The star, who was previously dubbed as Australia's Sexiest Vegan by PETA, made the announcement in an interview with Men's Health.
'I felt great'
"The first two years [of eating vegan], I felt great. I felt my energy was high. I felt like my body was strong, cardio was high, everything felt really good," Hemsworth told journalist Lauren Williamson.
"[But] February last year I was feeling really low and lethargic and wasn’t feeling good generally. And then I got a kidney stone."
It is reported that Hemsworth was dealing with a calcium oxalate stone - which he blamed on his morning smoothie that consisted of 'five handfuls of spinach, almond milk, almond butter, and vegan protein'.
"That was what I considered super healthy and doing the right thing. I had to completely rethink what I was putting in my body," he added.
Treating kidney stones
Renowned plant-based medic Dr. Michael Greger states 'anyone can overdo the three high-oxalate greens—spinach, beet greens, and Swiss chard' - and recommends people opt for other greens, such as kale, collards, or arugula.
In his post Treating Kidney Stones with Diet, Greger concludes: "The most important things we can do diet-wise is to drink 10 to 12 cups of water a day, reduce animal protein, reduce salt, and eat more vegetables and more vegetarian."
He adds: "Excessive consumption of animal protein poses a risk of kidney stone formation, likely due to the acid load contributed by the high content of sulfur-containing amino acids in animal protein."
You can learn more about kidney health at nutritionfacts.org