Sugar is acknowledged to cause tooth decay. Ninety-eight (98%) of Americans have caries, while studies of the skulls of peoples who did not consume sugar show a caries rate of about 2% (Price 1945).
How exactly does sugar damage teeth? It's very interesting, and not widely known, that sugar reverses the flow of dental lymph. The pulp of the tooth is extremely active metabolically, generating a high pressure which pushes lymph out of the tooth through tiny tubules in the dentin and enamel. When sugar is eaten, the internal pressure within the tooth falls and fluids from the mouth are drawn into the tooth. Unfortunately, these mouth fluids include the bacteria in the mouth and acid wastes of plaque bacteria which cause decay. Thus, no amount of oral hygiene can entirely prevent sugar from causing tooth decay (Steinman 1984).
A typical American breakfast supplies an enormous amount of sugar and starches which are very rapidly converted to blood sugar. This drives the blood sugar up rapidly, causing the pancreas to secrete too much insulin. Insulin causes the blood sugar to fall too quickly which is known as hypoglycemia. Many Americans eat this much sugar at two or even three meals per day.