1954: Scandinavian dentists had for years puzzled over the abysmal dental health of the population. In the 1930s, for instance, 83 per cent of 3-year-olds had tooth decay. What were the causes? A deficiency disease? A poor diet? Excessive carbohydrate intake?
The Vipeholm dental caries study was intended to provide answers. Experimenters at the Vipeholm mental hospital in Sweden first tinkered with the vitamin intake of inmates, and when that produced no significant changes in levels of tooth decay, fed them each up to 24 sticky toffees a day. That produced a marked increase in cavities, demonstrating a clear link between sugar consumption and tooth decay.
Feeding exaggerated quantities of toffees to unwitting human beings resulted in lots of ruined teeth and, belatedly, lots of ethical questions, but it also produced much valuable evidence about the causes of tooth decay.
Source: Prevention of Oral Disease, ed. J.J. Murray (1996), pp. 11–13