Posted by teejay on April 1, 2007, at 19:16:22
In reply to Re: antioxidants and mortality » Klavot, posted by Larry Hoover on March 28, 2007, at 10:58:36
From this months VRP newsletter.........
http://www.vrp.com/art/2067.asp
JAMA’s Antioxidant Study:
An In-Depth Examination of a Flawed Report
VRP Staff
There’s an old saying in statistics: if you torture the data long enough, statisticians can “prove” almost anything. This means that if you exclude certain studies, lump differing kinds of studies together into the same data pool, set up your own criteria as to what is biased and what is not, and otherwise bend the rules, you can produce a study that says whatever you’d like. And that is exactly what the researchers did in an “anti-antioxidant” study published in February in the Journal of the American Medical Association.1
This paper, a meta-analysis produced by a team of Danish, Italian and Serbian researchers, was designed to assess the effects of the antioxidant supplements vitamin A, beta-carotene, vitamin C, vitamin E and selenium on death rates in healthy people and people suffering from a disease or condition. The researchers began with 815 studies, and after excluding 747 of them came to a startling conclusion that contradicted a wealth of existing scientific evidence: not only were these antioxidants ineffective in reducing mortality, treating people with beta carotene, vitamin A and vitamin E might actually increase mortality!
The media quickly printed alarming headlines that claimed that antioxidants were harmful, without stopping to analyze the study or ask experts in the field about the validity of the results. Yet a careful review of this meta-analysis reveals that it is full of flaws and draws an unwarranted, even misleading, conclusion that’s not based on a full analysis of the facts.
Some of the major problems with the JAMA study:
• The study is a meta-analysis, which involves combining the data from existing studies to create a single, large “pool” of data that is then used for statistical analysis. But a meta-analysis is only as good as the studies used to construct it. The stunningly obvious problem with the JAMA study is the exclusion of a massive amount of positive research. Out of 815 studies, 747 studies (a full 91 percent) were excluded, leaving only 68 studies for the statistical analysis. Some 400 studies were rejected because none of the participants in these studies died. But if you eliminate almost half of the studies specifically because there was no mortality, it is unfair to use the small number of the remaining studies to “prove” that antioxidants are deadly.
• The clinical trials used in the study were too diverse. They involved several different synthetic antioxidants, widely varying dosages, different durations of use and different types of volunteers. For example, one of the studies looked at the effects of 200,000 IU vitamin A over the course of a single day—a huge dose used for a ridiculously short amount of time. Yet other studies used moderate doses of antioxidants over a period of years. In addition, many of the studies examined the effects of antioxidants such as lutein and zinc that were not even one of the five nutrients that the meta-analysis was focusing on. Using the data from this jumble of studies to create some sort of conclusion is like using 20 different brands of bricks to build a house which later falls down, then claiming the failure was entirely due to Brand X.
• Some of the studies included in the meta-analysis were treatment trials using synthetic antioxidants, designed to test whether taking an antioxidant might cure heart disease or another serious illness. Studies based on such a simplistic premise are bound to fail. Yet their results were included, giving the false impression of a strong correlation between antioxidants and risk of death.
Professor Balz Frei, Director of the Linus Pauling Institute at Oregon State University, summed it up thusly: “All the new study really demonstrates is a bias toward identifying studies or research that show harm caused by antioxidants, and selective removal of research that shows benefits.”What the Study Didn’t Say About Antioxidants
A large body of scientific evidence has found that taking antioxidant supplements can indeed reduce the risk of serious disease. One of the classic antioxidant studies, published in the New England Journal of Medicine in 1993, tracked for eight years more than 87,000 female nurses, ages 34 to 59, all of whom were free of diagnosed cancer and heart disease at the beginning of the study.2 During the course of the study there were 437 nonfatal heart attacks and 115 deaths due to coronary disease. Upon analyzing the nutrient consumption of the volunteers during the eight-year period, the researchers found that the risk of suffering a heart attack fell by about a one-third in those who consumed the highest amounts of vitamin E, compared to those who consumed the lowest. A companion study compared the amount of vitamin E consumption by 39,910 American male health professionals and found that those who took at least 100 IU per day for at least two years had about a 33 percent lower risk of developing coronary disease than those who did not take vitamin E supplements.3
During the 14 years since the publication of these studies, many other researchers have found strong associations between consumption of antioxidants and a lower risk of heart disease, cancer and other diseases, as well as overall mortality. And just the presence of elevated levels of antioxidants in the blood appears to reduce the risk of suffering from serious ailments. For example:
• In a Japanese study involving 3,016 adults, high serum levels of antioxidant carotenoids (alpha-carotene, beta-carotene and lycopene) were “significantly associated with low hazard ratios for cardiovascular disease mortality.”4
• A 2005 study published in the American Journal of Clinical Nutrition compared the levels of alpha-carotene, beta-carotene and alpha-tocopherol in elderly Europeans. The results of this prospective study indicated “that high plasma concentrations of carotene are associated both with lower mortality from all causes and with cancer in the elderly.”5
• A case-control study, nestled within the European Prospective Investigation into Cancer and Nutrition (EPIC), found that “higher plasma concentration of some carotenoids, retinol and alpha-tocopherol are associated with a reduced risk” of developing gastric cancer.6
• In 2006, Australian researchers found that selenium offered protection against cancer of the colon and rectum, and that dietary levels of vitamins E and C “were statistically significantly protective for both colon and rectal cancer at all levels of consumption, and for both vitamins there was a dose-response effect of increasing protection, particularly so for colon cancer.”7
This is just a small sampling of the large number of antioxidant studies with positive outcomes that have emanated from research centers around the world. Yet very few of these were included in JAMA’s anti-antioxidant meta-analysis, which “proved” antioxidants are harmful. Is it because the researchers decided in advance what the conclusion would be, then cherry-picked studies that would support their view?
Our understanding of antioxidants is still evolving, and there are still gaps in our knowledge. Researchers are currently comparing the effects of natural and synthetic sources of antioxidants, of antioxidants in their different chemical forms, of single antioxidants versus combinations, and of varying doses. However, it is clear that both high levels of antioxidant consumption and high levels of antioxidants in the blood are associated with better health and increased longevity.
poster:teejay
thread:744072
URL: http://www.dr-bob.org/babble/alter/20070320/msgs/746089.html