The sugar fructose is already well known to be highly detrimental to health in large doses and has been linked with contributing to ills including obesity, type-2 diabetes and an increased risk of heart disease. Further evidence again finds that weight for weight, fructose worsens disease markers more than glucose. It also contributes more to weight gain by reducing fat-burning and metabolic rate, in comparison to glucose.

Fructose is the main sugar found in fruit, but in this form, it is also accompanied by fiber and other nutrients and enzymes that make it easily digestible, with no depletion of minerals or rises in blood sugar levels.

Another form of fructose, high fructose corn syrup, however, has the opposite effect on the body. This artificial form of sugar, the main sugar in soft drinks, has a toxic effect on the body; it inhibits digestion, causes chemical imbalances and strips the body of vitamins and minerals.

High fructose corn syrup is made cheaply by the chemical treatment of the starch in corn, and contains fructose and glucose in roughly equal measure.

This sweetening agent 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 savory 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 [1]. In this study, healthy, normal-weight men aged 20-50 consumed in beverage form either:

1. 40 g of fructose a day (medium fructose)

2. 80 g of fructose a day (high fructose)

3. 40 g of glucose a day (medium glucose)

4. 80 g of glucose a day (high glucose)

5. 80 g of sucrose a day (high sucrose)

Some of the men consumed none of these drinks and were counseled 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, in that it speeds the metabolism and helps curb appetite)

All of this suggests 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.

Fructose vs glucose and weight gain

This research involved feeding overweight and obese men and women fructose- or glucose-sweetened drinks for 10 weeks [2]. Total amount of sugar represented 25 per cent of total energy requirements. So, someone who typically consumes 2,000 calories a day would have consumed 500 calories-worth or 125 grams of sugar.

The study participants were assessed with a range of measurements including:

• fat oxidation (metabolism) after eating

• resting energy expenditure (basal metabolic rate)

The results showed that consuming fructose led to a significant reduction in both fat oxidation after eating and resting energy expenditure. These reductions were not, however, seen with glucose consumption. These findings suggest that, gram for gram, fructose has more fattening potential than glucose.

Admittedly, the amount of fructose consumed in this experiment was quite large (roughly equivalent to 3 cans each day or soda/soft drink). Nevertheless, the study does provide further evidence that fructose can harm health, and is generally more damaging in this respect than glucose.

Research Paper Details:

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

2. Cox CL, et al. Consumption of fructose-sweetened beverages for 10 weeks reduces net fat oxidation and energy expenditure in overweight/obese men and women. European Journal of Clinical nutrition. advance online publication 28 September 2011.