

September 30, 2004

This release is also available in German.

A systematic review and meta-analysis (pooled analysis) of previously published randomised trials in this week's issue of THE LANCET provides strong evidence that antioxidant supplements (such as vitamin supplements) are not effective in protecting against gastro-intestinal cancer. Some combinations of supplements may slightly increase gastro-intestinal cancer risk, whereas selenium may be associated with a risk reduction.

The human diet is a complex mix of oxidants and antioxidants. Excess oxidants can cause cancer by inducing gene mutations. Goran Bjelakovic (University of Niss, Serbia and Montenegro) and colleagues from The Cochrane Hepato-Biliary Group reviewed all randomised trials comparing antioxidant supplements with placebo for prevention of gastrointestinal cancers.

The investigators identified 14 randomised trials (totalling over 170,000 participants). Overall, the results did not show any protective effect of supplementation with b-carotene, vitamins A, C, E, and selenium (alone or in combination) compared with placebo on oesophageal, gastric, colorectal, pancreatic, and liver cancer incidences. In half the trials (categorised as high quality), there was a small but statistically significant increase (6% relative risk value) in mortality among people taking antioxidants compared with placebo; the results also showed that two combinations of supplements were associated with increased mortality risk: b-carotene and vitamin A (30% increase in relative risk), and the combination of b-carotene and vitamin E (10% increase in relative risk). Four of the trials suggested that selenium was associated with a reduction in gastro-intestinal cancer risk, but this may be due to bias.

Dr Bjelakovic comments: "We could not find evidence that antioxidant supplements can prevent gastrointestinal cancers; on the contrary, they seem to increase overall mortality. The potential preventive effect of selenium should be studied in adequate randomised trials".

In an accompanying commentary (p 1193), David Forman (University of Leeds, UK) and Douglas Altman (Cancer Research UK) comment: "Somewhat chillingly, Bjelakovic and colleagues also estimate that, despite the small size of the relative risk, if their findings are correct, 9000 in every million users of such supplements will die prematurely as a result. The prospect that vitamin pills may not only do no good but also kill their consumers is a scary speculation given the vast quantities that are used in certain communities". However, they conclude that the findings of the study should only be viewed as preliminary: "The mortality analysis in Bjelakovic and colleagues' review is work in progress, and does not offer convincing proof of hazard. In the event that a hazard is established from a complete review, these researchers will need to identify which specific interventions are associated with any risk. It is unlikely that all supplements will exert a similar effect and it will be vital to establish the safety profile for those with demonstrated benefits."

* In the Heart Protection Study (Lancet 2002; 360: 23-33), antioxidant vitamin supplements were assessed among people at high risk of vascular disease. Vitamin supplementation did not produce any significant reductions in the five-year risk of heart attack, stroke, cancer, or other major outcomes.
-end-
Contact: Dr Goran Bjelakovic, Department of Internal Medicine, Gastroenterology & Hepatology, Medical Faculty, University of Nis, Brace Taskovica 81 18000 Nis, Serbia & Montenegro; T) 381-1853-2381; goranb@junis.ni.ac.yu

Professor David Forman, Centre of Epidemiology and Biostatistics, University of Leeds, Leeds, UK; d.forman@leeds.ac.uk

Lancet

Related Cancer Articles from Brightsurf:

New blood cancer treatment works by selectively interfering with cancer cell signalling
University of Alberta scientists have identified the mechanism of action behind a new type of precision cancer drug for blood cancers that is set for human trials, according to research published in Nature Communications.

UCI researchers uncover cancer cell vulnerabilities; may lead to better cancer therapies
A new University of California, Irvine-led study reveals a protein responsible for genetic changes resulting in a variety of cancers, may also be the key to more effective, targeted cancer therapy.

Breast cancer treatment costs highest among young women with metastic cancer
In a fight for their lives, young women, age 18-44, spend double the amount of older women to survive metastatic breast cancer, according to a large statewide study by the University of North Carolina at Chapel Hill.

Cancer mortality continues steady decline, driven by progress against lung cancer
The cancer death rate declined by 29% from 1991 to 2017, including a 2.2% drop from 2016 to 2017, the largest single-year drop in cancer mortality ever reported.

Stress in cervical cancer patients associated with higher risk of cancer-specific mortality
Psychological stress was associated with a higher risk of cancer-specific mortality in women diagnosed with cervical cancer.

Cancer-sniffing dogs 97% accurate in identifying lung cancer, according to study in JAOA
The next step will be to further fractionate the samples based on chemical and physical properties, presenting them back to the dogs until the specific biomarkers for each cancer are identified.

Moffitt Cancer Center researchers identify one way T cell function may fail in cancer
Moffitt Cancer Center researchers have discovered a mechanism by which one type of immune cell, CD8+ T cells, can become dysfunctional, impeding its ability to seek and kill cancer cells.

More cancer survivors, fewer cancer specialists point to challenge in meeting care needs
An aging population, a growing number of cancer survivors, and a projected shortage of cancer care providers will result in a challenge in delivering the care for cancer survivors in the United States if systemic changes are not made.

New cancer vaccine platform a potential tool for efficacious targeted cancer therapy
Researchers at the University of Helsinki have discovered a solution in the form of a cancer vaccine platform for improving the efficacy of oncolytic viruses used in cancer treatment.

American Cancer Society outlines blueprint for cancer control in the 21st century
The American Cancer Society is outlining its vision for cancer control in the decades ahead in a series of articles that forms the basis of a national cancer control plan.

Read More: Cancer News and Cancer Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.