Carbohydrate as a nutrient

Carbohydrate has many important functions as a nutrient:

• It provides energy. One gram of carbohydrate in the form of starch or sugars provides 3.75kcal (16kJ). For the purposes of food labelling, a conversion factor of 4kcal (17kJ) is used. It has recently been agreed by the European Commission that dietary fibre also makes a small contribution to energy as it is digested in the large bowel by the resident bacteria. An energy value of 2kcal/g (8.4kJ) has been attributed to dietary fibre.

• The body’s tissues require a constant supply of glucose, which is used as a fuel. The main source of glucose is dietary carbohydrate but it can also be synthesised from protein. If the diet is low in carbohydrate, a greater percentage of dietary protein is used to provide glucose, which means less is available for the growth and repair of body tissues. Thus, carbohydrate in the diet has a protein-sparing effect.

• Most foods contain some carbohydrate. Table 1 shows a selection of foods that contain carbohydrate, listing their sugars, starch and fibre content.

Table 1. Carbohydrate content of selected foods (per 100g)

Food (per 100g) Energy value Kcal/KJ Carbohydrate (g) Sugars (g) Starch (g) Fibre (AOAC) (g)
Brown rice, boiled 132/562 29.2 0.1 29.0 1.5
Spaghetti, white, cooked 141/601 31.5 1.0 30.5 1.7
Spaghetti, wholemeal, cooked 134/569 27.5 Tr 27.5 4.2
Baked potato (with skin)  97/413  22.6 1.4  21.2  2.6
Wholemeal bread 217/922 42.0 2.8 39.3 7.0
White bread 219/931 46.1 3.4 42.7 2.5
Lentils, red, cooked  100/424 17.5 0.8 16.2 2.5
Peas, cooked 79/329 10.0 1.2 7.6 5.6
Sweetcorn, canned 78/330 13.9 7.5 6.2 3.1
Banana 81/348 20.3 18.1 2.2 1.4
Raisins 272/1159 69.3 69.3 0 2.66

Carbohydrates in the diet

The National Diet and Nutrition survey of UK adults found the average daily intake of carbohydrate was 252g for men and 198g for women, representing 47.5% and 48.3% of food energy intake for men and women, respectively. As shown in Figure 2, cereal and cereal products were the main source of carbohydrate for adults in Britain (including 20% of carbohydrate in the form of bread).

The contribution of different foods to the average daily non-milk extrinsic sugars (NMES) intake in British adults is shown in Table 2. Intake of NMES exceeded the dietary reference value of 11% of dietary energy in all age groups and was highest in children and in elderly people in institutions. The average NMES intake in men was 12.8% of food energy, while in women NMES contributed 11.8% of food energy. Among children, NMES contributed, on average, 15.1% and 14.7% of food energy for boys and girls, respectively.

Table 2: Percentage contribution of food types to average daily non-milk extrinsic sugar intake of British adults.

Food/drink type % contribution to average daily NMES intake
Drinks 36%
Sugars, preserves and confectionery 27%
Cereal and cereal products 20%
Milk and milk products 6%
Other foods 11%