Taylor Hill/Getty Olivia Munn
The X-Men actress, 40, tells PEOPLE that she had been feeling off for years before she was able to get a diagnosis.
"I wasn't really sure what was going on with me," Munn says, as part of an interview for her Poppi partnership. "I was going through a lot of different ailments for years and not knowing what was happening."
With the help of a team of five doctors at UCLA, Munn was diagnosed with fibromyalgia, a common but incurable disorder that causes widespread muscle pain, fatigue and sleep and memory issues, that are often triggered by stress.
"I had to change my wellness routine pretty significantly," she says. "I had to be super thoughtful about what I put into my body. I had to start eating gluten-free, dairy-free and sugar-free — I had to cut out a lot of things that I was used to having every day and things that I really loved."
That became a bit more of a challenge for Munn because of the timing — she was heading out to Italy the next day.
"If you can imagine getting diagnosed with an autoimmune disorder and then the very next day flying to Italy to film for a month and being told you can't have any sugar, any dairy, any gluten," she recalls. "This was literally the next day. I was like, 'Are you kidding me?' "
But Munn had to do it, or risk getting sicker.
"My situation was at a place where it was like, 'You're either going to go down a path where you're going to get multiple autoimmune diseases, or you have to stop now and we can try to get you better,' " she says. "It was like, 'These are your choices.' And so I had no choice, I was feeling so bad. I had to really listen to the doctor's orders and cut all these things out."
One of Munn's doctors also gave her an "interesting" piece of advice — to appreciate her food, because fibromyalgia is linked to happiness and stress.
"He said, 'You need to really work on your gut health, but the most important thing I can tell you is that whatever you eat, you need to really love it. It's not just about eating the healthy things and you're not liking it. You have to find what you love to eat and drink because that will make a difference, because all the research has shown that when you're happy, you create chemicals that are good for your whole body and your gut health as well. When you are unhappy and you're doing things that you don't like, you're eating things you don't like, you will create other things in your body that are not good for you. In order to keep yourself healthy, you have to find things that you enjoy,' " she says. "That was so impactful for me."
Now, Munn focuses on maintaining a happy diet free of the foods that affect her disorder, regular mediation to manage her stress and making sure to drink 3 liters of water a day. Once an avid soda drinker, the star switched to Poppi, a sparkling prebiotic drink, to curb her craving.
"It's under control as long as I continue to work out and as long as I eat healthy and stick to the restrictions and meditate," she says. "Those are the really important things."