Most Vitamin Supplement Studies Flawed, Researcher Says
December 31, 2013

Most Vitamin Supplement Studies Flawed, Researcher Says

redOrbit Staff & Wire Reports – Your Universe Online

A majority of large, clinical trials of vitamin supplements, including some that have found supplements harmful, are based on flawed approaches to study design, according to a recent analysis published in the journal Nutrients.

Such faulty methodologies render these clinical studies fundamentally useless in determining the true value of micronutrients, the scientists reported.

Balz Frei, professor and director of the Linus Pauling Institute (LPI) at Oregon State University, said many studies attempt to examine naturally available nutrients the same way they would a powerful prescription drug, leading to conclusions that offer “little scientific meaning, even less accuracy” and that “often defy a wealth of other evidence.”

These flawed findings will persist until the approach to studying micronutrients is changed, he said.

New approaches are needed to provide more scientifically valid information to consumers who may have poor diets that fail to meet the recommended amounts of vitamins and minerals. These are people who may greatly benefit from something as simple as a daily multivitamin/mineral supplement, Frei said.

In the current analysis, Frei and Alexander Michels, an LPI research associate and lead author of the report, examined a number of recent studies linking vitamin C and other micronutrients to adverse health conditions.

They found that most of the studies involved healthy test subjects who had good diets, and who engaged in a sufficient amount of exercise each day.

Since vitamin or mineral supplements, or an improved diet, will mainly benefit people who are inadequate or deficient to begin with, these studies are flawed, the researchers said.  Furthermore, most modern clinical studies do not conduct baseline analysis to identify nutritional inadequacies, and do not assess whether supplements have resolved those shortfalls.  As a result, any clinical conclusion made with such methodology is pretty much useless, they said.

“One of the obvious problems is that most large, clinical studies of vitamins have been done with groups such as doctors and nurses who are educated, informed, able to afford healthy food and routinely have better dietary standards than the public as a whole,” said Frei, an international expert on vitamin C and antioxidants.

The researchers said better study methodologies are needed that accurately measure baseline nutrient levels, provide supplements or dietary changes only to subjects whose diets are clearly inadequate or deficient, and then study the resulting changes in participants’ health.

Frei and Michels also recommend that clinical trials be conducted with blood plasma or other measurements to verify that the intervention improved the subjects’ micronutrient status and biomarkers of health.

“More than 90 percent of US adults don’t get the required amounts of vitamins D and E for basic health,” Frei noted.

“More than 40 percent don’t get enough vitamin C, and half aren’t getting enough vitamin A, calcium and magnesium. Smokers, the elderly, people who are obese, ill or injured often have elevated needs for vitamins and minerals.”

New study approaches are also needed that better reflect the different ways in which nutrients behave in cell cultures, lab animals and the human body, the researchers said.

Many scientists who study these topics are unaware of how nutrients behave differently in a cell culture or lab animal, compared to the human body, something that raises unique challenges with vitamin C research in particular.

"In cell culture experiments that are commonly done in a high oxygen environment, vitamin C is unstable and can actually appear harmful," said Michels.

“And almost every animal in the world, unlike humans, is able to synthesize its own vitamin C and doesn't need to obtain it in the diet. That makes it difficult to do any lab animal tests with this vitamin that are relevant to humans."

Frei noted that despite the shortcomings of many studies of vitamins, which tend to significantly understate the value of supplements, the largest and longest clinical trial to date of multivitamin/mineral supplements found a total reduction of cancer and cataract incidence in male physicians over the age of 50.  That study suggested that up to 130,000 cases of cancer could be prevented each year if every US adult took supplements.

“The cancer reduction would be in addition to providing good basic health by supporting normal function of the body, metabolism and growth,” he added.

“If there’s any drug out there that can do all this, it would be considered unethical to withhold it from the general public. But that’s basically the same as recommending against multivitamin/mineral supplements.”

“It’s fine to tell people to eat better, but it’s foolish to suggest that a multivitamin which costs a nickel a day is a bad idea.”