Why the sugar number on the back of the packet tells you less than you think, and a lot less than companies want you to know.
Pick up almost any packaged food and turn it over. In the nutrition panel, under carbohydrates, you will find a line that reads: of which sugars. That number is the one that gets quoted in articles, cited by parents, used in marketing comparisons, and turned into traffic light labels on the front of the pack.
It is also, in an important sense, the wrong number.
The figure on the label is total sugars. It includes every sugar present in the food, regardless of whether it comes from added sweeteners or from naturally occurring sources like milk and whole fruit. Free sugars, the category that actually drives the health concern, can be substantially different. And the food industry, entirely legally and with no obligation to do otherwise, presents the larger number.
Understanding the difference matters. For adults making their own dietary choices, it gives a more accurate picture. For parents trying to navigate food choices for children, it is one of the most practically useful things to know.
Free sugars are defined by the World Health Organisation and adopted by NHS and SACN guidance in the UK as any sugar that has been added to a food or drink, plus the sugars naturally present in honey, syrups, and unsweetened fruit and vegetable juices. They are called free because they are not bound within the cellular structure of a whole food.
Free sugars are the target of public health limits. The NHS recommends that adults consume no more than 30g of free sugar per day. For children aged 7 to 10, the limit is 24g. For children aged 4 to 6, it is 19g. These are the numbers that matter when it comes to dental health, blood glucose management, weight, and metabolic health.
What free sugars do not include: the natural sugars in whole fruit, vegetables, and dairy. When you eat an apple, the sugar is trapped inside intact fruit cells. Your body digests it more slowly, it comes packaged with fibre, water, vitamins, and phytonutrients, and it does not produce the same blood glucose response or dental impact as equivalent free sugar. The same applies to lactose in milk and plain yoghurt. These are not the problem.
The problem is sugar that has been removed from its original context, whether by juice extraction, processing, or deliberate addition, and placed into a product in a form the body treats very differently.
UK food labelling law requires the declaration of total sugars. This is the sum of all sugars present, whether added or naturally occurring, free or bound. It is a precise and accurate measurement. It is also a less useful one for the purposes of understanding how much free sugar a product contains.
The practical difference can be significant. A 125g pot of plain full-fat yoghurt might show 6g of sugar on the label. That is almost entirely lactose, a naturally occurring milk sugar that does not count as a free sugar and is not subject to the daily limit. A 125g flavoured yoghurt might show 15g of sugar. Some of that will be lactose, some of it added free sugar. The label does not separate them.
A glass of orange juice can show 20g of sugar on the label. Whole oranges contain roughly the same amount of sugar, but the juice version counts as free sugar because the fibre structure has been broken down and the sugars are now free. The label number looks identical, the health implication is meaningfully different.
Daily free sugar limits for children are considerably lower than for adults, and considerably more frequently exceeded. A child aged 4 to 6 has a daily free sugar limit of 19g. A single 330ml can of Coca-Cola contains 35g. One standard Mars bar contains 31g. A small pot of flavoured yoghurt marketed directly at children can contain 11 to 14g of free sugar. A glass of fruit juice at breakfast adds another 15 to 20g.
This is not particularly unusual eating for a child. And yet before lunch, the daily limit has often already been exceeded, sometimes by a significant margin, using foods that carry nutritional claims, bright packaging, and in some cases the word natural prominently on the front.
The total sugars figure does not help here. If a parent sees 14g of sugar on a flavoured yoghurt and 11g on a whole apple, the numbers look comparable. They are not. The apple contributes zero free sugar. The yoghurt may contribute 8 to 10g. The total sugars line obscures that distinction completely.
The food industry is not required to declare free sugars separately on UK labels. It is required to declare total sugars. This is not an oversight. The total sugars figure is consistently higher than the free sugars figure for any product containing dairy or whole fruit ingredients, which makes the comparison with guideline limits look more favourable.
Front-of-pack traffic light labels use the same total sugars figure. A product can display an amber or even green traffic light for sugars while containing a substantial amount of free sugar, because the reference the label is compared against is the adult total sugars reference intake of 90g, not the free sugar limit of 30g. The distinction between these two figures is never explained on the packaging.
Portion sizes are another mechanism. A serving declared on the pack may be smaller than the amount most people actually eat. A 25g portion of cereal may show 3g of total sugars. The bowl most people pour contains 50 to 60g of cereal. The label invites the smaller number without making the multiplication easy to do.
Natural is not regulated in UK food law in a way that limits how it can be applied to high-sugar products. Products containing added fruit juice concentrate, dried fruit, or agave syrup can carry natural labelling. These are all free sugars.
Fruit juice is one of the most significant sources of free sugar in the UK diet, particularly for children, because it carries a nutritional halo built on its whole fruit origins. But the juice extraction process breaks down the cell walls that trap sugar in whole fruit, liberating the sugar into a free form. A 200ml glass of orange juice contains around 18 to 20g of free sugar, equivalent to more than four teaspoons, comparable in free sugar terms to a small can of fizzy drink.
