I happen to come across this article. Nice to know grandpa was right!
http://xfinity.comcast.net/blogs/lifestyle/2014/06/04/egg-yolks-to-eat-or-toss/?cid=hero_media
http://xfinity.comcast.net/blogs/lifestyle/2014/06/04/egg-yolks-to-eat-or-toss/?cid=hero_media