Sugar consumption is associated with a significantly increased risk of many Western lifestyle diseases. In particular, high intakes of refined crystalline sugar can increase the risk of cardiovascular disease, type 2 diabetes, cancer and dental caries. However, it is obesity that is currently in the spotlight with regards to sugar consumption. Sugar is chemically sucrose, a disaccharide composed of a glucose moiety glycosidically bonded to a fructose moiety. It is the fructose component of sugar that is thought to be particularly detrimental to the health because animals and human studies show that when consumed in the absence of fibre and in high concentrations, it can lead to the development of insulin resistance within a few weeks. Sugar appears to be particularly detrimental when consumed in fruit juices or soft drinks, as the energy from the fructose is particularly quickly absorbed, which causes metabolic shifts in the liver that are a driver of insulin resistance.
Because of the possible detrimental health effects of the soluble sugars in soft drinks, researchers have investigated the contents of such drinks through chemical analysis. Sixteen soft drinks (including popular brands such as Pepsi Cola, Coca-Cola and Fanta) were analysed in one study1, to determine their sugar contents. The most common sugars in the 16 drinks were glucose, fructose and sucrose. However, interestingly, the amount of these sugars varied between different drinks of the same brand. The authors suggested that this was due to the hydrolytic degradation of the sucrose in the acidic medium of the drinks during storage. In other words, long term storage of the drinks causes more of the sucrose contained within the solution to be broken down to the monosaccharides fructose and glucose. Older drinks that have been on the shelf for a long time therefore have higher concentrations of fructose and glucose compared to more recently manufactured drinks, which contain more sucrose.
The authors commented that the sugar content of the drinks was worryingly high. In fact the sugar content was as high as 10 to 13 grams of sugar per 100 mL for the majority of drinks tested. This means that a typical can of soft drinks can contain upward of 35 grams of total sugars. This sort of intake of sugar, from a fibre-less, nutrient poor solution is evidenced to be rapidly absorbed and it then passes to the liver, which shifts it metabolism to the synthesis of fatty acids through the de novo lipogenesis pathway. The resultant fatty acids accumulate in tissues including the skeletal muscles and liver where they interfere with the insulin signal cascade and cause insulin resistance. This raises the fasting levels of insulin, which shifts the metabolism of the body as a whole to anabolism, through inhibition of catabolic pathways. This results in body fat accumulation, weight gain, obesity and all of its associated secondary diseases. A slow walk to the grave indeed.
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