Smoothies blended from whole fruit are slightly better because they retain some of the fibre structure, but once fruit is blended, much of the cell wall integrity is lost and the sugar is considered free under SACN guidance. The guidance counts juice and smoothies toward the daily free sugar limit regardless of how they are marketed.
Plain yoghurt contains lactose, a naturally occurring milk sugar that does not count as free sugar. Flavoured yoghurts contain added sugar in addition to lactose. The label does not separate the two. A flavoured yoghurt showing 14g of total sugars might contain 6g of lactose and 8g of added free sugar. Or 4g of lactose and 10g of added free sugar. The label cannot tell you which.
Children's yoghurt products are frequently positioned as healthy, calcium-rich foods. Some are. But the free sugar content in flavoured varieties marketed at children can be substantial relative to a child's daily limit, and the total sugars figure on the label systematically understates this by including the lactose.
Several mainstream breakfast cereals contain between 25 and 35g of total sugars per 100g, almost all of it free sugar. But the declared sugar figure is based on a 30 to 40g portion, making the per-serving number look small. And cereals eaten with milk then display a combined total sugars figure that includes the milk lactose, which can make the comparison to limits look more favourable than the cereal's own contribution warrants.
A bowl of a higher-sugar cereal with 200ml of semi-skimmed milk might show 20 to 22g of total sugars. Of that, around 9 to 10g is milk lactose. The free sugar contribution from the cereal might be 10 to 12g, more than half the daily limit for a child aged 7 to 10, before anything else is eaten that day.
The cereal bar and snack bar category is one of the most misleading segments of the UK food market in terms of the gap between positioning and free sugar content. Many bars contain dates, dried fruit, fruit juice concentrate, honey, or agave as their primary sweetening ingredient. All of these are free sugars. Products containing them can carry clean label, no added sugar, and natural positioning while delivering 15 to 25g of free sugar per bar.
No added sugar means no refined sugar has been added. It does not mean the product is low in free sugar. Fruit juice concentrate, honey, and dried fruit all count as free sugar regardless of how natural their origins.
The ingredients list is more useful than the nutrition panel for understanding free sugar content. Ingredients are listed in order of weight. If sugar, glucose syrup, fructose, fruit juice concentrate, honey, agave, or dried fruit appear high on the list, the product's sugar content is predominantly free sugar. If the only sugars present are from dairy, the total sugars figure on the label is mostly lactose.
For juice and smoothies, the practical guideline from NHS is a maximum of 150ml per day as part of your five a day, because beyond that the free sugar contribution becomes significant. Whole fruit is preferable to juice for the same reason the fibre remains intact and the sugar remains bound.
When comparing products, compare them on free sugar content rather than total sugars where you can. For products without separate free sugar declarations, the ingredients list is your best tool. The further up the list sweetening ingredients appear, the higher the free sugar contribution relative to natural sources.
Free sugar raises different metabolic questions from naturally occurring sugar because of how rapidly it is absorbed, the effect it has on blood glucose and insulin response, and its role in dental decay. Bacteria in the mouth ferment free sugars to produce acids that attack tooth enamel. Naturally occurring sugars in whole fruit are less accessible to oral bacteria because they are still inside intact plant cells. The total sugars figure on a label does not capture this distinction.
For children, the dental health dimension is particularly significant. Dental caries is the most prevalent chronic disease in UK children. The mechanism is well-established and the primary dietary driver is free sugar frequency and quantity. A child consuming 40g of free sugar a day from juice, flavoured yoghurt, cereal, and snack bars is not getting that from the total sugars figure on any of those products without understanding the distinction.
This is not a problem that requires unusual diets or significant lifestyle changes to address. Understanding what the label is and is not telling you is the starting point. Making different choices based on free sugar content rather than total sugar content moves the needle substantially, without eliminating any food category or requiring extreme restriction.
Reference intakes on UK food labels are calculated for an adult consuming 2,000 kcal per day. The percentages shown for sugar, fat, and salt reflect adult intake targets. A product showing 8% of the reference intake for sugars looks low. For a child aged 4 to 6 with a free sugar limit of 19g, the same product might represent 30 to 40% of their actual daily limit.
This gap is largest for products where children are a significant part of the audience: flavoured yoghurts, breakfast cereals, fruit drinks, cereal bars, and snack products. The traffic light system and percentage reference intake are calibrated to adult thresholds. The marketing, the packaging design, the characters and colours and claims, are frequently aimed at children. The nutrition information required to understand what is actually in the product is written for adults.
There is no regulatory requirement to display child-specific reference intakes on packaging. There is no obligation to declare free sugars separately from total sugars. The information exists in public health guidance. It does not appear on the label in a form that helps the parent of a five-year-old at the supermarket make a more informed choice.
For guidance only. NHS and SACN free sugar recommendations as of 2025. Specific sugar figures cited in examples are derived from manufacturer nutrition panels and may vary by product variant or recipe update.
