"Useful" has to be taken in context.
The issue with so many published studies are:
1. Inappropriate population (i.e. untrained college students)
2. Funding by group with interest in outcome
3. Statistical analysis couched in a lot of obscure language to obscure the results.
Look at the debacle with regards to The China Study, and how certain correlations were publicized and certain correlations were not.
Unless you are in a research field, or have a bit of a jones for the research, most scientific journals are essentially worthless to someone just interested in training.