- Complex carbohydrates take longer to break down into sugars so don’t affect blood sugar levels as much as simple carbohydrates, which lead to blood sugar spikes.
- All bodies need glucose to perform basic functions, so it’s present in our blood, but is also a byproduct of what we put in our mouths.
- Despite fructose’s lower immediate impact on blood sugar levels, too much of it can cause long-term negative effects.
- Like fructose, sucrose is broken down in the liver and carries a lot of the same issues.
- Enjoying your favourite treats isn’t off the cards as long as you plan properly and limit hidden sugars.
Reducing your sugar intake is probably the first point of action when you’re diagnosed with type 2 diabetes. And because the condition makes it hard for your body to manage blood sugar levels, an awareness of what sorts of foods contain sugar is key.
However, if you’ve ever seen a nutritional label, you’ll know that deciphering the jargon around sugars is not easy. Gram amounts of nutrients like carbohydrates, sugars, and starches on packaging don’t include what types of sugar they are, and whether they’re added or naturally occurring. And that’s before you try to digest the 60 names associated with added sugars. 
Rather than getting lost in the small print, understanding the types of sugar and how they affect your body is a good place to begin, especially if you’re at the start of your type 2 diabetes journey.
Broadly speaking, there are two different types of sugar we need to consider first: complex and simple carbohydrates. Complex carbohydrates are made of lots of simple sugars that are connected by chemical bonds. The more there are of these bonds, the more complex it is for the body to break down those sugars—and the less impact it has on blood sugar levels. Beans, nuts, vegetables, and whole grains are all gold-star complex carbohydrates.
Simple carbohydrates—aka sugars—are made up of two molecules called monosaccharides and disaccharides. These are digested quickly by the body, sending immediate bursts of energy into the bloodstream. This is no bad thing. Simple carbohydrates are a major source of energy, which we need to stay alive. But there’s a divide when it comes to naturally occurring simple carbohydrates vs those that are added to food and drink during manufacturing.
Now we’ve posed that split to you, let’s dig into the different types of sugar within these categories, and how they affect your body.
Different types of sugar
If you have diabetes, you’ll hear the word ‘glucose’ used a lot. That’s because it’s the main type of sugar in the blood. When the body doesn’t produce enough hormones like insulin to control blood glucose levels, issues arise and that’s where diabetes comes in. But without glucose, we’d cease to exist. It’s the body’s preferred energy source and all our cells use it to power their various functions. Every second, the body burns eight billion billion molecules of glucose. Or in other words, if each glucose molecule were a grain of sand, you’d burn through every grain of sand on all the beaches across the globe every 10 minutes. So we need it, and we need it badly.
Luckily, lots of what we eat—carbohydrates, starch, and fibre—all eventually break down into glucose. If you eat a slice of white bread, for example, the starch is already being broken down as you chew. Chew long enough and it will start to taste sweet—that’s glucose. Enzymes also work on breaking molecules down into simple sugars in your small intestine and then it’s absorbed directly into your bloodstream.
Because glucose—a monosaccharide—is already in its simplest form, it doesn’t need to be broken down before your body can make use of it. Glucose is one of the fastest monosaccharides to be absorbed into the bloodstream, which means blood sugar levels rise more quickly when we eat foods containing it—they might even spike. Consuming high sugar, simple carbohydrate foods like fizzy drinks, fast food, and shop-bought sauces can send blood sugar levels soaring.
Fructose is a monosaccharide like glucose, but it behaves and affects the body in slightly different ways. It’s in every food that labels ‘sugar’ as an ingredient, as well as in fruit, fruit juices, and pretty much every other sweetener (think high fructose corn syrup, maple syrup, honey, white sugar, brown sugar…any of the 60 mentioned earlier actually!) Foods containing fructose may taste the sweetest but they have a comparatively low impact on your blood sugar levels. It’s absorbed directly into your bloodstream from the small intestine, like glucose, but fructose raises your blood sugar levels more gradually. 
Despite the lower immediate impact on blood sugar levels, too much fructose can cause long-term negative effects. Excessive consumption of processed sugar will send fructose overspill to the liver. Instead of breaking down fructose as a carbohydrate, it’s converted into fat, which is stored in the liver. It’s because of this fat storage in the liver that fructose is particularly dangerous, beyond just leading to weight gain, it can cause non-alcoholic liver disease, as well as metabolic syndrome.
