Saliva sampling: six samples of unstimulated whole saliva (UWS) fro m each subject will be collected (one at baseline, one right after the run-in period and one at the end of the intervention period). For USW collection, the participant will be sitting in a comfortable position with the head slightly bent. The participant is asked to keep the eyes open and make as few moves as possible, including swallowing. Then, he/she is asked to rinse the mouth in water and spit it out again. Thereafter, he/she is instructed to let saliva flow out of the mouth down a designated plastic cup for ten minutes. Aliquots of saliva (1.5 ml) will immediately be placed on ice and stored in a freezer at -80 °C until further analysis.