SUCROSE

As shown in Figure 1, sucrose is a dimer of glucose and fructose. Soon after it is eaten, this dimer is hydrolyzed to produce separate glucose and fructose molecules. Fructose, sometimes referred to as "fruit sugar,'' is also contained in many foods. Glucose is even more common. It is a major metabolic constituent, and it has many other uses. For example, cellulose, the primary structural component in many plants, is a polymer of glucose.

It is, as yet, not definitively known whether or not a change in diet in which the intake of sucrose is increased far beyond that to which the human body was previously exposed is harmless, harmful, or beneficial. This is a continuing subject of research. It is a complicated problem because foods are made up of tens of thousands of different chemicals in variable amounts. Also, humans are notoriously difficult research subjects, so controlled experiments are difficult.

Twenty five years ago, a remarkable biochemist, Milton Winitz, developed a completely defined chemical diet upon which humans can live indefinitely. He marketed this diet as "Vivonex 100.'' It may still be available. The Winitz diet was made entirely with purified chemicals - amino acids, vitamins, minerals, fats, and carbohydrates. The amounts of chemicals in the diet could not be optimized for each individual person, since the necessary information was unknown. The formula was an average that supported satisfactory health in most people.

One interesting property of this diet is that it requires no digestion and contains no waste. All of the constituents are physiologically absorbed and utilized as provided. Therefore, an individual eating this diet has no solid waste. The colon just rests with nothing to do. This makes the diet useful in treating some digestive disorders. Experiments showed that this rest was not harmful. After many months of disuse, the colon starts working again as soon as it is given something to do.

The original carbohydrate source in Vivonex 100 was solely glucose. In this form, Vivonex 100 was extensively tested on convict volunteers who were biochemically and physiologically monitored during a prolonged period ingesting only this diet.

Winitz found that he could control blood cholesterol over a range of a factor of 1.5 - solely by exchanging glucose for sucrose (or, perhaps, glucose for fructose by way of sucrose). See M. Winitz, D. A. Seed-man, & J. Graff, Am. J. Clin. Nutrition 23, p 525-545 (1970). This work, however, does not mean that sucrose always causes high cholesterol. A complete diet has numerous chemicals - the absolute amounts and ratios of which may affect this result.

In another experiment, when we were studying cancer as a function of diet in mice (See "Suppression of Squamous Cell Carcinoma in Hairless Mice by Dietary Nutrient Variation'' by A. B. Robinson, A. Hunsberger, and F. C. Westall in Mechanisms of Ageing and Development 76, pp 210-214 (1994)), we found that replacement of 20% of the ordinary mouse diet by sucrose (approximately the percentage eaten on average by Americans) reduced the growth rate of cancer by about 20%. This reduction corresponded, however, to the reduction in cancer growth rate also observed when protein intake was reduced by 20% by other means. The sucrose simply replaced some of the protein. Protein is positively correlated to the rate of growth of cancer. A person with cancer should try not to feed the cancer an enriched diet.

Thousands of experiments have been performed on human health and sucrose. Some of these have been interpreted to mean that high sucrose intake raises the probability of heart disease, cancer, mental instability, tooth decay, and numerous other maladies. Other experimenters claim that high sucrose is harmless - that the observed ill effects are caused by accompanying fat intake or other factors. Almost all of the work on both sides of this issue is correlational in nature. Always remember, however, that correlation does not prove causality.