Not all studies are equal, As much as it would be great to have belief in all scientific studies, there is a lot of junk science out there,
For example this one I read today
Oral Supplementation Using Gamma-Aminobutyric Acid and Whey Protein Improves Whole Body Fat-Free Mass in Men After Resistance Training. - PubMed - NCBI
It would be great to believe this substance was effective for building fat free mass (muscle) and if this tudy is to believed then this substance does, however there are a few problems with this study.
The first being that it is funded my a manufacturer of the supplement and all the scientists are employees of the manufacturer, this is a big red flag indicating that the results may not be as they seem.
Small study size is another problem, results can appear more significant in a small study. In some studies cannot help being small due to the nature of what is being studied, however this is not one of those,
While the two groups were "random" in such a small study if one group has more untrained individuals than the other group then the results will not be a true indicator of how well the supplement works. If major variables that have an impact on the outcome are not controlled the outcome cannot be trusted. other major variables that were not taken into account in this study was diet quality of the individuals, other supplements in use by the participants, Physical activity levels outside of the study were not considered etc.
The result, while written in a way that the results sound great, no actual results data is provided
This type of study only benefits the supplement manufacturer who can now include claims such as "scientifically proven to build muscle" when in reality nothing was proven. These kinds of studies are very common and lead to all sorts of marketing hype under guise of science.