Jillian L Capodice, LAc reviews the AARP diet and health study regarding multivitamin use and the risk of prostate cancer.
Lawson et al recently reported the results of a recent study of 295,344 men on the relationship between multivitamin use and cancer. This large study concluded that general multivitamin use is not associated with localized prostate cancer but a possibility that men taking high doses of supplements may have increased risk of advanced and fatal prostate cancer.1 However as in any large, observational trial, these results may be open to various forms of interpretation.
Currently, the debate surrounding antioxidant, vitamin and mineral supplementation and cancer chemoprevention is still contentious. Many of the vitamins/antioxidants under scrutiny include vitamin A, beta-carotene, vitamin C, vitamin D, vitamin E, calcium and selenium have known and demonstrated antioxidant potential and are present in the diet in many forms and in various foods. Epidemiological studies were among the first that linked associations between world consumption of fruits and vegetables and cancer risk.2 In the United States, it has also been recommended that a diet high in fruits, vegetables and fiber may have multiple health benefits including reduced risks of cancer, cardiovascular disease and obesity 3 4 5 . Epidemiological studies have also ascertained differences in disease outcome due to multivitamin supplementation. Some of these important studies demonstrate that certain antioxidants act to prevent oxidative damage in some but not all patients such as in the ATBC trial that showed that beta-carotene and vitamin E supplementation decreased prostate cancer but increased risk of lung cancer in male smokers.6
Multiple systematic reviews have also assessed the potential benefit of antioxidants in various patient populations. However the interpretation and translation to clinical practice of these various reviews and the study by Lawson et al are important. In the critique of the study by Lawson et al, the general period of multivitamin supplementation was unknown. Second, questions were not asked on the type, brand or molecular form of each dietary supplement; an important example of the necessity of this information is vitamin E, a supplement readily available in multiple forms but which certain molecules of this tocopherol/tocotrienol, may have different health benefits.7 Third, the nutritional value of nutrients within foods versus those supplemented as well as the dietary versus pharmacologic intake of nutrients is another factor that is important to consider especially based on the proposed altered microenvironments of daily health versus a cancer microenvironment.7 8 Fourth, prostate cancer detection bias (of which the authors duly note) is important when considering observational trials and disease outcomes.1 Finally, statistical arguments are important factors. Strengths of this study include a large observational sample and multiple subgroup analyses of which the authors note potential changes based on chance. Weaknesses include lack of additional multivariate assessments and other stratification comparisons.
In conclusion, the importance of this study underscores a common number of issues regarding diet, nutrition and supplementation such as how many fruits and vegetables are necessary in each one of our diets, what differences may exist between various multivitamins and antioxidants in a healthy state and within certain disease conditions, and finally are there different mechanisms of action of these agents if taken in various forms or within varying microenvironments. While these questions are hardly exhaustive of the concerns regarding nutrition and supplementation, results of ongoing clinical trials such as the SELECT study (vitamin E and selenium supplementation for prostate cancer chemoprevention) will be important in extending our knowledge about vitamins and antioxidants.9 So at this point, what is safe to tell our patients as all generalizations about the effect of antioxidants and supplements in health subjects need to be determined for specifics? An integrative practitioner should be aware of these studies, current guidelines on diet nutrition and in the case of dietary supplements and nutrition, most importantly, advising patients to select the most natural forms of all foods and supplements as possible.
1. Lawson et al. Multivitamin use and risk of prostate cancer in the National Institutes of Health-AARP Diet and Health Study. JNCI. 99;754-64, 2007.
2. Block F et al. Collection of dietary-supplement data and implications for analysis. Am J Clin Nutr, 59(Suppl):23S-9S, 1994.
3. Drewnowski A. The real contribution of added sugars and fats to obesity. Epidemiol Rev. 2007;29:160-71. Epub 2007 Jun 24.
4. Veerman JL et al. Using epidemiological models to estimate the health effects of diet behaviour change: the example of tailored fruit and vegetable promotion. Public Health Nutr. 2006 Jun;9(4):415-20.
5. Kennedy ET. Evidence for nutritional benefits in prolonging wellness. Am J Clin Nutr. 2006 Feb;83(2):410S-414S.
6. Heinomen OP et al. Prostate cancer and supplementation with alpha-tocopherol and beta-carotene incidence and mortality in a controlled trial. JNCI. 90:440-6, 1998.
7. Sen CK et al. Tocotrienols: the emerging face of natural vitamin E.Vitam Horm. 2007;76:203-61.
8. Hord NG et al. Context is everything: Mining the normal and preneoplastic microenvironment for insights into the diet and cancer risk conundrum. Mol Nutr Food Res. 2007 Jan;51(1):100-6.
9. Lippma SA et al. Designing the Selenium and Vitamin E Cancer Prevention Trial (SELECT). J Natl Cancer Inst. 97(2):94-102, 2005.