They won't kill you but these white lines mean that the chicken's growth was artificially accelerated. This means that the meat will be fattier, of a lesser quality, and may be tough when cooked.
Discover our latest podcast
The growth of livestock is increasingly based on genetics, especially with selective breeding. The main cause for concern is the addition of new substances that force chickens to grow disproportionately and causes some of them to have muscle dysfunctions. These muscle dysfunctions then show themselves in those little white lines you see on your chicken. So use them as a marker of the quality of the meat you are buying.
Check out the video above to find out more!