Sugar: The Complete Guide to Types, Effects and Reducing Your Intake

**Glucose** is the body's primary fuel. Every carbohydrate you eat is ultimately converted to glucose. It raises blood sugar (and consequently insulin) in proportion to the quantity consumed. Glycaemic index (GI) measures how quickly a food raises blood glucose relative to pure glucose.

**Fructose** occurs naturally in fruit, honey and some vegetables, and is used widely as high-fructose corn syrup (HFCS) in processed foods. Unlike glucose, fructose is metabolised primarily in the liver and does not directly raise blood insulin. However, excessive fructose (particularly from liquid sources) leads to de novo lipogenesis (fat production in the liver), elevated triglycerides, and has been linked to non-alcoholic fatty liver disease and visceral fat accumulation.

**Sucrose** (table sugar) is 50% glucose and 50% fructose. It behaves accordingly — providing both a blood glucose response and the metabolic fructose burden.

**Lactose** (milk sugar) is glucose + galactose. It has a relatively low GI (~46) and comes packaged with protein and calcium. The evidence does not support avoiding lactose-containing dairy on health grounds for those without lactose intolerance.

**Natural sugars in whole fruit vs. added sugars in processed food:** A can of soda (35g sugar) and a large apple (25g sugar) contain similar sugar quantities. The critical differences: the apple comes with 4–5g of fibre (which slows glucose absorption), water content (promotes satiety), vitamins, minerals and polyphenols. The fibre matrix of whole fruit fundamentally changes how its sugar is absorbed — making 'total sugar' a misleading metric when comparing whole foods with processed ones.

**Weight and obesity:** Added sugar — particularly from sugar-sweetened beverages (SSBs) — is consistently associated with weight gain in prospective studies and meta-analyses. SSBs are uniquely problematic: liquid calories don't trigger satiety signals in the way solid food does, meaning people don't compensate by eating less. A 2013 BMJ meta-analysis found that reducing SSB consumption was directly associated with reduced body weight.

**Type 2 diabetes:** Excessive added sugar intake, particularly from SSBs, independently increases type 2 diabetes risk — even controlling for body weight. This is thought to be via fructose's hepatic effects and the consequences of chronic insulin elevation.

**Cardiovascular disease:** A landmark 2014 JAMA study found that adults consuming ≥25% of calories from added sugar had more than double the risk of cardiovascular mortality compared to those consuming <10%. The effect was independent of total calorie intake.

**Dental health:** The most clearly established harm of sugar is dental caries. Bacteria in the mouth ferment sugar, producing acids that demineralise tooth enamel. Frequency of sugar exposure (snacking throughout the day) is more damaging than total quantity.

**Cancer:** Claims that 'sugar feeds cancer' in a uniquely harmful way are scientifically inaccurate. All cells — cancerous and healthy — use glucose. Reducing added sugar is sensible for weight management (excess weight is a significant cancer risk factor), but cutting sugar to 'starve' cancer is not supported by evidence.

**WHO recommendation:** Less than 10% of total energy from free sugars (added sugars plus sugars naturally present in honey, syrups and fruit juices). A further reduction to below 5% (about 25g or 6 teaspoons per day) is conditionally recommended for additional health benefits.

**American Heart Association:** No more than 25g (6 tsp) of added sugar per day for women; 36g (9 tsp) for men.

**Context:** The average adult in the UK and US consumes 60–90g of added sugar daily — far exceeding these guidelines. However, this is heavily skewed by high consumers. Approximately 20% of the population consumes very little added sugar and is at low risk.

**What 25g of added sugar looks like:** One can of regular cola (~35g) exceeds the daily limit on its own. A flavoured yoghurt (~15g) + a glass of orange juice (~20g) + a serving of breakfast cereal (~10g) totals 45g before any other food.

**Eliminate or significantly reduce SSBs first.** Sugar-sweetened beverages (sodas, fruit juices, energy drinks, sweetened coffees) are the single most impactful target. They provide large quantities of rapidly absorbed sugar with zero satiety benefit. Replacing SSBs with water, sparkling water, black coffee or unsweetened tea has been shown in RCTs to reduce calorie intake and improve metabolic markers within weeks.

**Read labels intelligently.** Sugar appears under more than 60 names on ingredient lists including: sucrose, glucose syrup, high-fructose corn syrup, dextrose, maltose, treacle, agave nectar, cane juice, barley malt. If sugar (in any form) appears in the first three ingredients, the product is high in added sugar.

**Retrain your palate gradually.** Reducing sugar in coffee by 25% every two weeks, diluting fruit juice with increasing amounts of water, and choosing less-sweet snack options allows taste preferences to adjust. Research shows taste preferences shift within 3–6 weeks of reduced sugar exposure.

**Use whole fruit to satisfy sweet cravings.** Berries, apples, oranges and stone fruits provide sweetness alongside fibre, water and micronutrients. A study in PLOS Medicine found that replacing SSBs with whole fruit was associated with reduced diabetes risk, while replacing SSBs with fruit juice was not.

**Cook more at home.** Restaurant and processed food is the primary source of hidden added sugar. Sauces, condiments, bread, soups and savoury snacks commonly contain substantial added sugar. Cooking from whole ingredients eliminates most hidden sources.