Sweeteners are substances that make foods and drinks taste sweet, but they can differ greatly in calories, chemistry, and how the body processes them. Table sugar, or sucrose, provides energy because it is digested into glucose and fructose. Sugar substitutes can provide sweetness with fewer calories because they are used in tiny amounts, are not fully absorbed, or are metabolized differently.
Understanding these differences helps students read food labels and make informed nutrition choices.
Key Facts
- Sucrose is a disaccharide made of glucose and fructose: C12H22O11.
- Carbohydrates provide about 4 kcal/g, so 10 g of sugar provides about 40 kcal.
- Relative sweetness compares a sweetener to sucrose, where sucrose = 1.
- High-intensity sweeteners such as sucralose and stevia are much sweeter than sugar, so only small amounts are needed.
- Sugar alcohols often provide fewer calories than sugar, commonly about 2 kcal/g, but values vary by type.
- Acceptable daily intake estimates a safe daily amount: ADI = mg sweetener per kg body mass per day.
Vocabulary
- Sucrose
- Sucrose is common table sugar, a carbohydrate made from one glucose unit and one fructose unit.
- Non-nutritive sweetener
- A non-nutritive sweetener provides little or no energy while producing a sweet taste.
- Sugar alcohol
- A sugar alcohol is a reduced-calorie sweetener such as xylitol or erythritol that is chemically related to sugars but absorbed differently.
- Relative sweetness
- Relative sweetness is a comparison of how sweet a substance tastes compared with the same amount of sucrose.
- Acceptable daily intake
- Acceptable daily intake is the estimated amount of a substance that can be consumed daily over a lifetime without expected harm.
Common Mistakes to Avoid
- Assuming sugar-free means calorie-free. Some sugar-free foods contain fats, starches, protein, or sugar alcohols that still provide calories.
- Comparing sweeteners only by grams used. High-intensity sweeteners may weigh far less than sugar because they are hundreds of times sweeter.
- Thinking all sugar substitutes act the same in recipes. Some provide bulk, browning, and texture, while others only provide sweetness.
- Ignoring serving size on labels. A product may look low in sugar or calories per serving, but eating multiple servings changes the total intake.
Practice Questions
- 1 A drink contains 24 g of sucrose. If carbohydrates provide 4 kcal/g, how many calories come from the sugar?
- 2 A student has a body mass of 60 kg. If a sweetener has an acceptable daily intake of 5 mg/kg/day, what is the student's daily ADI in milligrams?
- 3 A cookie recipe uses sugar for sweetness, browning, and texture. Explain why replacing all the sugar with a high-intensity sweetener might change the final cookie even if it tastes sweet.