Natural sugars vs. processed sugars: what’s the difference?

How the body processes sugars: digestion, absorption, and blood glucose

Digestion starts in the mouth, where chewing breaks food into smaller pieces. Saliva contains enzymes that begin to split some carbohydrates. Most sugar digestion happens in the small intestine. Enzymes on the intestinal lining break complex carbohydrates into simple sugars, mainly glucose, fructose, and galactose.

Absorption follows quickly. The small intestine moves glucose and galactose into the bloodstream using active transport (a process that uses energy). Fructose uses facilitated transport, which relies on carrier proteins. The liver then converts much of the fructose into other compounds, including glucose, glycogen (stored carbohydrate), or fats, depending on energy needs.

Blood glucose refers to the amount of glucose circulating in the blood. After a meal, blood glucose rises. The pancreas responds by releasing insulin, a hormone that helps cells take up glucose for energy or storage. When blood glucose falls between meals, the pancreas releases glucagon, which signals the liver to release stored glucose.

• Food form matters: Whole foods that contain fibre, such as fruit, tend to slow digestion and absorption, which can reduce sharp rises in blood glucose.
• Liquid sugars absorb faster: Sugary drinks often pass through the stomach quickly and can raise blood glucose more rapidly than solid foods.
• Mixed meals change the response: Protein and fats slow stomach emptying, which can blunt and spread out the blood glucose rise.

People often describe these effects using the glycaemic index (GI), which ranks carbohydrate foods by how quickly they raise blood glucose. GI does not capture portion size, so glycaemic load (GL) can offer a more practical view. For clear definitions and examples, see the Diabetes UK guidance on carbohydrate and blood glucose.

What counts as natural sugars: fruit, vegetables, and dairy sources

Natural sugars occur within whole foods and arrive with nutrients that support health. Fruit contains fructose, yet fruit also provides fibre, water, vitamins, and plant compounds. Fibre slows eating speed and helps people feel full, which can reduce the chance of consuming excess energy. Whole fruit also tends to have a lower energy density than many sweet snacks, even when the fruit tastes very sweet.

Vegetables contain smaller amounts of natural sugars, mainly glucose and fructose. Root vegetables such as carrots and beetroot taste sweeter because starches convert to sugars as the vegetables grow and cook. Even so, vegetables supply fibre and key micronutrients, so the sugars come as part of a balanced package.

Dairy foods contribute lactose, a natural sugar made of glucose and galactose. Milk, yoghurt, and kefir also provide protein, calcium, iodine, and other nutrients. Choose plain yoghurt where possible, since many flavoured products include added sugars that change the nutrition profile. For clear definitions of “free sugars” and how they differ from sugars in intact fruit and milk, consult NHS guidance on sugar.

What counts as processed sugars: added sugars and refined sweeteners

Processed sugars usually refer to sugars and sweeteners that manufacturers add to foods and drinks during production, cooking, or at the table. People often call these added sugars. Common examples include sucrose (table sugar), glucose syrup, high-fructose corn syrup, honey, and fruit juice concentrates when used as sweetening ingredients rather than as whole foods.

Refined sweeteners start with a natural source, such as sugar cane, sugar beet, or maize, yet processing removes much of the original plant material. That refining produces a concentrated ingredient that adds sweetness and energy with few accompanying nutrients. As a result, products with added sugars can deliver a high sugar load in a small portion, which makes it easier to consume more energy than intended.

Food labels can help identify processed sugars. In the United Kingdom, the term “of which sugars” includes both naturally occurring and added sugars, so checking the ingredients list matters. Guidance from the NHS and the Scientific Advisory Committee on Nutrition (SACN) focuses on limiting free sugars, which include added sugars plus sugars in honey, syrups, and fruit juices.

Key nutritional differences: fibre, micronutrients, and food matrix effects

Natural sugars in whole foods usually arrive with fibre, micronutrients, and a supportive food matrix. Fibre, found in fruit, vegetables, pulses, and wholegrains, slows gastric emptying and reduces the speed at which sugars reach the bloodstream. That effect can blunt sharp rises in blood glucose and insulin, while also improving satiety. Processed sugars often appear in foods with little or no fibre, so the same amount of sugar can have a faster metabolic impact.

Micronutrients also differ. Whole foods that contain natural sugars can provide vitamin C, potassium, folate, calcium, or iodine, depending on the source. These nutrients support normal metabolism and tissue function, yet refined sugars contribute energy with minimal vitamins and minerals. Public health guidance reflects this contrast; the NHS advises limiting free sugars while choosing nutrient-rich foods.

The food matrix describes how nutrients and physical structure interact within a food. Intact plant cell walls, water content, and the presence of protein or fat can slow eating rate and digestion. For example, whole fruit tends to release sugars more gradually than fruit juice, even when the sugar content looks similar on paper. Texture and chewing also influence appetite signals, which can affect total energy intake across the day.

Health effects linked to high added sugar intake: weight, teeth, and metabolic risk

High intakes of added sugars can harm health, especially when sugary foods and drinks replace more nourishing options. Added sugars raise energy intake without providing fibre, protein, or many micronutrients, which can make it easier to consume more kilojoules than the body needs.

