EXCESS INTAKE OF VITAMIN E, SELENIUM, OR BETA CAROTENE MAY INCREASE CANCER RATES

 A consensus statement released by the U.S. Preventive Services and the results of a new study both find that there are potential downsides to taking some vitamins and minerals. 

A panel of experts was recently convened to give Americans better guidance on supplementation.  The 16-member panel took an in-depth look at studies conducted over the past 10 years on vitamins and minerals and found  there was no conclusive evidence multivitamin improve health.  The panel also stated healthy Americans should not take vitamin E or beta carotene supplements to help prevent heart disease or cancer and that, for smokers, beta carotene supplements may actually increase the risk of lung cancer.  In two large studies taking beta carotene increased the risk of lung cancer in smokers by 24%.  There is also limited evidence that taking high levels of folate can increase colon cancer rates.

Additionally, a large supplementation trial found men taking selenium or vitamin E supplements can double their risk of prostate cancer.  The study, begun in 2001, was prompted by early research suggesting the supplements might protect against prostate cancer. But, researchers found that taking selenium increased the risk of high-grade cancer by 91% among men with already high selenium levels.  Among men with low selenium levels, taking vitamin E increased the risk of prostate cancer by 63% and the risk of aggressive cancer by 111%.

Men can still take their daily multivitamin without fear, however.  The levels administered in this study significantly exceeded the recommended daily intake and were higher than would be found in most multivitamins.  During the trial, men took 200 mcg of selenium and 400 IU of vitamin E daily, either separately or in combination.  By comparison, the recommended daily intake of selenium for adults is 55 mcg, and for vitamin E it is 22 IU. 

What to do:  If you want to take a multivitamin it is likely doing no harm but it also may be doing no good.  As the study findings reveal, taking large doses of supplements can increase cancer risk.  Certainly, supplements are no substitute for eating a healthy diet, getting regular physical activity, and controlling body weight.  Instead of supplements aim for healthy foods naturally rich in vitamins and minerals.  To get adequate vitamin E and selenium aim for whole grains, nuts, and dark leafy greens.

Adapted from articles available at:

http://www.nlm.nih.gov/medlineplus/news/fullstory_144782.html

http://www.cancer.gov/newscenter/qa/2008/selectqa

Sources: 

Sources: 

Frankel PH, Parker RS, Madsen FC, Whanger PD.  Baseline selenium and prostate cancer risk:  Comments and open questions. Journal of National Cancer Institute. Available at dju060 doi:10.1093/jnci/dju060.

Kristal AR, Darke AK, Morris JS, et al.  Baseline Selenium Status and Effects of Selenium and Vitamin E Supplementation on Prostate Cancer Risk. Journal of National Cancer Institute.  Available at djt456 doi:10.1093/jnci/djt456 first published online February 22, 2014.

U.S. Preventive Services Task Force.  Vitamin, Mineral, and Multivitamin Supplements for the Primary Prevention of Cardiovascular Disease and Cancer.  Annals of Internal Medicine on 25 February 2014.  Available at: http://www.uspreventiveservicestaskforce.org/uspstf14/vitasupp/vitasuppfinalrs.htm#copyright