Evidence from epidemiologic studies
Numerous worldwide epidemiologic studies during the 20th century have shown that
caries prevalence is low in developing countries or populations living on a local,
carbohydrate-rich diet, based on starch instead of sucrose. Figure 51 shows sugar
consumption in 1977 in a number of countries worldwide. Consumption is extremely
low in China, and caries prevalence among 12 year olds is very low. On the other
hand, sugar consumption in Japan is only about half that of other industrialized
countries, but caries prevalence is moderate to high.
In contrast, for the last 30 to 40 years, sugar consumption in Sweden has remained
persistently high, at about 120 g/per day (Fig 52). At the same time, caries prevalence
has decreased from very high to low. Since the early 1950s, it has been “common
knowledge” in Sweden that caries is “caused” by frequent intake of sweets. Despite
this, over the last 30 years, indirect sugar consumption in the form of sticky sweets,
cakes, and so on has increased from about 30% to more than 60% of total sugar
consumption (see Fig 52). The dramatic reduction in caries prevalence is therefore
attributable not to a reduction in dietary sugar but to a marked improvement in oral
hygiene habits, an associated widespread, regular use of fluoride toothpaste, and
needs-related professional preventive measures.
However, comparison of international data discloses an association between sugar
consumption and caries development. Using information on sugar supplies in various
countries, obtained from food balance sheet data prepared by the FAO, and data on
caries prevalence from the World Health Organization for 6 year olds in 23 nations
and 12 year olds in 47 nations, Sreebny (1982) demonstrated a significant positive
correlation between the quantity of sugar available per capita in a country and caries
prevalence in 12 year olds, but not in 6 year olds. In both age groups, the availability
of less than 50 g sugar per person per day in a country was always associated with
decayed, missing, or filled teeth scores of less than 3. However, this type of
epidemiologic comparison is flawed: Sugar availability cannot directly be
extrapolated to consumption specifically by 6 or 12 year olds. Both caries prevalence
and sugar consumption vary among different age groups within each country.
In wartime, the availability of sugar is usually restricted. In Japan, annual sugar
consumption fell from 15 kg per person prior to World War II to 0.2 kg in 1946.
Many attempts have been made to relate the level of sugar consumption before,
during, and after World War II to caries prevalence in the children: In Norway,
Finland, and Denmark there was a clear relationship between sugar consumption and
caries development in permanent first molars in children.
One of the most thorough literature surveys was made by Sognnaes (1948), who
reviewed 27 wartime studies from 11 European countries, involving 750,000 children.
Reductions in caries prevalence and severity were observed in all studies. Because of
the high prevalence of caries in Europeans, reductions in severity were usually greater
than reductions in prevalence. Sognnaes observed that, in many of the studies, there
appeared to be a delay of about 3 years between the reduction (or increase) in sugar
consumption and a reduction (or increase) in caries severity.
