There was slight incidence of caries in pre-European Bantu. The most primitive modern Bantu have an incidence of the same order; about 30 percent of all adults have caries—two or three carious teeth per carious mouth. Natives taking to a European mode of living show marked increases in caries, which approach or equal the high incidence among present-day Europeans. Considering first the major cause of caries—and ignoring, for the time being, the reasons for caries in a trivial number of teeth in the primitive native—an attempt was made to correlate presence of caries with various items of diet.
This led to the conclusion that one or more of the following factors causes caries in natives who take to a European manner of living, and hence in Europeans themselves : (a) European bread, (b) machine-ground mealie meal, (c) foods containing refined sugar. Further reasoning and experimental findings led to the conclusion that crude cane-juice, whole mealie and whole-wheat grains contain a ” protective agent,” which tends to inhibit the injurious action of carbohydrate on teeth; which is removed, or reduced in concentration, in the process of refining; and which exerts its effect otherwise than by preventing or reducing acid fermentation of carbohydrate in the mouth.
It was reasoned that crude cereal grains themselves were unlikely to be a major cause of caries, since primitive Bantu subsist on a diet containing a very large proportion of cereal. Sugar, as it occurs in nature, is not a major cause of caries. Natives in sugar-cane fields and factories chew cane regularly, yet neither in this nor in other countries have they been more prone to caries than their fellows. Fruits contain much sugar, yet have never fallen under suspicion as producers of caries. Therefore cereals and sugars as they occur in nature are harmless, but the refined states of these foods produce caries. To test this deduction, teeth were incubated in media containing sugar or cereals mixed with saliva. Refined white sugar produced decalcification in a high proportion of teeth, crude juice in very few. Whole mealies and whole wheat produced this change in a significantly smaller proportion of teeth than the refined meal and flour made from these grains. A mixture of calcium lactate and sodium glycerophosphate, added to refined sugar and cereals, caused marked reduction in number of teeth attacked. Calcium glycerophosphate was even more effective as a protective agent. In none of the tubes was the pH significantly different from that of the controls ; therefore these protective substances, like the ” protective agent ” postulated for crude cane-juice and cereals, do not exert their effects by controlling pH.
References: S. Afr. J. Med. Sc. (suppl.), 1935 ; J. Den. Res., 1937.