Expert opinion
Micronutrient studies: a challenge for journalists
1 October 2012
Studies enjoy great popularity among journalists. They cannot be argued against, because they are objective.
27 March 2012
“Adequate intake of micronutrients, such as vitamins, minerals, and trace elements, is essential for human health. This has been demonstrated by a variety of studies. Meta-analyses summarize the results of many different studies and thus draw upon a broad base of data. However, a conclusive summary can only be compiled if similar conditions exist in the individual studies involved.
The recent review by Bjelakovic et al. (1) does not meet this fundamental require-ment for scientific validity. For example, of the 615 initial individual studies on antioxidants, the authors excluded 537 of these from their further analysis, including all the studies in which no deaths occurred. Only the remaining 78 studies (13 percent) were analyzed, i.e., the studies in which deaths were recorded. Yet only 25 of the 78 studies were designed as mortality studies. Nevertheless, studies in which mortality was not systematically examined – i.e., studies that should have only been used to generate hypotheses (to be tested in further studies) – were also included in the mortality considerations. This selection error represents a significant methodological flaw that has led to biased results.
Above all, each of the studies in the meta-analysis comprised extremely different dosages and observation periods (i.e., ranging between 28 days and 12 years), and are thus not comparable as such. For example, the vitamin E dosage varied from 10 to 5,000 IU in the individual studies. This is methodologically inadmis-sible and therefore does not constitute a basis for general conclusions. Despite being based on such dispa-rate, raw data, this meta-analysis derives a not more than 3% higher risk of death from antioxidant supple-mentation – and that using a statistical model with fixed effects. There are, however, no significant results derived using a model with random effects, which, given the heterogeneity of the studies, would be of greater significance. In this respect, drawing general statements about, or even basic warnings against, dietary supplementation with micronutrients from this study is not vindicable.”
1 October 2012
Studies enjoy great popularity among journalists. They cannot be argued against, because they are objective.
15 July 2015
Helena Pachon is Research Associate Professor at the Rollins School of Public Health in Atlanta, USA. Her team has been involved in a systematic assessment regarding the effectiveness of the fortification of flour to prevent anemia. They found that each year of flour fortification was associated with a 2.4% reduction in the prevalence of anemia. There was no reduction in those countries that did not fortify.
14 November 2013
A new US review concluded that there is only limited evidence that vitamin and mineral supplementation can prevent the development of cancer or cardiovascular disease in healthy people without known nutritional deficiencies. The researchers acknowledge, however, that the data analysis has weaknesses.