Posts Tagged ‘supplements’

Which study should I believe?

Wednesday, October 26th, 2011

Vitamin E has this chemical structure

I just read the recent (Oct 12, 2011) JAMA article on “Vitamin E and the Risk of Prostate Cancer.” It was a long-term, prospective, randomized study of 33,533 men followed in 427 study sites in the US, Canada and Puerto Rico. The investigators were from major academic centers, Duke, the Cleveland Clinic, Brigham and Woman’s Hospital (e.g., Harvard) and the National Cancer Institute among them.

This was an impressive study of the effects of Vitamin E and/or selenium versus placebo that began in 2001 with the subjects being “relatively healthy men.” Seven years after it began, in September 2008, the independent data and safety monitoring committee decided that the supplements should be stopped as there had been no positive results (reduction in prostate cancer detection) and futility analysis (a statistical tool) said the results were quite likely to be negative (more cases of prostate cancer). I hadn’t heard of that term and found a medical website that discussed a number of reasons for ending a study prior to the intended date. I’ll paste in the URL if you want to read a one-pager on what is called “interim analysis.”

http://www.childrensmercy.org/stats/plan/interim.aspx

In this study, though the researchers stopped giving supplements and published an article (JAMA.2009;301(1):39–51) on the results to date, which showed a higher (but not statistically significant) number of cases of  prostate cancer in the groups receiving Vitamin E, selenium or both, they also continued following the patient group.

Prostatic cancer under the microscope

The later data, though July 5, 2011, was quite impressive. There was a 17% higher incidence of prostate cancer in the group taking Vitamin E. In most scientific studies a p-value of 0.05  is felt to be significant. That translates to a probability of 5% or less that whatever happened did so by chance. If the data calculates to a p- value of 0.01, there’s a 1% chance this was a random occurrence. Here, after ~eleven years the p-value for Vitamin E increasing the chance a man was diagnosed with prostate cancer was 0,008. (I’ll paste in a website that explains more of this stuff if you’re remotely interested).   http://www.childrensmercy.org/stats/definitions/pvalue.htm

Why all the math and statistics?

Well, for starters, a few years back a large study showed the exact opposite, but in a highly selected group: men in Finland who were smokers. Another study, done with physicians as the subjects, showed no effect on the incidence of prostate cancer. A post by a physician harshly criticized the SELECT trial as part of a lengthy defense of supplements, but made sweeping pronouncements without supplying data or references to specific articles.

I read the articles, the blog post and the new study in detail. I know that medical research projects often come to conclusions that, a few years later, are “proven” incorrect. But I think this study was carefully done, had a clear-cut purpose in mind and included a large enough group of subjects that I’m going to believe its conclusions.

Plus I’m certainly not a Finnish smoker.

 

 

Do I need to eat my words?

Wednesday, October 19th, 2011

Different choices for different ages

An old friend forwarded an article on vitamins yesterday, one that I read with special interest. It came from MedPage Today, an online medical news service for healthcare professionals that partners with the University of Pennsylvania School of Medicine to offer physicians continuing medical education credit (CME) for reading articles and then answering a few questions.

The article was titled “Vitamin Studies Spell Confusion for Patients” and extensively quoted Dr. David Katz fromYale’s prevention research center. He is an adjunct Associate Professor at Yale’s School of Medicine and an internationally renowned authority on nutrition. He comments that, based on the recent study I mentioned several posts ago, many clinicians say they’ve written off supplements for good.

Yet 50% of Americans take supplements; many take more than just a multivitamin.

Then Dr. Katz offers some caveats as I did, stating the Iowa study is “merely observational and can’t prove cause and effect.” He still recommends omega-3 fatty acids (AKA “fish oil”) and vitamin D for most of his patients and adds calcium for women and prenatal vitamins and folic acid for pregnant women. otherwise he only uses vitamins when there are deficiencies.

A recent pole of clinicians found that 70% favor annual screening of specific vitamin levels to treat deficiencies. Which vitamins (and minerals) might be measured as part of an annual focused screening examination and whether medical insurance plans would cover such laboratory tests has not been delineated, as best I can find.

But I’m seventy, and articles from 2005 to 2010 in authoritative sources, talk about seniors needing much more B12, having multiple minor, but significant, vitamin deficiencies, and not eating well-balanced, healthy diets, even here in the United States, much less in other spots around the world. I’m lactase deficient and small-boned; do I need a calcium supplement?

clearly the best way to get your vitamins

I agree with Dr. Katz that eating a balanced diet would be a better answer, at least for those who are younger. The concept of “eating your colors,” i.e., having multiple suit and vegetable dishes over the day which contain different phytochemicals as represented by the color of the food itself, makes great sense.

How many Americans do that at present or are likely to do that even if medical figures recommend such?

I regard this as an ongoing discussion. Dr. Katz is certainly correct in saying that vitamins have been shown to treat disease states, but not to prevent chronic disease. The surmise in the article in MedPage seems sound to me: vitamin isolates are less effective on their own and a full blend of antioxidants and phytochemicals (again, best found in those whole fresh fruits and vegetables, may be the key to obtaining maximum benefits.

This discussion is likely to go on and on, so I’ll supply two URLs that may help you, in consultation with your own physician, make choices that are relevant to your nutritional status, age and degree of health.

http://www.uspharmacist.com/content/d/senior%20care/c/21981/

http://www.fda.gov/Food/DietarySupplements/ConsumerInformation/ucm110493.htm