High intakes of simple sugars are associated with disease. Natural sugars are found in plant foods such as fruits and vegetables. In general where sugars are found however, they are always accompanied by high amounts of dietary fibre. This fibre delays the absorption of the sugars from fruits and prevents nutrient overload in the liver and as such eating fruits is not associated with detrimental health effects. Other sugars in nature are present without fibre, such as is the case with honey, but this source of sugar is protected by bees and is therefore not historically a large source of sugar for humans. Only recently has man discovered processing methods that allow the creation of foods that retain their sugar content but are completely devoid of their protective fibre. The culmination of this tinkering has produced a range of sugar sweetened beverages (soft drinks) that are simple sugar diluted in water with added flavouring. Evidence suggests that such drinks are now a major cause of disease and are driving the obesity epidemic.
The number of studies showing an association between intakes of sugar sweetened beverages and the metabolic syndrome is growing rapidly. For example, in a recent study published in the American Journal of Clinical Nutrition1, researchers investigated the association between intakes of sugar sweetened beverages and the presence of cardiometabolic risk factors (risk factors associated with the development of cardiovascular disease) in adolescents between the ages of 14 and 17 years. The average intake of sugar sweetened beverages amongst the study participants was 1.3 servings per day (335 g per day). Girls with the highest intake of sugar sweetened beverages (more than 1.3 servings per day) had higher body mass indexes, increased risk of being overweight or obese and a larger amount of cardiometabolic risk factors. Both girls and boys with the highest intakes of sugar sweetened beverages had the highest triglyceride levels. Boys with the highest intake of sugar sweetened beverages had lowered levels of high density lipoprotein (HDL).
These results confirm other previous studies in that they implicate sugar sweetened beverages in the development of weight gain, obesity, type 2 diabetes and cardiovascular disease. This was an observational study and as such cause and effect cannot be ascribed using this data in isolation. However, detailed metabolic studies looking at the effects of fructose have elucidated the mechanisms by which sugar sweetened beverages can cause these changes and the weight of evidence suggests that high intakes of sugar (sucrose) and fructose are drivers of disease. Interestingly, the boys with the highest intake of sugar sweetened beverages also had the highest fasting triglyceride levels, which provides more evidence that sucrose and fructose are able to increase the de novo lipogenesis pathway and increase the synthesis of fatty acids (here). These fatty acids and other lipids accumulate in liver and skeletal muscle tissue where they interfere with the insulin signal cascade, and this is now thought to be the primary driver of weight gain.
Dr Robert Barrington’s Nutritional Recommendation: Consuming sucrose and fructose in high amounts is detrimental to the health. Fruit contains fibre, and this indigestible carbohydrate component is able to protect the body from the detrimental effects of the sugars in the fruit. However, removal of the fibre from fruit to create fruit juice creates a drink that is no different from an artificially created sugar sweetened beverage. High intakes of fruit juice have been shown to have the same detrimental effects as high intakes of sugar sweetened beverages.
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