Table sugar, the form of sugar individuals generally spoon into their tea or coffee or use when making, say, cakes and puddings, is comprised of sucrose. Sucrose is technically termed a ‘disaccharide’, a term used to describe sugars which are comprised of two individual sugar molecules joined together. Those two sugars, in the case of sucrose, are glucose and fructose, and when sucrose it is digested down to its constituent sugars prior to absorption into the bloodstream.
The glucose in sucrose undoubtedly contributes to the glycaemic load of the diet, and the more sugar someone eats, the greater the rise in blood sugar levels. More glucose in the bloodstream means more insulin, of course, which as we know can contribute to health issues such as insulin resistance, Type 2 diabetes, heart disease and, of course, weight gain.
In contrast to glucose, fructose has traditionally enjoyed a healthy reputation, mainly on the basis that it does not raise blood sugar levels. Fructose is also the predominant sugar in many fruits – something which tends to bestow it with an image of healthiness.
In recent years, though, a steadily growing mound of research demonstrates that fructose, while it does not raise blood sugar levels directly, can nevertheless have some profoundly toxic effects on the body. Interest here has been sparked, at least in part, by the fact that increasing amounts of the sweetening agent ‘high fructose corn syrup’ (HFCS) are making their way into the diet. HFCS is made cheaply by the chemical treatment of the starch in corn, and contains fructose and glucose in roughly equal measure.
HFCS began being used in food production in meaningful quantities in the 1970s, but these days contributes substantially to our diets as an ingredient in foods such as breakfast cereals, cereal bars, baked goods such as biscuits and cakes, pre-prepared desserts, sweetened yoghurts and soft drinks, as well as some more savoury foods including cooking sauces, condiments (e.g. ketchup) and crackers.
The potential for fructose to harm health was further demonstrated by a study published recently on-line in the American Journal of Clinical Nutrition . In this study, healthy, normal-weight men aged 20-50 consumed in beverage form either:
- 40 g of fructose a day (medium fructose)
- 80 g of fructose a day (high fructose)
- 40 g of glucose a day (medium glucose)
- 80 g of glucose a day (high glucose)
- 80 g of sucrose a day (high sucrose)
Some of the men consumed none of these drinks and were counselled on how to reduce the amount of fructose in their diets. The study lasted three weeks. A wide range of body measurements and biochemical parameters were checked as part of the study.
Here are some of this study’s most notable findings:
- C-reactive protein, a marker of inflammation, increased in all 5 groups
- LDL cholesterol size decreased in the high fructose and high sucrose groups (smaller LDL particles are associated with heightened risk of cardiovascular disease)
- General changes in LDL particle size consistent with raised cardiovascular disease risk occurred in the medium fructose, high fructose and high sucrose groups
- Waist-to-hip ratio increased the medium fructose, high fructose and high sucrose groups (higher waist-to-hip ratios are associated with an increased risk of conditions such as heart disease and Type 2 diabetes)
- Fasting glucose levels increased in all five groups
- Leptin levels increased in the medium glucose and high glucose groups (leptin is a generally desirable hormone to have around, in that it speeds the metabolism and helps curb appetite)
Put this all together and one would have to conclude that fructose, as supplied in sweetened beverage from, is worse for us than the same amount of glucose. The best thing, of course, is to have neither.
1. Aeberli I, et al. Low to moderate sugar-sweetened beverage consumption impairs glucose and lipid metabolism and promotes inflammation in healthy young men: a randomized controlled trial Am J Clin Nutr 2011 First published online June 15, 2011