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BETA CAROTENE DATA STRONGER FOR LUNG CANCER RISK REDUCTION

This article was originally published in The Tan Sheet

Executive Summary

BETA CAROTENE DATA STRONGER FOR LUNG CANCER RISK REDUCTION than for all cancers, a scientific panel concluded at a Nov. 2 session on beta carotene and cancer convened as part of FDA's Nov. 1-3 public conference on antioxidant nutrients. Asked to rate the existing data for beta carotene and the nutrient's possible effect on cancer on a one-to-10 scale, members of the panel generally agreed that the data supporting the nutrient's effect on lung cancer is in the eight-to-nine range. However, three members of the six-person panel felt that the data on all cancer were much weaker -- in the four-to-five range. Summarizing the panel's comments, Chairperson Diane Birt, PhD, University of Nebraska Medical Center, noted that "we range from four up to eight and nine -- much higher for lung cancer and, I think, much higher if we look at all carotenoids." Much of the debate surrounding beta carotene revolved around whether the data showed that intake of the nutrient had a positive effect on cancer risk or if the data -- primarily serum data -- indicate that low levels of beta carotene simply represent a marker for cancer risk. Panelists also questioned whether the positive data in humans reflect a specific effect of beta carotene or whether the positive evidence is the result of a diet high in fruits and vegetables or possibly some other carotenoid. Panel member Phyllis Bowen, PhD, pointed out that most of the epidemiological data for cancer are based on dietary beta carotene from fruits and vegetables and, she added, "that [data] looks very, very good." However, the serum data for the different cancer locations, "except for lung and maybe upper respiratory and G-I tract," she noted, "doesn't look as good." Nevertheless, based on some of the animal trial data, Bowen suggested that beta carotene "probably" has an independent effect. Acknowledging that some other carotenoids may play an important role, panel members Fred Gey, PhD, University of Basel, Switzerland, and Harinder Garewal, PhD, University of Arizona Cancer Center, both agreed that there is "considerable evidence" that beta carotene has some effect on cancer risk reduction. Other committee members took a more conservative view of the data. Guest speaker Norman Krinsky, PhD, Tufts University, suggested that the available data do not allow a conclusive determination that beta carotene has a specific effect on cancer risk given the potential role of other carotenoids and that positive results were obtained from diet-based studies, which featured diets low in fats and high in fruit and vegetables. In his presentation, Krinsky said the available data indicate that beta carotene has both an antioxidant effect as well as possible synergies with vitamin A. However, he pointed out that the data in humans supported dietary changes but not necessarily beta carotene supplementation. He also suggested that the data are not yet ready for the development of an RDA for beta carotene. Most panel members agreed that sufficient amounts of beta carotene could be obtained from dietary sources and that the emphasis, therefore, should be on dietary intake rather than supplements. Panel member Louise Canfield, PhD, University of Arizona, advised caution "in terms of recommending supplements" given the possibility of inhibiting other carotenoids that could lead to a "dietary imbalance." Two members on a four-person panel that specifically addressed the question of beta carotene and lung cancer on Nov. 2 suggested that supplements may be advisable for smokers and poor absorbers of the nutrient. Thomas Edes, MD, University of Missouri, noted that optimal levels of beta carotene may be difficult to achieve from diet, particularly for long-time smokers who often lose their taste for fruits and vegetables. However, the other two scientists on the panel -- Jin Lee, MD, MD Anderson Cancer Center, and Tammy Bray, PhD, University of Guelph, Canada -- were adamantly opposed to dietary supplement use, even for smokers. Both panelists felt the data supporting supplementation was weak. Bray added that she was concerned about a "magic pill" approach to good health. Both panels strongly agreed that there is a dearth of clinical trial evidence to support beta carotene's effect on cancer. Several panelists suggested tht a clinical trial needs to be done in high-risk cancer patients using, if possible, intermediate end-points.
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