What is Sugar?

See also: Complex Carbohydrates, Sugars and Diet

There has been a lot of media attention recently about sugar in our diets and its effect upon our health. However, there are so many different types, names and classifications of sugar that it can be hard to relate these claims to our own choices.

This page describes the different types of sugars and sweeteners.

Sugars is the name for a group of carbohydrates that have a short-chain, generally cyclic structure, and are sweet-tasting. However, several other substances can also be used to sweeten foods.

The simplest of all the sugars are called monosaccharides and these form the building blocks of the other types of carbohydrates. Although monosaccharides can be found on their own, they are more commonly found bonded in pairs to form the rest of the range of sugars. 

There are three common monosaccharides:


Known sometimes as dextrose, glucose is the primary energy source for most biological organisms.


Fructose, or fruit sugar, is the sweetest and most water soluble of all the sugars, being about 1.7 times sweeter than table sugar, and is found mainly in fruit.


Galactose does not commonly occur in its free source, but it can be found in peas and other legumes. It is less sweet than either glucose or fructose.

Most of the common sugars that we eat are known as disaccharides because they are a mixture of two of the monosaccharides above.

Factors like how sweet they are, how fast they get absorbed, and how they affect our bodies depend largely on which two are combined.

Common combinations of monosaccharides include:


The sugar that we use in our homes to add to drinks or for baking - whether granulated, caster (super fine), or icing (powered) sugar.

Sucrose is formed of glucose and fructose molecules combined.

Although sucrose is found in many plants, only sugar cane, grown in tropical climates, and sugar beet, grown in colder regions, contain sufficient quantities to make extraction viable.

Inverted Sugar

Inverted sugar is similar to sucrose, but while the glucose and fructose molecules are bound together in sucrose, they are both free in inverted sugar. 

This makes inverted sugar taste significantly sweeter than sucrose.

Golden Syrup, Treacle

These are a by-product of sugar refining and are a mixture of inverted sugar and sucrose.

Golden syrup is a thick, amber-coloured product, also known as light syrup, while treacle is darker and has a more distinct flavour.

Brown, Muscovado, Barbados, Molasses, Demerara, Turbinado Sugar

These sugars are all essentially the same as white sugar or sucrose, but are either less refined so that the molasses component of the sugar cane extract has not been entirely removed or refined white sugar with molasses added back in. 

They are all brown in colour and have a caramel flavour, the degree of both depending on how much molasses is in the final product. 

Nutritionally though, brown sugars have very little different from white sugar.


Lactose is the sugar found in milk.

Although all infant mammals can tolerate lactose, only humans carry this through to maturity.  Even so, this trait is genetic and varies between individuals and races and around 5% of  Northern Europeans and 90% of some African and Asian countries are lactose intolerant, suffering bloat and abdominal pain if they ingest milk or milk products.


Maltose is mostly found in germinating grain, particularly barley, and is less sweet than glucose, fructose and sucrose. 

Maltose consists of two glucose molecules bound together.

High Fructose Corn Syrup

High fructose corn syrup (HFCS) is a sugar replacement that is slightly sweeter than sucrose.

In Europe, HFCS is known as glucose-fructose syrup, fructose-glucose syrup or isoglucose.  It is an inverted sugar produced from corn or maize starch and, although the production process is quite lengthy, the sweetener is much cheaper to produce than regular sugar and is produced as a liquid, so is easier to blend with other foodstuffs.

HFCS is generally used in the HFCS55 form, containing 55% fructose and 45% glucose and is found extensively in processed foods and soft drinks in the US, although it is less widespread in Europe.

Natural Sweeteners

Natural sweeteners are sugar-based natural products used both for their sweetness and for their flavour.


Produced by bees, honey was probably the first substance to be added to other foods to make them sweeter.

The flavour of honey depends largely on the species of pollen collected by the bees.  In addition to being used as a sweetener, honey has antiseptic qualities.

Honey consists mainly of fructose and glucose

Maple Syrup

Maple syrup comes from the sap of a maple tree and is slightly less sweet and more runny than honey.

Maple syrup mainly consists of sucrose.

Rice Malt Syrup

Also known as brown rice syrup, rice malt syrup is made from fermented cooked rice and consists mainly of maltose and glucose.

Rice malt syrup is more calorific and less sweet than sugar and has been reputed to have higher than desirable arsenic levels.  It contains higher levels of maltose than fructose and glucose.

Agave Nectar

Agave nectar is made from the sap of the agave plant enzymatically processed into a syrup.   It is very high in fructose (approx. 85%) and therefore very sweet. It does not have an identifiable flavour like honey and maple syrup.

WARNING! Still sweet, still sugar

Many people believe that natural sweeteners must be better for you than “sugar”, because they are ‘natural’.

However, sugar is also natural – and most natural sweeteners, as we have seen, contain sugars of various kinds, in various quantities.

In terms of the effect on your metabolism, natural sweeteners are more or less exactly the same as any other sugar. They should therefore not be used as substitutes for refined sugar.

