Jeffrey Blumberg, PhD is the senior scientist in the Antioxidants Research Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.
He said the recent meta analysis was conducted the way many are, and shares the weaknesses of the type. For one thing, the headlines surrounding the publication make it sound like a new finding, when in fact it adds only incrementally to what has already been written, he said.
Null effect on CVD risk not a new finding
The meta-analysis, titled “Supplemental Vitamins and Minerals for CVD Prevention and Treatment,” was published earlier this week in the Journal of the American College of Cardiology. The authors found that in the studies done with the multivitamin ingredients they were looking at, which included most of the letter vitamins as well as some minerals and other nutrients, the ingredients had no effect on lessening CVD risk nor did they improve the overall mortality picture.
“There’s really not much new here. Out of the 179 studies they included, only 15 were published since the last meta analysis was done. Just imagine how big the results of those studies would have had to have been to swamp the earlier results,” Blumberg told NutraIngredients-USA.
Asking the right questions
Blumberg said he did not want to appear overly critical of how the meta-analysis was done as it conformed to standard practices for this type of study. But he did take issue with the basic questions the researchers were asking.
“There are ways of looking at quality of life. You could look at whether the subjects had better physiological function like lower blood pressure or better immune function or cognitive function. Those would be a better questions to ask, rather than looking at hard outcomes like CVD risk or overall mortality,” Blumberg said.
“Take heart disease. If you do a long enough study, maybe the average onset of heart disease in the control group would be five years. In the test group taking the multivitamins, let’s say the average onset was at 10 years. If your study is 15 years long, the same number of people got heart disease so you don't show an overall effect, but you also don’t show that difference in quality of life,” he said.
“And as for overall mortality, whoever said a dietary supplement could prevent you from dying?” Blumberg asked.
Weakness of meta-analyses for nutrition
Blumberg said this type of study is particularly difficult to do when trying to assemble nutrition studies. It’s not like trying to look for a secondary signal in drug studies, which are all conducted to similar standards, are more standardized in terms of subjects and duration and use standard materials.
“They are mixing apples and oranges to say the least. The actual variation in multivitamins can be pretty broad. They say they controlled for this, but I would like to know how they did this when some of the studies themselves don’t provide that level of detail,” Blumberg said.
“And there is no baseline nutritional data for the subjects. There is an assumption that if the study is large enough and randomized well enough that that evens out on both sides, but you can’t say that for all of these 179 studies,” he said.