CRN looks at contradictory evidence on benefits of vitamin E
WASHINGTON The Council for Responsible Nutrition on Tuesday commented regarding a study to be published in the Dec. 5 issue of the Journal of the American Medical Association, noting that it raises confusion whenever new research contradicts earlier research. Specifically, the JAMA study evaluates literature in support of vitamin E supplements benefiting heart health versus a large randomized controlled trial in 2006 that found no link between vitamin E supplementation and a heart health benefit.
“The problem that we have for the scientific community in evaluating the effects of nutrients in people is that everyone—from scientists to journalists to consumers—wants conclusive answers, consequently we’re always looking at what the ‘study du jour’ tells us and trying to make it answer all questions,” stated Andrew Shao, CRN vice president, scientific and regulatory affairs. “But the reality is that science doesn’t always move forward—there is some back and forth—and while research may seem to contradict itself, that should not be interpreted to mean one type of study trumps another, particularly when different studies ask and answer different questions. Seemingly conflicting data can exist side by side, when one understands that not all studies are asking the same questions in the same populations.”
The JAMA review set out to evaluate the change over time in the quantity and content of citations for two highly cited observational studies that found major cardiovascular benefits associated with vitamin E supplementation and to understand how these benefits continue to be defended in literature, despite contradicting evidence from large RCTs. The study authors conclude that there is “an apparent split of stance in the scientific literature.”
Pertaining to vitamin E the researchers found that, despite the large RCTs that received a great deal of media attention, more than half of the articles that cited the observational studies were favorable towards a beneficial effect of supplemental vitamin E. The study authors write, “Even among articles that cited the contradicting HOPE [RCT] trial, rather than the positive epidemiological studies, the majority in 2005 still could not conclude that vitamin E was ineffective.”
“The RCTs with negative results attempted to answer the question, ‘can a supplemental nutrient treat or reverse a disease or a lifetime of unhealthy habits in patients who are also taking prescription medications,” Shao noted, while the observational studies with positive results attempted to answer the question: “If we start with a mostly healthy population generally free of disease, can we identify various diet/nutrient and lifestyle factors that make them more or less prone to disease?”