Studies published in reputable scientific journals like Nature are usually not bogus, especially if they were already replicated. However applying the results to everyday life is tricky - one certainly must not assign more meaning to them than the authors did, but also probably even less than that. Remember the mantra: the experiment shows only what the experiment shows, not the great opportunities you want it to show.
Note that "nutritional science" is not a hard science, their track record is abysmal. The nearest hard science we have to that is microbiology.
As a rule, all observational studies are junk - too many hidden variables, etc. There are some exceptions to it, but you will be best served by just assuming junk. If you're not willing to discard a particular observational study at least check if the study controls for obvious hidden variables - wealth, age, sex, health level, etc. For example there were "studies" that showed red wine correlates with good health, and the coverage was that we should all drink red wine. But guess what - rich people drink red wine and live longer because rich. Controlled for wealth, the effect disappears.