The Ile191Val (rs35874116) polymorphism in TAS1R2 gene will be detected by using a TaqMan allelic discrimination assay (ABI number C_55646_20; Applied Biosystems, Foster City, CA) with real-time polymerase chain reaction on an ABI 7000 Sequence Detection System (Applied Biosystems). Conditions of the polymerase chain reaction is 95 degree Celsius for 10 min and 40 cycles of 95 degree Celsius for 15 s and 60 degree Celsius for 1 min. Genotyping will be verified by using positive control subjects in each 30-well plate as well as rerunning ≥ 5% of the samples, which were 100% concordant.