Most large, clinical trials of vitamin supplements, including some concluding that they are of no value or even are harmful, have a flawed methodology that renders them largely useless in determining the real value of these micronutrients, a new analysis suggests.
Many projects have tried to study nutrients that are naturally available in the human diet in the same way they would study a powerful prescription drug. This leads to conclusions that have little scientific meaning, even less accuracy and often defy a wealth of other evidence, Balz Frei, professor and director of the Linus Pauling Institute at Oregon State University, said in a new review published in the journal Nutrients.
These flawed findings will persist until the approach to studying micronutrients is changed, Frei said. Such changes are needed to provide better, more scientifically valid information to consumers around the world who often have poor diets, do not meet intake recommendations for many vitamins and minerals and might greatly benefit from something as simple as a daily multivitamin/mineral supplement.
What is needed are new methodologies that accurately measure baseline nutrient levels, provide supplements or dietary changes only to subjects who clearly are inadequate or deficient and then study the resulting changes in their health, Frei said. Tests must be done with blood plasma or other measurements to verify that the intervention improved the subjects' micronutrient status along with biomarkers of health.
Other approaches are also needed that better reflect the different ways nutrients behave in cell cultures, lab animals and the human body, he added.
The new analysis specifically looked at problems with the historic study of vitamin C, but scientists say many of the observations are more broadly relevant to a wide range of vitamins, micronutrients and studies.