Liam spoke on Radio 5 live and said: “I am now addicted to BBC decaf tea.”
The actor made the switch due to health conditions he was suffering.
He explained: “I was getting shooting pains in my leg, cramps in the middle of the night.
“A friend of mine set me up with this massage therapist who does all the dancers on Broadway and he worked on me.
The body makes lactic acid when it is low in the oxygen it needs to convert glucose into energy.
Lactic acid build-up can result in muscle pain, cramps, and muscular fatigue.
These symptoms are typical during strenuous exercise and are not usually anything to worry about as the liver breaks down any excess lactate.
Lactic acid in the muscles will cause them to ache, feel sore and underperform, warn experts.
In the longer term, the lactic acid can get stuck in the muscle and form crystals which massage therapists refer to as knots.
The knots then get more waste stuck to them and get larger.
Research shows that caffeine, a stimulant with ergogenic properties, increases blood lactate levels.