There is no doubt in my mind that the quality of scientific research has deteriorated in the scientific literature in the last decade. It may be argued that this is a reflection of the growing amount of knowledge and the lack of novel areas for groundbreaking studies. However, I would argue that this is not the case as some novel and interesting nutritional studies have been published in the last ten years, and many have opened up new channels for subsequent studies. The problem more likely results from the same problems that affect other areas of life, but more on this later. Whatever the cause, I am astounded that many studies in the nutritional literature are accepted for publication having supposedly passed through both peer review and editorial checks. However, I have recently read two vitamin D studies, which left me questioning the point of peer review at all. While one paper contained a simple schoolboy error, the other left me wondering as to the purpose of the research or why it was necessary.
The first study contained a mistake1. This sometimes happens, and is unfortunate, but in the case of this study I rather feel the error was more confusory than typographic in nature. Normally, the 25-hydroxyvitamin D levels of plasma are reported with the units as ng/mL or nmol/L, the American and British units of the measurement respectively. Strangely the authors decided to report the 25-hydroxyvitamin D in μg/L. Now 26 μg/L is the same as 26 ng/mL but why they chose to use a unit that I had not previously seen associated with vitamin D seemed strange. It is usual to then in brackets give the British equivalent unit which in this case would be 65 nmol/L. However the authors reported the converted British figure as 65.0 pmol/L, a factor of 1000 too low. This may seem picky, but science is about accuracy, and the manuscript of this paper had supposedly been through peer review and none of the reviewers bothered to highlight the unusual use of units or the mistake, that appear incidentally in the abstract.
Surely any vitamin D researcher would instantly recognise the usual units? That is in fact how I was alerted to the mistake. Just why the authors chose to use a non standard unit for vitamin D is also unknown. Of course if you use μg/L the equivalent British unit is pmol/mL. I would suggest that they used the unusual unit, this lead to confusion over the British conversion and no one bothered to check. In another recent study published in the same journal, the authors reported the determinants of vitamin D status in postmenopausal women2. The study used retrospective data from a large cohort of subjects that included information on plasma levels of 25-hydroxyvitamin D and various lifestyle and nutritional parameters such as sun exposure and vitamin D intake. Not surprisingly the authors reported that the determinant of 25-hydroxyvitamin D plasma levels were the total intake of vitamin D (food plus supplements), the years of vitamin D supplement use, the time spent outdoors and the regional solar radiances.
The authors also reported that the correlation between dietary vitamin D intake and plasma levels of 25-hydroxyvitamin D were stronger between those that spent less time exposed to the sun and that total vitamin D intake explained most of the variation seen in plasma 25-hydroxyvitamin D levels. Just how this study was novel and how it passed peer review I am not sure. There are plenty of studies that contain data showing that vitamin D intake and sun exposure affect plasma levels of 25-hydroxyvitamin D. Concluding that ‘dietary factors and sun exposure remain important determinants of vitamin D status in postmenopausal women’ seems to me like stating that flying the Atlantic is quicker than sailing. Now while it could be argued that the science here is self evident, this is not the problem I have with this study. The problem I see is that the results have already been published and there is nothing here that cannot be found elsewhere in the literature. And this brings us back to the problem with modern research.
The main problem I see with modern research stems from the same problem that infests most areas of modern life. Pressure is put onto researchers to meet targets, and scientists, who should be methodical and thoughtful, become paper publishing machines. Quantity has replaced quality as the main determinant of success and as a result we see mistakes that should not occur and the regurgitation of previous findings with a twist. Sure we may know the correlates of vitamin D with 25-hydroxyvitamin D in young men, old men, black women and rats, but if we can repeat the research but just change the subject group, we have ‘novel’ research. This creates research ‘noise’ that drowns out the important findings behind mountains of low grade and low quality studies that are not in any way novel or interesting. These two studies are not isolated examples, they are unfortunately becoming the norm. Just how we get out of this mess I am unsure, but something needs to change to restore some semblance of quality control in science.
RdB
