Every day we hear or read about X (garlic, coffee, swimming,etc ) being associated with Y (death, heart attacks, cancer, depression, etc), and almost all of these reports are wrong. One problem is that the reports confuse association and causation, but a bigger problem is that associations are not real. John Ioannidis, the Stanford professor who is the leading scourge of poor science, illustrated the problem at a conference in Chicago with an analysis of foods linked with cancer. This is how I reported this passage of his talk.
“Ioannidis illustrated his theme [of most published research findings being false] by describing a study in which colleagues randomly selected 50 ingredients from America’s most popular cookbook and then searched PubMed to see which of the ingredients had been linked with either increasing or decreasing the risk of cancer. The answer was 40. Large numbers of studies had shown so, and no doubt hundreds of thousands of media reports will have spread the message to the public. In fact, said Ioannidis, a meta-meta-analysis shows that the scientific studies are “correct” in almost no cases. (The public may be smarter than the scientists in discounting and ignoring these reports, although an unfortunate result is a public scepticism about science that leads many to accept the assertion that there is no evidence for human activity causing climate change.)”
You can read Ioannidis’s original paper at: https://www.ncbi.nlm.nih.gov/pubmed/23193004
And you can read my blog that repoted on his whole speech at:http://blogs.bmj.com/bmj/2013/09/09/richard-smith-time-for-science-to-be-about-truth-rather-than-careers/