Reason why a person can have yellow teeth will very.  There are people that teeth are naturally yellow in color. Not everyone is has naturally white teeth, and unless you use advanced whitening methods you can not change your natural tooth color.  Aging also has an effect on your teeth. Yellowing of your teeth is a natural aspect of aging. Food and drinks can stain your teeth and over time can make your teeth look dark or yellowish. Smoking will discolor your teeth. Poor dental and oral hygiene can also cause your teeth to yellow or to become discolored. Whatever the reasons a dentist can help to address the issue and make your teeth look naturally white again.