McCance and Widdowson shows 100g sugar containing 105g sugar – why?

Carbohydrate values in McCance and Widdowson (M&W) series of publications are expressed as monosaccharide equivalents.

These values can exceed 100g per 100g of food because on hydrolysis 100g of a disaccharide, such as sucrose, gives 105g monosaccharide (glucose + fructose).


Thus white sugar appears to contain 105g carbohydrate (expressed as monosaccharide) per 100g sugar.
For conversion between carbohydrate weights and monosaccharide equivalents, the values shown in Table 1 below (adapted from M&W introduction) should be used.

In trying to explain this to students (depending on the age) you could explain this using chemistry and molecular weights:

Sucrose + water → glucose + fructose

C12H22O11 + H2O → C6H12O6 + C6H12O6

342g + 18g → 180g +180g

So in this example you can see 342g of the disaccharide sucrose gives 360g monosaccharides.

Table 1



Conversion of carbohydrate weights to monosaccharide equivalents


Carbohydrate Equivalents after



Conversion to




Monosaccharides e.g. glucose,

fructose and galactose





no conversion



Disaccharides e.g. sucrose,

lactose and maltose






x  1.05


Oligosaccharides e.g.

raffinose (trisaccharide)

stachyose (tetrasaccharide)

verbascose (pentasaccharide)








x  1.07

x  1.08

x  1.09


Polysaccharides e.g. starch






x  1.10

Cut down on your sugar!

Manufacturers have been asked to reduce sugar content of food to 5% of daily energy.

The previous guidance was 10% of daily energy, but 5% is in line with the World Health Organisation.
The report from the Scientific Advisory Committee  SACN is available online.

The recommended limits are

25g (5-6 teaspoons) of sugar for women

35 g (7-8 teaspoons) for men.


The report said sugary drinks such as fizzy drinks and squash should be reduced for children and adults.

Food Manufacture Magazine has an interesting audio presentation for this article.

’30% of teenager’s calories are coming from soft drinks’ says Dr Alison Tedstone, Public Health England’s chief nutritionist.

How can manufacturers reformulate products to contain less sugar?

Swap sugar for low sugar alternatives. Also reduce sugar content of drinks – people are adapted to sweet taste. Can do the same as salt reduction.

Consumption of sugary drinks increases childhood obesity. This includes fruit juice – contains the same amount as fizzy drink.

Public Health England is launching campaign to encourage sugar reduction.

Thinking about taxing sugary drinks, restricting advertising, and digital media.

The Nutrition Program can be used to show you the % of sugar in your products based on current RI recommended intakes.

Current recommendations for energy intakes are for 50% to come from carbohydrates in the form of starchy foods and whole grains.

Dr Ann Prentice, chair of SACN, said ‘There is strong evidence to show that if people have less free sugars and more fibre in their diet, they can lower the risk of cardiovascular disease, type 2 diabetes and bowel cancer.’