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A handy guide to sugars. What are they, are they all the same, what can they cause and why are they added to food and drink?

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Last updated: May 2014

Sugars play a vital role in our diets as a source of energy. They occur naturally in many foods including fruit, vegetables and dairy products, and are also added to some processed foods. Despite having been used for centuries in foods to improve palatability, as a preservative and to enhance texture and colour, there is still much confusion about the different types of sugars. How much we should be eating? Are some better than others? This factsheet aims to answer those questions.


What are sugars?

Sugars are a type of carbohydrate. Sugars can be found naturally in foods like fruit, honey and milk. They can also be added to foods in various forms.

What are sugars?

They can be made from one single sugar molecule (monosaccharides), such as glucose or fructose, or from two sugars joined together (disaccharides), such as sucrose (standard table sugar), which is made of a glucose and fructose molecule joined together. Foods contain different types and different amounts of sugars, e.g. glucose and fructose in fruit and vegetables, lactose in milk and sucrose which is found in sugar beet (a vegetable) and sugar cane (a grass).

Monosaccharides (a single sugar unit) are the simplest form of sugars. The most common types in food are glucose and fructose, found in fruit and vegetables

Disaccharides (2 single sugar units joined together) are found in sucrose (made up of 1 glucose and 1 fructose) and lactose (made up of glucose and galactose) found in milk.

Are all sugars the same?

There is a perception that naturally occurring sugars found in foods are different to refined added sugars in terms of their nutritional value, their effect on health and the way they are utilised by the body.

In fact all sugars have the same nutritional value regardless of the source and provide the same amount of calories (4 kcal per gram). The body cannot distinguish between added sugars and naturally occurring sugars as structurally they are the same.

Foods and drinks that have had sugars added to them may in some cases be high in energy yet also have low nutritional value. When sugars are naturally occurring in foods such as in fruits, vegetables and milk they are typically accompanied by other nutrients such as vitamins, minerals and fibres. Overall, it is a how healthy the diet is that is important.

What is the maximum amount of sugars recommended for a healthy diet?

The current reference intake for total sugars is no more than 90g per day. The Department of Health’s Committee on the Medical Aspects of Food Policy (COMA) made a recommendation that no more than 11% of food energy (50g) should be from non-milk extrinsic sugars (NMES).

Extrinsic sugars are defined as total sugars which are not bound into a cellular structure, e.g. the lactose in milk.

Honey, fruit juices, table sugar and confectionery are also examples of foods containing extrinsic sugars, referred to as non-milk extrinsic sugars (NMES).

Can sugars make you overweight?

Like any nutrient, if consumed in excess, sugars can lead to weight gain. It is important to manage energy intake and follow a healthy balanced diet. Why people gain weight is complex and can be due to several factors. It is therefore unlikely that a single food or nutrient will be responsible for causing someone to gain weight.

It is often thought that consuming sugary drinks can contribute to weight gain. There is currently inconclusive evidence to support this. However, sugary drinks often provide empty calories, i.e. no other positive nutrients, and should be enjoyed occasionally as part of an overall healthy balanced diet.

Can sugars cause tooth decay?

Yes, sugars can cause tooth decay, but the issue is mainly the frequency rather than the total amount of sugars consumed. Fermentable carbohydrates can create acid which cause tooth decay. However regular brushing, gaps between meals and the use of water and toothpaste with added fluoride can all help to prevent this from happening.

Why are sugars added to food and drink?

Sugars may be used in food and drink to perform a variety of technological functions. They are a natural preservative that reduce water activity to prevent the growth of micro-organisms, thereby reducing food spoilage such as in jams.

Enhancing palatability Sugars are naturally sweet and therefore are often used to balance out flavours for example bitterness or sourness.
Texture Sugars increase the starch gelatinisation temperature which sets the ‘foam’ at a higher temperature, providing a lighter texture.
Colour Sugars caramelise under heat providing cooked food with desirable aromas and flavours.
Preservative Sugars are a natural preservative. Sugars are highly soluble and therefore reduce water activity which prevents the growth of undesirable micro-organisms, reducing food spoilage and extending shelf life of foods such as jam.
Processing Sugars are integral to the fermentation process in bread making, yogurt manufacturing and brewing. Enzymes break the starch down into sugars for the yeast to ferment.


What role do sugars have in these cupboard favourites?

Tomato sauceTomato sauce

Tomatoes are naturally acidic, so to balance the flavours and make the sauce palatable a small amount of sugar is added. You will see this on the label if you buy it in the shops but also in most recipe books if you are making it at home.




As well as sweetening, sugar has a variety of roles in cake baking including:

  • Structure: by interacting with starch and protein during baking
  • Texture: by absorbing water it inhibits the gluten development (so cookies, cakes, quick breads aren't tough)
  • Colour and aroma: under heat sugar caramelises and reacts with other ingredients, e.g. proteins (goes brown) to provide cooked and baked foods with desirable colour and flavour
  • Stabilisation: for example with beaten egg foams in meringue


Sugar is essential in jam making. When added to the fruit it breaks down the glucose and fructose under the acidic conditions stopping unwanted micro-organisms from growing. Sugar also helps to develop the flavour and texture of the jam


Beer and wine

Beer and wine

Sugars are essential in the fermentation of alcohol, i.e. the conversion of sugars to ethanol (alcohol) and the generation of carbon dioxide by yeasts. Natural sugars contained in grapes, grains, honey and fruits are used in the production of wine, beer and whisky, mead and ciders.


For more information on sugars:

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