Beverage studies tend to get sweet results: study
Does milk lower blood pressure? Does juice prevent heart disease? Beverage studies were four to eight times more likely to reach sweet conclusions about health effects when industry was footing the bill, a new report contends.
Its authors claim to have done the first systematic analysis of such studies published from 1999 through 2003 in hundreds of journals around the world.
"We found evidence that's strongly suggestive of bias," said Dr. David Ludwig, an obesity specialist at Children's Hospital Boston who led the work, which was published Monday in the online science journal PLoS Medicine. The consumer advocacy group Center for Science in the Public Interest also participated.
Biased science can affect consumer behaviour, doctor recommendations and even federal regulation of marketing claims for such products, Dr. Ludwig said.
"I don't blame researchers for this problem. I think most are highly ethical and dedicated to science. The problem is that when government underfunds nutrition research, industry money becomes hard to resist," he said.
However, beverage industry folks say the authors have a slant, too.
"This is yet another attack on industry by activists who demonstrate their own biases in their review by looking only at the funding source and not judging the research on its merits," says a statement by Susan Neely, president of the American Beverage Association. "The science is what matters - nothing else."
Public health experts who promote dietary guidelines are biased toward their own advice, said Greg Miller, a nutrition biochemist who heads research for the National Dairy Council. The council requires its funded researchers to publish results in journals that require review by outside scientists and to disclose who pays for their work.
"Everybody brings a point of view to the table, and in the long run, that's probably a good thing," Dr. Miller said.
But the authors say this point of view appears to influence results.
They used Medline, a compendium of scientific literature, to identify 538 studies about soda, milk or juice involving people, not animals. They targeted 206 that made a health claim directly related to the drink being studied - for example, bone fractures related to calcium and milk intake, or immune system benefits from antioxidants in juice.
Of the 206 studies, only 111 gave information on funding: 22 per cent were fully funded by industry and 32 per cent got some industry money.
One group of reviewers analyzed study conclusions and classified them as favourable, neutral or unfavorable to the beverage in question. Another independent group of reviewers determined whether a study would help, harm or have no effect on the finances of the study sponsor.
For example, a negative finding about soda would harm a soda sponsor but could help a dairy producer.
Overall, studies funded entirely by industry were four to eight times more likely to be favourable to their sponsors.
None of the experiments fully funded by industry that tested beverages with a control group found fault with the drinks.
The authors' work was paid for by a grant from the Charles H. Hood Foundation, which finances research on children's issues at Dr. Ludwig's hospital. Co-author Dr. Lenard Lesser also had funding from a fellowship at the Rochester School of Medicine and Dentistry.
The beverage association complained that Dr. Ludwig is on the editorial board of the journal that published his study. However, Dr. Ludwig noted that the board has more than 100 scientists on it, and said his study went through an independent review.