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Don't throw supplements baby out with observational study bathwater, expert urges

By Hank Schultz , 16-Jan-2013
Last updated the 16-Jan-2013 at 16:31 GMT

Another Harvard publication has warned readers that supplements are all style and no substance.  In the January edition of Harvard Women’s Health Watch, the authors downplayed the purported effects of supplements because most of this information has come from observational studies.

In the article, titled, “Dietary Supplements, Do they help or hurt?” the authors stated, Getting our nutrients straight from a pill sounds easy, but supplements don't necessarily deliver on the promise of better health. Some can even be dangerous, especially when taken in larger-than-recommended amounts.”

But while it is true that observational studies have their limitations, it’s unwise to throw the baby out with the bathwater, said Stephen Barnes, PhD, a professor of pharmacology and toxicology at the University of Alabama Birmingham.

“I don’t think an observational study proves anything. The whole point of epidemiology is not to establish cause.  It establishes relationships,” Barnes told NutraIngredients-USA.

“Harvard has made a huge amount of money out of the Women’s Health Study (a long term, observational study) doing exactly that.”

Evidence doesn't match enthusiam

Dr. JoAnn Manson, a professor of medicine at Harvard and chief of preventive medicine at Brigham and Women’s Hospital and principal investigator of a large, ramdomized trial known as VITAL (Vitamin D and Omega-3 Trial)  She was quoted in the article as saying, "Often the enthusiasm for these vitamins and supplements outpaces the evidence. And when the rigorous evidence is available from randomized controlled trials, often the results are at odds with the findings of the observational studies."

“I think all of this has to be put into perspective,” Barnes said. “This sort of thing comes from the drug community and they think they are superior to everyone else.”

“I think it also has to be said that an awful lot of drug trials fail.  The drug side of things has the problem that whatever you take is probably toxic, at least at the dosages that  are therapeutic.  Dietary interventions are different because they don’t come with a toxicity so long as you are using moderate dosages.  So your expectations for that are a little lower,” he said.

Appropriate study design

Barnes has raised the point in industry forums in the past about the inherent difficulty in rigidly applying the double-blind, placebo-controlled drug trial model to study dietary interventions. 

“Drugs are used for the most part for acute treatments.  They have to have a much more defined benefit, and one that might overcome the other variables that would come from patient to patient,” Barnes said.

“Is it fair to put a dietary supplement up against a drug that has been tested for a specific reason?” he asked.

“I don’t think dietary supplements are ineffective, they are just not as effective as the acute phase of a drug that has been designed for a specific purpose, which comes with its own set of hazards,” he said.

The search for an absolute, black-and-white, right-or-wrong answer seems to be part of the times, Barnes said.  Supplements either work, or they don’t, right?

“A sense of proportion is the relevant phrase here.  People tend to be on one side or the other in this country; it’s the whole of politics. You have to stand back and look at it from a more detached standpoint and generally it’s a little clearer,” he said.

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