Types of carbohydrate
- Sugars: monosaccharides (single sugars: glucose, fructose and galactose) and disaccharides (double sugars: sucrose, lactose and maltose).
- Starch is a polysaccharide (many sugars joined): found in bread, pasta, rice and potatoes.
- Dietary fibre is a polysaccharide the body can't digest: found in wholegrains, fruit, vegetables and pulses.
Functions and needs
- Carbohydrates are the main source of energy. 1 g provides about 4 kcal (3.75 kcal).
- About 50% of our energy should come from carbohydrates, mostly starchy foods, and free sugars should be no more than 5% of energy.
- Fibre keeps the digestive system healthy, prevents constipation and helps you feel full. Adults need about 30 g a day.
- Starchy foods release energy slowly; sugary foods give a quick burst.
Too little or too much
- Excess: weight gain and obesity, tooth decay (from sugar) and a higher risk of type 2 diabetes.
- Too little: tiredness and low energy; protein may be used for energy instead of growth.
- Too little fibre: constipation and a higher risk of bowel disease.
Key terms
- Monosaccharide
- A single sugar unit, such as glucose.
- Disaccharide
- A double sugar, such as sucrose.
- Polysaccharide
- Many sugar units joined, such as starch.
- Dietary fibre
- Carbohydrate the body can't digest, which helps digestion.
- Free sugars
- Sugars added to food, plus sugars in honey, syrups and juices.
- Starch
- A complex carbohydrate found in bread, pasta, rice and potatoes.