Use of herbal and other dietary supplements may have impact on cancer risk

Dr. Jessie Satia

Certain herbal and specialty supplements may increase one’s risk of developing lung and colorectal cancers, while others may decrease the risk, according to a new study led by Jessie Satia, PhD, associate professor of epidemiology and nutrition in the University of North Carolina at Chapel Hill’s Gillings School of Global Public Health and School of Medicine and member of the UNC Lineberger Comprehensive Cancer Center.

The research, which examines the use of 11 supplements including glucosamine, chondroitin, fish oil, garlic pills and others, is published in the May issue of Cancer Epidemiology, Biomarkers and Prevention, the leading cancer prevention journal.

As part of the VITAL (Vitamins and Lifestyle) cohort, 77,000 men and women in western Washington state, aged 50 to 76 years, completed in-depth questionnaires about the frequency and duration of their supplement use during the decade prior to interview. They also provided information about their health histories and risk factors. Responses were matched against data from the Surveillance, Epidemiology and End Results (SEER) registry to track rates of lung and colorectal cancers.

Results show that any use of glucosamine or chondroitin over the previous 10 years was associated with significantly lower risk for both cancers. The use of fish oil, melatonin, methylsulfonylmethane (marketed for the treatment of osteoarthritis) or St. John’s wort was associated with a 35 to 65 percent reduced risk of colorectal cancer. In contrast, the use of garlic pills was associated with a significant (35 percent) elevation in the risk of colorectal cancer.

“One reason why glucosamine and chondroitin may have been associated with reduced risk for these cancers is that they are believed to have anti-inflammatory properties,” Satia said. “There is growing evidence that inflammation may initiate or promote the development of both lung and colorectal cancers.” Satia says the findings showing a relationship between fish oil supplements and melatonin and colorectal cancer risk are in agreement with previous studies. 

The surprise may have been the findings about garlic, long extolled for potential health benefits. “The finding of a slightly elevated risk associated with use of garlic pills is somewhat contrary to the previously published studies,” Satia said. “Possible reasons for this discrepancy include the considerable heterogeneity in assessment/measures of garlic intake, types of garlic consumed (e.g., cooked, fresh, extract) and outcome (colorectal cancer, adenoma number and/or size).”

The use of alternative medicines, including non-nutritive dietary supplements, has increased dramatically over the last decade, despite the population’s lack of reliable information about their benefits and risks. Satia and colleagues call for additional studies to examine the effects of herbal and other specialty supplements on the risk of cancers and other diseases.

Co-authors of the study include Alyson Littman, PhD, research assistant professor of epidemiology at the University of Washington at Seattle; Christopher G. Slatore, MD, pulmonary and critical care medicine fellow, University of Washington at Seattle; Joseph A. Galanko, PhD, research assistant professor of medicine, UNC School of Medicine; Emily White, PhD, professor and associate dean of the School of Public Health at the University of Washington and member of the Fred Hutchinson Cancer Research Center.

A study by Satia using the same cohort, published earlier this year in the American Journal of Epidemiology, reported that long-term use of beta carotene, especially by smokers, may increase risk of lung cancer.

An abstract of the current study is available at http://cebp.aacrjournals.org/.

Note: Satia can be reached at (919) 843-3641 or jsatia@unc.edu.

UNC Gillings School of Global Public Health contact: Ramona DuBose, director of communications, or ramona_dubose@unc.edu.