There remains considerable confusion in the media and debate among health professionals about sugar and risks of cancer but there really should not be – the evidence is very clear.
The misunderstanding arises mainly because most articles fail to emphasise that it’s not sugar itself that is bad, it’s the habit of eating or drinking processed sugar and refined carbohydrates that is unhealthy – a very big difference, which we will aim to explain.
Sugar itself does not cause or promote cancer, it helps to feeds every cell in the body, and is so important to the function of the brain and other organs that the body has several back up strategies to keep blood levels normal.
The carbohydrates we eat are broken down by our digestive and metabolic system to form simple sugars, such as glucose and fructose, to provide our cells with energy (other energy sources include fatty acids and ketones).
What is the glycemic index?
The habit of eating processed “added” sugar and, to lesser extent, processed carbohydrates, is harmful. These foods have a high glycaemic index (GI), which is a ranking of foods on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating.
Foods with a high GI are those that are rapidly digested and absorbed and cause a marked fluctuation in blood sugar levels. On the other hand, low GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels. Incidentally, some clinical papers refer to glycaemic load (GL) – this takes into account the amount as well as the type of food eaten.
The worst culprits are free simple sugars added to food, defined by the World Health Organisation (WHO) as foods with high capacity for increasing the GI but can also include carbohydrates and more complex sugars.
Other factors that influence GI include the timing and total content of the meal. Carbohydrates eaten alone will be absorbed quicker but eaten with fat, protein, and fibre slows gastric emptying. This allows for a more gradual release of carbohydrate in food into the body, with less of an impact on blood sugar levels.
Processed sugar, such as sweets on an empty stomach first thing in the morning, is particularly harmful as they are absorbed rapidly. Conversely, a small sweet treat after a healthy meal will have less of an impact as the stomach has a plenty of other food to slow the gut down. Likewise, eating the whole fruit will reduce the impact of the sugar in the juice as the pulp and fibre slow gastric emptying.