The research, published in the journal Cancer Causes Control, claims that supplementation with multivitamins, especially those containing vitamins A, C, E, and folate are linked to lower risks of colon cancer.
“Total intakes of vitamins A, C, and E were associated with 24–30 percent lower risks of colon cancer…,” wrote the researchers, led by Dr. Stephanie Smith-Warner, associate professor of nutritional epidemiology at Harvard Medical School.
“After adjusting for other colon cancer risk factors, the inverse associations for total intakes of vitamins A, C, and E were attenuated slightly, but remained statistically significant,” they added.
The new findings follow a study published last week reporting patients using multivitamins during and after treatment for colon cancer do not reduce the risk of cancer returning or the risk of mortality.
A small number of observational studies have investigated the links between vitamins A, C, and E intake and colon cancer risk – with inconsistent results, report the authors.
The aims of the new research were to evaluate the associations between vitamins A, C, and E and risk of colon cancer, using primary data from 13 previous cohort studies with over 650,000 participants.
Dietary intakes of vitamin A, C, and E were found to be not associated with colon cancer risk. However the researchers reported a strong inverse association for the vitamins when looking at dietary and supplementary multivitamin intake.
Multivitamin use - especially in combination with individual vitamin supplements – was reported to be significantly associated with a reduced colon cancer risk, whilst raised folate intake was also related to a lower risk.
“After adjusting for folate intake, the inverse association between total vitamin A intake and risk of colon cancer …were no longer statistically significant, whereas the inverse associations between total intakes of vitamins C and E and risk of colon cancer … remained statistically significant,” stated the authors.
The authors noted that there are “plausible biologic mechanisms support our results”, suggesting total vitamin C and E intakes may be associated with a decreased risk of colon cancer due to their ability to break “free radical chain reactions”, and act as electron donors to reduce reactive radicals and iron.
However the researchers concluded that the reported inverse associations with vitamin C and E intakes could be also due to the vitamins’ high correlations with folate intake - which has a similar inverse association with colon cancer.
“We cannot rule out the possibility that the apparent protective effects of total vitamin C and E intakes and of multivitamin supplement use against colon cancer were due to their positive correlations with total folate intake or intakes of other vitamins present in multivitamins such as vitamin B6,” wrote the researchers.
“An inverse association with multivitamin use, a major source of folate and other vitamins, deserves further study,” they added.
Source: Cancer Causes Control
Published online ahead of print, doi: 10.1007/s10552-010-9549-y
“Intakes of vitamins A, C, and E and use of multiple vitamin supplements and risk of colon cancer: a pooled analysis of prospective cohort studies”
Authors: Y. Park, D. Spiegelman, D.J. Hunter, D. Albanes, et al