On a more day-to-day level, fructose drives up the hunger hormone ghrelin, which makes you feel less full after eating. Studies have also found that fructose activates a reward pathway in your brain that can lead to increased cravings for sugar. Taking all this into account, fructose is perceived to be the most harmful when consumed in excess, so understanding which foods contain added fructose, which has been known to increase the chance of developing type 2 diabetes, will help steer your food choices.
Excess fructose from added sugars is not good for anyone with type 2 diabetes, but fruit is an entirely different ball game. It doesn’t just provide refreshing hits of fructose, but has a low-calorie density and lots of fibre. In general, fruit is a minor source of fructose in the diet compared to added sugars, so definitely keep fruit as part of a balanced diet.
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When you combine glucose and fructose, you get sucrose, or table sugar (ie the ingredient on food labels called “sugar”). It comes as a crystallised white sugar and can be found in kitchen cupboards everywhere. Taste-wise, it’s sweeter than glucose, but not as sweet as fructose.
When you eat sucrose, it’s quickly broken down by digestive enzymes into single molecules of glucose and fructose to facilitate its absorption (sucrose is actually 50% glucose and 50% fructose). Once this happens, blood sugar levels rise and rise fast—studies have found that sucrose causes similar increases as glucose, but greater increases than fructose.
In one study, ingesting sucrose resulted in higher blood sugar readings than honey, which is why you’re better off adding honey as a sweetener to your food, over sprinkles of table sugar. Like fructose, sucrose is metabolised in the liver and carries a lot of the same issues.
Lactose is a naturally occurring sugar found in milk and dairy products like cow's milk, goat's milk, yoghurt, cheese, and ice cream. Dairy products are full of nutrients like potassium, magnesium, and calcium that can help control high blood pressure, which is commonly associated with type 2 diabetes. Dairy can also help protect against the development of type 2 diabetes—so we know that in general, it’s a healthy food group to factor into your diet. 
A disaccharide, like sucrose, lactose is made up of glucose and galactose (yes, that’s another form of sugar) which are broken down by enzymes into simple sugars, then absorbed into the bloodstream. Drinking a glass of whole milk (lactose in its purest form) will raise blood glucose levels, but the fat content will stop them from rising as quickly as skimmed, fat-free or sweetened milk. That said, higher-fat dairy products also come with more calories, so it’s important to find a balance and err on the side of moderation with sweetened dairy products like flavoured milk and yoghurts.
Hidden sugars and low-fat conundrums
So we know that these three main types of sugar come in three forms: natural (glucose, lactose and certain fructose), added (fructose and sucrose), and as a natural byproduct of digestion (glucose).
Enjoying your favourite treats isn’t off the cards as long as you plan properly and limit hidden sugars. Sugar is also hidden in many packaged foods, fast food meals, and supermarket staples like bread, cereals, canned goods, pasta sauce, margarine, ready-cook mixes, frozen dinners, and ketchup. Making fresh, DIY versions of these goodies, such as your own granola, is one approach to avoiding lurking sugars.
Sugar has recently replaced saturated fat as the nutritional enemy number one. But the irony is that processed low-fat foods, which were brought in when fat was perceived as the bad guy, are actually loaded with sugar. To mimic the texture and consistency of high-fat foods, they’re packed with sugars like fructose and sucrose, and other unhealthy ingredients. A 100g serving of non-fat frozen yoghurt, for example, can contain as much as 21g of sugar, which is the same amount as in the same serving of regular vanilla ice cream.[14,15]
The optimal approach is eating lots of unprocessed whole foods, with minimal chance for added or hidden sugars. As you can see, a totally sugar-free diet is almost impossible, because almost all the foods we eat contain small amounts of it. Plus, what’s life without the occasional delicious sweet thing? As always, arming yourself with facts, such as how different sugars affect your body, is the best approach to adapting to life with type 2 diabetes.
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 L Teff, K., Elliott, S., Tschöp, M., et al. (2004). Dietary fructose reduces circulating insulin and leptin, attenuates postprandial suppression of ghrelin, and increases triglycerides in women. J Clin Endocrinol Metab 89 (6) P 2963-72. Accessible here.
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 Ice Cream, Vanilla. FoodData Central, U.S. Department of Agriculture. Retrieved 22 July. Accessible here.