Not all of it is bad, of course. Dedicated health and science journalists often do a fine job of maintaining the necessary level of skepticism when probing the claims of new health research. The recent study of health care coverage "Does It Matter Who Writes Medical News Stories?" confirms as much.
Media though is a business and thus it should come as no surprise that a lot of what passes for journalism is simply the selling of the current product, the narrative that attracted customers in the first place, and the marketing of new and improved products fitting that narrative e.g. breathless reporting about miracle cures and health scares. It's therefore not surprising that TV human interest programs did the worst job of accurately reporting health news.
Takeaway: Stay skeptical, especially when it sounds too good, or too bad, to be true.