Current Knowledge of the Health Effects of Sugar Intake

Twenty years ago, the common perception was that sugar intake was associated with several chronic diseases: Diabetes, coronary heart disease, obesity, and hyperactivity in children. Sugar was also thought to be the sole cause of dental caries. Recent advances in scientific knowledge, however, have shed some light on the role of sugar in chronic diseases and dental caries. The evidence indicates that sugar is not in itself associated with the aforementioned chronic diseases and is not the sole offender in the development of dental caries. This research brief discusses current scientific knowledge of the health effects of sugar.

Physiology

Despite having been labeled as "empty calories," sugars are truly important compounds from the perspective of the human organism. Humans have retained the ability to synthesize all forms of carbohydrates the body needs from simple sugars. This is not the case with the other dietary macronutrients, fats, and proteins. Following ingestion, all digestible complex dietary carbohydrates are broken down in the gut to simple sugars before they are absorbed into the body. Because simple sugars are all identical chemically, the absorption process cannot distinguish simple sugars resulting from the breakdown of complex dietary carbohydrates from corresponding simple sugars occurring naturally in the foods themselves or from corresponding simple sugars added to foods during processing. Within the body, most dietary sugars are converted to glucose, a major fuel used by all cells and the primary fuel required by brain tissue for normal function. Low levels of glucose in the blood will impair the brain and cause permanent mental impairment or worse--coma or death. The body can store a limited amount of glucose as glycogen, which it can draw upon for less than a day. After this, other sources such as proteins, from the breakdown of body tissues, must be used to synthesize glucose for the cells (15).

Diabetes

The relationship between dietary carbohydrates and insulin resistance (a risk factor for diabetes mellitus, ischemic heart disease, and hypertension) is not clear based on available research (7). In two studies based on a large, prospective study of U.S. women, sucrose and carbohydrate intake were not associated with an increased risk of diabetes (6,27). However, based on the same population, associations were found between a diet with high glycemic load[2] (26) and high intake of refined grains (21) and the risk of diabetes. The general consensus, based on epidemiological studies, is that sugar intake alone is not associated with the development of diabetes mellitus. Sugars fed at levels equivalent to those consumed by the U.S. population do not produce adverse glycemic effects in non-diabetics (23). The effects of sugar intake on glucose tolerance, insulin levels, and plasma lipids are confounded by other dietary components. The American Diabetes Association has also acknowledged, in its nutrition recommendations for people with diabetes, that there is no evidence that refined sugars such as sucrose behave any differently from other types of simple carbohydrates (1).

Heart Disease

The Sugars Task Force of the U.S. Food and Drug Administration (29) presented...