Part 1 of 2
Up to two-thirds of adults use supplements on a regular basis  despite the fact that many authorities say they should not:
"Vitamins are correlated with an increased risk of diseases such as cancer... stop taking vitamins."  Dr. David Agus does a good job summing up the conventional stance on supplements in a recent Forbes interview. Here is a related quote from another article expressing the same sentiment: "The only thing that taking vitamin supplements could do for you was to produce expensive pee ... If you eat a well-rounded diet, you don't need vitamin supplementation." 
Do vitamins create little more than expensive urine?
In this first installment, I'll discuss some of the latest studies that were done to see if supplements improve health. In the next installment, I'll discuss considerations that will help you make an informed decision based on your personal needs.
Over the last few years, the largest studies on multivitamins/multiminerals evaluated how they affected risks for heart disease, cancer and cataracts.
One study gathered data from the National Health and Nutrition Examination Survey II, conducted between 1988 and 1994. The survey polled 8,678 adults that were over 40-years-old. At this point, 45 percent of the participants had used supplements in the last 30 days. The supplements used the most included multivitamin/multiminerals and multivitamins.
In this study, a group of women took multivitamins for over three years. They had a 35 percent reduction in heart disease which lasted as many as 18 years. 
- Body mass index
- Alcohol use
- Aspirin use
- Cholesterol levels
- Blood pressure
- Blood sugar levels
Next to heart disease, the largest threat we face is cancer. One of the largest studies ever done to find the causes of breast cancer was the Women's Health Initiative Study (WHI). It tracked 161,608 women, ages 50-79, for five years. 
The study tracked use of multivitamins, as well as single-ingredient vitamins, including calcium, zinc and vitamin D. Tragically, 7,728 women developed breast cancer during the study, and 518 died from it. When comparing deaths of those who took multivitamins as opposed to those who did not, the evidence showed those taking multivitamins were 30 percent less likely to die. In concrete terms, this means had all women been taking multivitamins, 155 more would have survived breast cancer.
We've seen similar results in men with prostate cancer. A large study of 14,641 male physicians were tracked for 14 years to see how the use of multivitamins influenced their risk of prostate cancer. This study included a placebo group who took pills that looked like multivitamins but contained no active nutrients. The men taking real multivitamins were 8 percent less likely to develop prostate cancer than those taking a placebo.
The same group of men was also monitored for their risk of developing cataracts. The multivitamins protected 127 from having their vision jeopardized by cataracts.
Given these studies, it appears that vitamins can help reduce deaths from cancer and heart disease and reduce the incidence of cataracts.
I find this evidence compelling enough to invest in my health. Having said that, there are several considerations you should make regarding your age, gender and health that can guide your decisions to ensure the best benefits. These will be the focus of the next article.
Mike Stobbe, "Vitamins: How Many Americans Use Them?" The Huffington Post, June 13, 2012, accessed July 23, 2015, http://www.huffingtonpost.com/2011/04/13/vitamin-use_n_848777.html
2 Robert Lenzner, "Dr. David Agus Wants All His Billionaire Patients To Live To Be 100," Forbes Investing Digest, January 12, 2014, accessed July 23, 2015, http://www.forbes.com/sites/robertlenzner/2014/01/12/dr-david-agus-wants-all-his-billionaire-patients-to-live-to-be-100/
3 Orac, December 19, 2013, "Supplements: Flushing your money down the toilet in expensive urine," Science Blogs, accessed July 23, 2015, http://scienceblogs.com/insolence/2013/12/19/supplements-flushing-your-money-down-the-toilet-in-expensive-urine/
4 Regan L Bailey, Tala H Fakhouri, Yikyung Park, Johanna T Dwyer, Paul R Thomas, Jaime J Gahche, Paige E Miller, Kevin W Dodd, Christopher T Sempos and David M Murray, "Multivitamin-Mineral Use Is Associated with Reduced Risk of Cardiovascular Disease Mortality among Women in the United States," The Journal of Nutrition, accessed July 23, 2015, doi: 10.3945/jn.114.20474
5 Roni Caryn Rabin, May 5, 2014 (3:54 p.m.), "A New Women's Issue: Statins," Well Blog, accessed July 23, 2015, http://well.blogs.nytimes.com/2014/05/05/a-new-womens-issue-statins/
6 Prof Paul M Ridker, MD, Aruna Pradhan, MD, Jean G MacFadyen, BA, Prof Peter Libby, MD, Prof Robert J Glynn, ScD, "Cardiovascular benefits and diabetes risks of statin therapy in primary prevention: an analysis from the JUPITER trial," The Lancet Journal, 380 (9841): 565-71, accessed July 23, 2015, http://dx.doi.org/10.1016/S0140-6736(12)61190-8.
7 S, Wassertheil-Smoler, A.P. McGinn, N. Budrys, R. Chlebowski, G. Y Ho, K.C. Johnson, D.S. Lan, W. Li, M. L. Neuhouser, J. Saquib, J. M. Shikany, Y. Song and C. Thomson, "Multivitamin and mineral use and breast cancer mortality in older women with invasive breast cancer in the women's health initiative," U S National Library of Medicine National Institutes of Health, accessed July 23, 2015, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3902175/