It's hard to understate the number of misleading health reports and health advice out there. First there's the problem of alternative-medicine quacks (visit the Enemies of Reason tag to learn more about them); then there are also problems with misleading journalistic reports that confuse some shallow correlation with a causal connection; then we have pharmaceutical companies who publish only results favorable to their products while keeping those that aren't as confidential under legal technicalities like trade secrets; then we have scientists who don't always conduct sufficiently rigorous studies and experiments; etc.
Thankfully, there are people like Ben Goldacre, who in this TEDTalk presentation exposes some of the ways in which industries and journalists can distort evidence and statistics to get you to buy their products, or to scare you from buying products from their competitors, or just to sell more copies of their journals and keep their ratings going, etc.
And you can't miss Ben Goldacre's awesome rant on the placebo and nocebo effects.