Breaking Down Sugars and Sweeteners

Sweeteners are regularly used by those looking to reduce their sugar intake. But, how do sweeteners affect our body?

Sweeteners can create the same sweet taste many of us love, giving us the experience of eating sweet foods with much fewer calories. But how do sweeteners achieve the same effect as sugar so lightly, and do they affect our bodies differently than sugar? 

Why Are Sweeteners So Low-Calorie?

Sugars like sucrose (aka table sugar) bind to the ‘sweet’ taste buds on our tongue, activating them and sending signals to the brain - which we experience as a sweet taste.¹ Sweeteners bind to these same taste buds far more effectively, meaning sweeteners can taste much sweeter to us than sucrose in much smaller amounts.¹ For example, aspartame (a common ingredient in diet sodas) tastes up to 200 times sweeter than table sugar!

This means we can re-create the same sweetness in our food by replacing lots of sugar with a tiny amount of sweetener, reducing the number of calories we add. In addition, some sweeteners can’t be digested by our bodies, meaning even the small amount of calories they carry pass through our bodies without being absorbed. 

How Our Body Breaks Down Sugars and Sweeteners 

Sweeteners have different chemical structures to table sugar. Despite similar effects on our taste buds, they aren’t broken down, digested or absorbed in quite the same way as sugars by our bodies. 

How sugars are digested and stored

Different types of sugar impact and are stored in our bodies in different ways. Sucrose, for example, is made of two sugar molecules: fructose and glucose. Fructose is sent to the liver to be broken down,² while glucose is the sugar molecule our body immediately uses for energy. Glucose is released from foods during digestion, raising blood glucose levels before it is absorbed by our cells or stored as glycogen in the liver or muscles. 

How sweeteners are digested and stored

In most cases, because sweeteners are consumed in such small amounts, they have a minimal impact (if any) on blood glucose levels. In other cases, sweeteners like aspartame - commonly used in diet sodas - don’t cause blood glucose levels to rise because they’re made of amino acids (the building blocks of proteins), and so don’t release any glucose when broken down. Finally, some sweeteners may remain undigested and unabsorbed, therefore failing to raise blood glucose at all. This makes sweeteners attractive to people who are watching their sugar intake - they can enjoy sweet tastes without the risk of high glucose intake. 

Sweeteners Impact On Our Gut

The sugars and sweeteners in our diet can also impact our gut.³ For example, certain sweeteners like xylitol (commonly added to chewing gum) may cause laxative effects. This is because xylitol is a polyol,⁴ or sugar alcohol molecule, that is difficult for our bodies to digest. When sweeteners like xylitol move into our gut and remain undigested, the increased concentration of sweeteners in the gut drives water to move into the gut via osmosis. With more water drawn into the gut, this may result in diarrhoea. 

The Effects Of Sugars And Sweeteners On Hunger

Replacing sugar with sweeteners can also change how satisfying we find sweet treats. As we digest and absorb sugar, our blood sugar levels rise, which drives changes in the levels of hormones in our blood that regulate how hungry we feel. 

For example, after we eat, our raised blood sugar levels cause our pancreas to increase its secretion of insulin (which contributes to feeling full) and decrease the secretion of the hormones ghrelin and glucagon (which drive appetite). 

While some sweeteners, such as oligofructose, appear to cause the same hormonal responses from the pancreas and can quench our hunger,^5,6 other sweeteners do not. Some sweeteners do not initiate the same response associated with feeling full because they either remain undigested or don’t contain glucose to cause the hormonal response from this spike. As well as raising blood sugar slightly, animal studies have shown that sweeteners like sucralose drive an increase in ghrelin secretion, which increases appetite despite the consumption of sweetened foods.⁵ 

Read more about the issues with scientific research into the health impacts of sugars and sweeteners.

Replacing Sugar with Sweeteners 

For people monitoring their blood sugar, including diabetic patients, sweeteners are a way to keep enjoying the taste of sweet foods without ingesting large amounts of sugar.  However, if the sweet taste of sweeteners is coupled with a failure to drive hormonal responses that leave us satisfied, they may leave us craving more, even sweeter foods after a meal. Replacing sugar with sweeteners isn’t a ‘quick fix’ solution for everyone.