Non-Sugar Sweeteners

Sugars are not the only sweet tasting substances used in our food.  A number of other sweeteners are routinely used, and these can either be natural in origin, coming from plant extracts for example, or artificial, synthesized solely for their role as a sweetener.


An extract from the Stevia rebaudiana plant used to produce an artificial sweetener.

The sweetness is provided by a group of chemicals called glycosides, and is up to 150 times sweeter than sugar.

Different manufacturers extract and purify the stevia plant in different ways, which leads to slightly different products, some of which may have a pronounced and slightly bitter after taste.

Sugar Alcohols

Derived from plants, sugar alcohols are sweeteners that are related to sugars but have fewer calories because they are not fully metabolized.

As such they have less effect on blood sugar levels, but can have a laxative effect if taken in large amounts.  Sugar alcohols include Erythritol, Glycerol (also known as glycerin or glycerine), hydrogenated starch hydrolysates, isomalt, lactitol, maltitol, mannitol, sorbitol, xylitol.

Interestingly, sugar alcohols are often found in products labelled “sugar free” or “no added sugar”

Artificial Sweeteners

Artificial sweeteners are low or zero calorie products often used instead of sugar to sweeten foods and drinks.

Artificial sweeteners are not just used in so-called 'diet foods' since many regular ready-made meals and other products also contain artificial sweeteners.

Are Artificial Sweeteners Safe?

There has been much debate, research and controversy surrounding the safety of artificial sweeteners. The US National Cancer Institute and Cancer Research UK currently state that there is no evidence that artificial sweeteners cause cancer in humans, and they must all undergo rigorous testing before being licenced to be used in food.

However, you should stay up-to-date with current research into the health effects of artificial sweeteners and make your own decision as to which, if any, you wish to eat.


Aspartame is a low calorie artificial sweetener based on joining the protein amino acids aspartic acid and phenylalanine together.

Aspartame is one of the most common sweeteners and is sold under a variety of trade names including NutraSweet, Equal, Spoonful, Equal-Measure, Canderel, Benevia, AminoSweet and NatraTaste.

Aspartame has been the subject of a number of health scares, and has been linked with brain tumours, leukaemias, lymphomas, migraines and a number of other issues. However a number of reviews, for example by the US National Cancer Institute in 2006 and the European Food Safety Authority as recently as 2013, have found no evidence for this.

The acceptable daily intake, set at 100 times lower than the amount that might cause health concerns from laboratory studies, is 40mg per kilo of body weight.

For a 75kg/165lb adult, this equates to somewhere in the region of 19 cans of diet soda or 363 sweetener tablets a day.


Discovered in 1879, saccharin was the first artificial sweetener.

Sold as Sweet’N Low and Sucron, it is up to 300 times sweeter than sugar although some find it has a slightly bitter or metallic after taste.

Saccharin is used in products including foodstuffs, drinks, chewing gum, toothpaste, lip gloss and vitamins.

Saccharin was suspected of causing bladder cancer in the 1970s, but this has been disproved and a 1999 re-evaluation by the International Agency for Research on Cancer concluded that saccharin was not a possible human carcinogen.

The acceptable daily intake is 5mg per kilo of body weight.


Discovered in 1996, sucralose is much sweeter than both saccharin and aspartame and more heat stable.

Sucraloase is sold under the brand names Splenda Zerocal, Sukrana, SucraPlus, Candys, Cukren, and Nevella.

The acceptable daily intake is 15mg per kilo of body weight.

Acesulfame K

Acesulfame K is most often used blended with sucralose to decrease the bitter aftertaste of aspartame in a range of low-calorie foods and drinks.

The acceptable daily intake is 9mg per kilo of body weight.


Approved by the FDA in 2002 and made by NutraSweet, neotame is a derivative of aspartame.

Neotame is, however, much sweeter than aspartame and is therefore used at much lower levels.  As with all sweeteners, there is controversy over its safety. However, the consumer advocacy group Center for Science in the Public Interest has ranked neotame as “safe”.

Artificial sweeteners, diet products and weight-loss diets

Artificial sweeteners are often used in so-called ‘diet’ products, such as reduced-sugar fruit squashes and soft drinks. The idea behind their use is that they do not provide the same calories as sugar, so would not cause weight gain.

Unfortunately, the science is not that simple.

Studies have shown that when we eat or drink something that tastes sweet, our bodies prepare for sugar by releasing insulin. Sugars are rapidly removed from the blood into storage. This is good when we have eaten sugar, but not so good when we haven’t, because it can cause low blood sugar, and lead to us craving sweet food.

In other words, consuming ‘diet’ drinks and foods leads us to want to eat more, and especially sugars.

Studies suggest that consuming artificial sweeteners is linked to long-term weight gain, and may be associated with the so-called ‘obesity epidemic’.

To find out more about how sugar is metabolized by our bodies, and its effect on our health, continue to our Sugar and Diet page.