Many clinical trials appear to have a flawed methodology

January 8, 2014

According to a new U.S. study, many large, clinical trials investigating vitamin efficacy may be using a biased methodology which is useless in determining the real value of these micronutrients.

The study analyzed the methodology of large, clinical trials evaluating the efficacy and safety of vitamin supplements (1). The analysis showed that many randomized controlled trials, including some that have concluded that micronutrient supplementation is of no value or even harmful, are methodologically flawed because they have tried to study nutrients that are naturally available in the human diet in the same way as highly effective drugs. According to the researchers, this leads to conclusions that have little scientific meaning, even less accuracy and often defy a wealth of other evidence. A new approach to the study of micronutrients must be found in order to avoid the reoccurrence of such flawed findings. New methodologies are needed that accurately measure baseline nutrient levels and provide supplements or dietary changes only to those subjects who clearly are suffering from deficiency. The resulting changes in their health should then be studied and tests must be done with blood plasma or other measurements to verify that the inter- vention improved the subjects’ micronutrient status along with other biomarkers of health. Further approa- ches are also needed that better reflect the different ways in which nutrients behave in cell cultures, lab animals and the human body.

The researchers commented that such changes are needed to provide better, more scientifically valid infor- mation to consumers around the world. A large number of people suffer from poor diets and do not meet intake recommendations for many vitamins and minerals (2–5). In the U.S., for example, more than 90 per- cent of adults do not get the required amounts of vitamins D and E for basic health, more than 40 percent do not get enough vitamin C, and half are not getting enough vitamin A, calcium and magnesium (3). Smokers, the elderly, people who are obese, ill or injured often have elevated needs for vitamins and minerals. Accor- ding to the scientists, it is fine to tell people to eat better, but it is foolish to suggest that a multivitamin which costs a nickel a day is a bad idea. Even though most clinical trials often significantly understate the value of vitamin supplements, the largest and longest clinical trial of multivitamin/mineral supplements found a reduc- tion of total cancer and cataract incidence in male physicians over the age of 50 (6, 7). It suggested that if every adult in the U.S. took such supplements it could prevent up to 130,000 cases of cancer each year. In addition to reducing cases of cancer, it could also compliment good basic health by supporting normal body functions, metabolism and growth.


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  6. Gaziano J. M. et al. Multivitamins in the prevention of cancer in men. The Physicians' Health Study II – Randomized Controlled Trial. JAMA. 2012; 308:1871-1880.
  7. Christen W. G. et al. A multivitamin supplement and cataract and age-related macular degeneration in a randomized trial of male physicians. Ophthalmology. Published online November 2013.