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Dietary sugars: Cutting through the confusion

Updated: Aug 5, 2020

If you feel confused or overwhelmed as soon as someone starts talking about sugar, don't worry, you are not alone. Headlines are often written to grab our attention "a blueberry muffin could have a day's worth of sugar" and information can be contradictory or oversimplified (1). But once you break the science down into bite size chunks, the topic of dietary sugars becomes much more manageable.

Sugar is a broad term, used to describe carbohydrate molecules of a certain size and structure. There are two sub-groups of sugars: · Monosaccharides (glucose, galactose and fructose) · Disaccharides (sucrose, lactose and trehalose) (2).

Sugar can occur naturally in foods and drinks (for example, fruit contains glucose and fructose and milk contains lactose), or it can be added during manufacturing and/or preparation (for example, sugar in your favourite breakfast cereal or sugar added to your cup of tea). When we talk about reducing sugar in our diet, we are normally referring to 'free sugars' (often called added sugars) (3).

What are free sugars?

· All sugars added to foods and drinks · All sugars naturally present in fruit and vegetable juices, smoothies, purees etc (this might seem confusing, however, when we juice/blend fruits and vegetables, it releases the sugars from the cellular structure of the food and they become free sugars) · All sugars in drinks (the only exception is milk and dairy drinks)

For more detail, see the table below (4).

Why should we limit free sugars?

There is room in a healthy, balanced diet for sugary foods, however, excess sugar consumption has been linked to an increased risk of obesity, associated comorbidities such as (type 2 diabetes) and tooth decay (4).

How much free sugar should we be consuming?

The government recommends that no more than 5% of our daily energy (aka our daily calories) comes from free sugars. Furthermore, they recommend that we limit our consumption of sugary drinks.

Where we reduce free sugars in our diet, we should replace them with starchy foods (such as wholegrain pasta, rice, potatoes etc), naturally occurring sugars (from fruits and vegetables) and (for those that consume dairy) milk and milk products (4).

How do we know how much free sugar we are consuming?

We can start by quantifying the governments recommendations. For the average adult, this equates to no more than 30g (7 teaspoons) of free sugars per day (5).

Great! So we can add up the sugar on food and drink labels and make sure we don't exceed 30g?! Unfortunately not. By law, food and drink manufacturers must display 'total sugars' which includes naturally occurring sugars and free sugars. This can make it difficult to know how much free sugar is in a product, however, to get an idea we can check the ingredients. Let me explain..

Earlier, we discussed that lactose (a sugar) is naturally found in milk. If we look at a bottle of semi-skimmed milk, we can see that there are 4.8g of sugar per 100ml. However, by checking the ingredients ("ingredients: pasteurised homogenised semi-skimmed milk"), we can see there are no added sugars, therefore, we know that these are naturally occurring sugars. This is a simple example, however, we can apply the same logic to other products to get an idea of how much free sugar they contain.

In some foods (including sugary drinks, cakes, biscuits and pastries) all sugars are likely to be free sugars. However, other foods (such as pasta sauce) will likely contain both naturally occurring sugars (from tomatoes) and free sugars (sugar added by the manufacturer). In these situations, we won't be able to tell exactly what proportion of the sugars are free sugars.

So what can we do in these situations?

We can also look at 'traffic light labels'. Many foods and drinks have these labels which display nutrition information for energy, fat, saturated fat, sugars and salt (6).

These labels also display the nutrients as a percentage, for example, the label above indicates that a 150g serving contains 34g of sugar, which is 38% of the reference intake (the reference intake is the maximum amount of sugar that an average adult should be consuming per day to maintain a healthy, balanced diet).

If a product doesn't have a traffic light label, you can use the following guidelines to identify products that are low in sugar: · Low sugar products: 5g (or less) of total sugars per 100g · Medium sugar products: between 5 and 22.5g of total sugars per 100g · High sugar products: 22.5g (or more) of total sugars per 100g

Furthermore, it is worth noting that ingredients are listed in order of weight, so if sugar is right at the start of an ingredients list, we know that it is the predominant ingredient in that product (7).

Will free sugars always be listed as 'sugar' in the ingredients list?

No, there are other words and terms to look out for, but don't worry, you can use the list below to identify free sugars in the products you buy (8) · Sugar, cane sugar and brown sugar · Honey · Dextrose, fructose, sucrose, glucose and maltose · Isoglucose · Crystalline sucrose · High-fructose corn syrup · Corn syrup · Fruit juice concentrate · Molasses · Nectars

So there you have it, a brief overview of dietary sugars. There is still a lot of work to be done within society and the food and drink industries to make it easier for the population to become healthier (for example, clear and consistent food labels!). However, we have already made significant progress and it seems with the recent announcement of the government's obesity strategy there is more progress on the horizon (9). In the mean time, try not to get too bogged down by the numbers and remember that the main things to focus on are opting for 'high sugar' products less often and in smaller amounts and above all, consuming a healthy, balanced diet with plenty of variety.

Thanks to guest writer Heather Dolan for this week's blog. Heather has a BSc in Biological Sciences and an MSc in Human Nutrition. After completing her biology degree, she spent several years working (including a role in the pharmaceutical industry and an international internship with The Walt Disney Company), before she figured out that her passion lies in nutrition. Heather is now an AfN Registered Associate Nutritionist, "I am ready to start my nutrition career and see what exciting opportunities arise!"

You can find Heather over on instagram @nutrition.hd where she shares evidence-based nutrition information, nutrition drawings, recipes and meal ideas.


1. Muffin a day 'can take entire sugar limit' [Internet]. BBC News. 2018. Available from:

2. World Health Organization and the Food and Agriculture Organization of the United Nations. Carbohydrates in human nutrition [Internet]. Rome; 1998 p. 1-140. Available from:

3. The Scientific Advisory Committee on Nutrition. Carbohydrates and Health [Internet]. TSO (The Stationery Office); 2015 p. 1-384. Available from:

4. Swan G, Powell N, Knowles B, Bush M, Levy L. A definition of free sugars for the UK. Public Health Nutrition [Internet]. 2018;21(9):1636-1638. Available from:

5. Public Health England. Sugar Reduction: the evidence for action [Internet]. London: Public Health England; 2015 p. 1-48. Available from:

6. Looking at labels [Internet]. 2018. Available from:

7. How to cut down on sugar in your diet [Internet]. 2018. Available from:

8. Exploring sugars in the foods we buy FAQ [Internet]. British Nutrition Foundation; 2015. Available from:

9. Department of Health & Social Care. Tackling obesity: empowering adults and children to live healthier lives [Internet]. Department of Health & Social Care; 2020. Available from:

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