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In Britain and other countries, the incidence of caries has risen roughly parallel with rising consumption of sucrose. The incidence of caries has risen in spite of the much greater consumption of so-called ‘protective’ foods, namely dairy products, meat and fruit, in recent years. As a consequence of this more varied diet, carbohydrates overall have formed a smaller proportion of the diet. Nevertheless, sucrose forms a higher proportion of the carbohydrate component.
Where there has been a change from simple natural diets to a Westernized diet, as in Alaska, caries has increased sharply, and Eskimo children now have a caries incidence at least as high as other American children. A similar state of affairs is developing in Africa as sweet eating and sweet between-meals ‘snacks’ have become popular. In Nigeria many of the older adults are still totally caries-free but the prevalence of dental caries among children and young people who have picked up sweet eating habits is rising rapidly. This effect has also been strikingly well documented in the population of Tristan da Cunha who, up to the late 1930s, lived on a simple meat, fish and vegetable diet with a minimal sucrose content and had a very low caries prevalence. With the adoption of westernized diet, the caries prevalence had risen up to eight-fold in some age groups by the mid-1960s. Even in Europe, in the 1930s and 1940s there were isolated communities such as the Outer Hebrides or the Lotschental in Switzerland, where dental caries prevalence rose 20-fold or more when sucrose and sweets became widely consumed.
The effect of limiting sucrose consumption was shown on a vast scale in wartime. Those countries which suffered food shortages during the 1939-45 war had severe restrictions, mainly of meat, fats and sucrose. To maintain an adequate caloric intake, overall consumption of starchy carbohydrates rose considerably. As sucrose became more plentiful at the end of the war, caries prevalence progressively rose.
In Japan also, rising caries prevalence has been associated with rising sucrose consumption. Towards the end of the Second World War sugar consumption and caries levels were very low. More recently, Japan is one of the few countries where sucrose consumption, from 16.5 kg per head in 1961, nearly doubled in 1970. Caries prevalence has risen in parallel. Unlike most other countries, this picture has not been significantly masked by use of fluoride toothpastes where the market share of fluoride toothpastes is only 15%.
Caries has become epidemic only in relatively recent years as sucrose became cheaper and widely available. In Britain there was a sudden, widespread rise in sucrose consumption in the middle of the 19th century. This resulted both from the falling cost of production and, in 1861, the abolition of a tax on sugar.
Evidence from exhumed skulls confirms the low prevalence of caries before sucrose became widely available and the steady rise in prevalence thereafter. Patients unable to metabolize fructose as a result of an enzyme deficiency cannot tolerate fructose-containing foods including disaccharides such as sucrose where fructose forms part of the molecule. These children therefore learn to avoid all sucrose-containing foods and have an unusually low incidence of caries.
Experimental Studies on Humans
In the Vipeholm study over 400 adult patients were studied in a closed institution. They received a basic low-carbohydrate diet to establish a baseline of caries activity for each group. They were then divided into seven groups which were each allocated different diets. A control group received the basic diet made up to an adequate calorie intake with margarine. Two groups received supplements of sucrose at mealtimes, either in solution or as sweetened bread. The four remaining groups received sweets (toffees, caramels, or chocolate) which were eaten between meals.
The effects of sucrose in different quantities and of different degrees of adhesiveness, and of eating sucrose at different times were thus tested over a period of 5 years. Caries activity was greatly enhanced by the eating, between meals, of sticky sweets (toffees and caramels) that were retained on the teeth. Sucrose at mealtimes only, had little effect. The incidence of caries fell to its original low level when toffees or caramels were no longer given, and caries activity was very slight in the control group having the low carbohydrate diet.
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