Were any of these papers published in reputable journals with reputable peer reviewers?
They appear to be only published by the university without any peer review (i.e., http://researcharchive.lincoln.ac.nz/handle/10182/3953?mode=simple). They would never make it into any journal with reasonable standards for methodology and statistics.
Also, I think I have come across as too negative towards observational studies. In many cases they are the best you can do but care is always needed in their interpretation. Asserting any possible causal relationships requires including prior evidence and careful arguments.