Sometimes the conflict is really easy to see. The stereotype of the used car salesman telling you that he knows the little old lady who used to own this car, and she only ever used it to drive to the grocery store and church, and followed the maintenance schedule religiously. The restaurants who all have an award winning clam chowder, or barbecue or whatever regional specialty they think people will buy.
But sometimes, it’s not quite so clear. Conflicts can be hidden, as corporations will sometimes create a research arm or foundation with a different name in order to conduct research. Additionally, someone has to pay for studies, and companies are required to have studies to prove the safety and effectiveness of their product. Neutral parties are unlikely to fund these studies, so how can we know if a study with that inherent conflict of interest is still valid?
Here are some tips:
Always look for a conflict of interest statement. Could be in the abstract, or might be buried at the end of the full text by the references. Disclosing a conflict of interest does not automatically invalidate the study, but it should raise your level of critical thinking.
Consider where it is published. Studies published in peer reviewed journals have been reviewed by experts for any signs of data manipulation or trouble. Look into the publisher. Not all journals that say they are peer reviewed actually are peer reviewed. Fake journals that will take any article they are paid to publish are, sadly, a thing. Look at reviews of the journals. Be highly suspect of any research that is only published on the web site of the company selling the product.
Read and evaluate the full study for yourself. Look at how it was designed, who participated, and the results. See if the conclusions makes sense. For example, a (totally made up) study that asked 5000 essential oil representatives to evaluate how the oils have improved their lives and quantified that data, concluding that essential oils should be in every home in the country just might have a bit of a conflict of interest.