My shih tzu was on various Science Diet formulas from 2002-2007

with a break somewhere around 2005-6 of pre-packaged raw dog feed, then raw/cooked organic buffalo meat sold for human consumption. Before that, from 1997-2002, she was on IAMS (



) mainly their chicken formula since the lamb and rice made her stink of lamb game-yness. She did start off '97 on Diamond Dog Food and did well on it for one oversized bag's worth. And before '97, she was on random table scraps and I'm not sure what kind of dog chow.
Science Diet at the time seemed to be one of the most expensive brands found in the readily available chain pet supply stores. It says, "formulated by veterinarians" so one would think it was a safe choice and the vet I used at the time sold that brand as well.
My previous choice of IAMS was because of exposure. I was a sucker for advertisement, and that seemed most advertised and so I thought it was more "premium" than brands like Puppy Chow or Kibbles & Bits or Pedigree even. Those seemed more "common". I never thought of doing online research on it. I guess I used the internet for other things back in the day.

I only remember at some point though, coming upon some IAMS hate statements and found a "ihateiams.com" type of website (can't remember exact url) but it wasn't so much going on about the low quality food as it was a concern about their use and treatment of their animals employed at their facilities for product testing. That's when I switched both my cat and dog to SD.
My cat's been on SD from '02 to current as I've been mixing in Wellness with her SD food though she keeps picking out and dropping the Wellness all over the place while digging for the SD kibbles. She then would eat the Wellness if there really isn't any SD left and we ignore her vocal complaints for her old food. When the bag of SD is finished, she will likely be on Wellness 100% except that the hubby wants to give her something else she might like better as he thinks she really doesn't like Wellness. She actually didn't protest the switch from IAMS to SD.
Ellie May would be my advisor of choice with regards to diet and nutrition queries also.