• Weight gain: Sugar-sweetened drinks and energy-dense snacks add kilojoules quickly and do not satisfy hunger as well as whole foods. Regular excess intake can lead to gradual weight gain.
• Dental caries (tooth decay): Oral bacteria ferment sugars and produce acids that erode tooth enamel. Frequent sugary snacks and drinks increase the time teeth spend in an acidic environment. Guidance from the NHS highlights that both amount and frequency matter for decay risk.
• Metabolic risk: Diets high in added sugars can worsen cardiometabolic markers in some people, particularly when they increase total energy intake. Sugary drinks can contribute to higher triglycerides and fatty liver risk in susceptible individuals.

Public health bodies set clear limits because these effects appear most consistently at higher intakes. The World Health Organization advises keeping “free sugars” below 10% of total energy, with extra benefits below 5%. Free sugars include added sugars plus sugars naturally present in honey, syrups, and fruit juices.

Context also matters. Whole fruit contains sugars, yet fibre and water slow eating and support fullness, which helps many people regulate intake. In contrast, added sugars often appear in foods that people consume quickly and in large portions. Reducing sugary drinks, limiting sweet snacks between meals, and choosing less sweetened versions of everyday foods can lower added sugar intake without removing naturally sweet whole foods.

How to spot added sugars on food labels: names, ingredients, and claims

Food labels can make added sugars hard to spot because manufacturers use many names and place sweeteners in different parts of the ingredients list. A practical approach is to check three areas: the ingredients list, the nutrition table, and any front-of-pack claims.

Check the ingredients list for common sugar names

In the United Kingdom, ingredients appear in descending order by weight. If a sugar or sweetener sits near the start, the product likely contains a meaningful amount. Watch for multiple sugar sources listed separately, since splitting them can make each one appear lower down the list.

• Table and “free” sugars: sugar, sucrose, dextrose, glucose, fructose, maltose, lactose.
• Syrups: glucose syrup, fructose-glucose syrup, glucose-fructose syrup, malt syrup, rice syrup, golden syrup, treacle.
• Concentrated fruit ingredients used as sweeteners: fruit juice concentrate, concentrated grape juice, fruit purée concentrate.
• Other sweetening ingredients: honey, agave nectar, maple syrup, molasses.

Some products also use non-sugar sweeteners (such as aspartame or sucralose). Those ingredients can reduce sugar content, yet they still keep a sweet taste. People with phenylketonuria must avoid aspartame because it contains phenylalanine.

Use the nutrition table to compare products

The nutrition table lists “carbohydrate” and “of which sugars” per 100 g or 100 ml. That sugars figure includes both naturally occurring sugars and added sugars, so it does not confirm the source on its own. Even so, it helps when comparing similar items. For example, choose the option with lower sugars per 100 g when comparing two flavoured yoghurts, then confirm the source in the ingredients list.

For context on daily limits, the NHS guidance on sugar explains recommended maximum intakes of free sugars.

Interpret common label claims with care

Marketing terms can sound reassuring, yet they often leave room for added sugars.

• “No added sugar”: the manufacturer has not added sugars, honey, syrups, or juice concentrates. The product can still contain natural sugars, and it may taste sweet due to sweeteners.
• “Unsweetened”: no sweetening ingredients, yet naturally occurring sugars may remain (for example, in milk).
• “Made with fruit” or “contains fruit juice”: fruit ingredients can still raise sugar content, especially when used as concentrates.

When in doubt, prioritise minimally processed foods and use the ingredients list as the deciding tool.

Practical swaps to reduce processed sugars without losing flavour

Reduce processed sugars by changing where sweetness comes from, rather than removing it. Swap flavoured yoghurt for plain yoghurt and add berries, grated apple, or cinnamon; the fruit adds sweetness with fibre and water. Choose porridge oats instead of sweetened cereals, then use mashed banana or a small handful of raisins for flavour. Replace sugary drinks with sparkling water plus lemon, lime, or mint, or select an unsweetened tea or coffee and add vanilla or spices instead of syrup.

When baking, cut the sugar in a recipe by about one third and increase flavour with citrus zest, cocoa, or ginger. For snacks, pick nuts with a piece of fruit instead of biscuits, or spread peanut butter on wholegrain toast rather than jam. To guide choices, compare products using the nutrition label and aim for lower “of which sugars” per 100 g, using NHS label advice.

Common myths and misconceptions about natural and processed sugars

Many people assume that “natural” automatically means “healthy”, yet sugar still counts as sugar once the body absorbs it. A glass of fruit juice can deliver a similar sugar load to a soft drink, even though the sugar started in fruit. The key difference sits in the form of the food: whole fruit brings fibre and structure, while juice removes much of that structure and makes it easier to consume more quickly.

Another common myth claims that brown sugar, coconut sugar, agave, maple syrup, and honey are “better” than white sugar. These sweeteners may contain trace minerals, but the amounts remain too small to offset the effect of frequent, high intakes. For most people, the practical impact on blood glucose and dental health stays similar when portions match.

Some also believe that “sugar-free” always means low sugar. Products can still contain naturally occurring sugars (such as lactose in dairy) or use sweeteners that maintain a preference for very sweet tastes. For clear guidance, rely on the ingredients list and nutrition information, and follow advice from the NHS on limiting free sugars.