The Malcolm in the Middle star grew up with both actresses as they tried to carve out TV and screen careers as kids, and while he has largely managed to avoid the pitfalls of fame, Bynes and Lohan have not been as lucky.
Muniz claims his decision to move away from Los Angeles and build a quieter life for himself in Phoenix, Arizona helped to save his sanity - and he's encouraging his former friends to do the same.
The actor admits he has not spoken to Bynes, his co-star in 2002 film Big Fat Liar, since she started hitting headlines for all the wrong reasons last year (12), but he has one key piece of advice for both embattled women.
He tells U.S. talk show host Katie Couric, "It's one of those things. I've known all of them - I was good friends with Lindsay, I was good friends with Amanda; I was good friends with everybody...
"I wanna say, just take a step away. It wasn't until I left the business essentially and moved to Phoenix where I went, 'Wow, that (acting) was amazing, I'm so lucky to have experienced something so amazing', because when you're in it it's just your life... I almost just wanna tell them, just go away for a little bit, get away from the world, get away from the photographers and the people following you around and find yourself and maybe you'll be happier."
Bynes has endured a year of bizarre behaviour and driving offences, while Lohan has been in and out of jail and rehab in recent years, and is currently fighting allegations of probation violation.
Muniz has not turned his back on showbusiness for good - he plays drums in rock band Kingsfoil.