Carbohydrates

Carbohydrates include simple sugars (mono and disaccharides; oligosaccharides) and complex carbohydrates called polysaccharides. The majority of dietary carbohydrates come from plant foods.

Examples of sources of sugars include:

• Fructose - found in many fruits and in honey.
• Glucose - small amounts are found in some plants.
• Sucrose (commonly known as table sugar) is derived from the plants sugar cane and sugar beet. It is also found in sweet root vegetables such as beetroot and carrots.
• Maltose - formed from starch in brewing.
• Lactose - found in milk and milk products and is synthesised in the mammary gland.

Digestion and metabolism

During digestion complex carbohydrates (polysaccharides) are broken down into simple sugars (monosaccharides).

• Starch and maltose to glucose
• Lactose to glucose and galactose
• Sucrose and galactose to glucose and fructose

Once absorbed, galactose is converted to glucose and or used in the synthesis of other substances. Glucose is used to produce energy or replenish glycogen stores (carbohydrate, stored in the muscles and some in the liver)

There are other carbohydrates in plant foods which we do not digest and these are major constituents of what we call dietary fibre.