How does ‘Total Carbohydrate’ differ from ‘Available Carbohydrate’?
Here at NutriCalc, we’re often asked the question ‘Are available carbohydrates and Total Carbohydrates the same?’ Sadly, the answer to this is, ‘It depends where the information comes from!’
Carbohydrates are chemical compounds that are important in nutrition. They contain carbon, hydrogen, and oxygen. And the proportions of hydrogen to oxygen are 2:1, which is what you have in water (H2O). Hence the name carbohydrate. For example, glucose is C6H12O6, so it has the equivalent of six H2O molecules.
Normal carbohydrates such as sugars and starches have this type of formula. If they can be digested by the body, they are often called available carbohydrates.
But some carbohydrates such as non-starch polysaccharides can’t be digested, and they are also described as fibre. (However, fibre usually contains other substances as well).
This means that you can add together the available carbohydrate and fibre and get a figure for total carbohydrate.
The UK and countries in the European Union declare available carbohydrate on food labels, but some countries, such as the USA, Canada, South Africa, and the Gulf States include dietary fibre and therefore declare total carbohydrate, because of the inclusion of the fibre. This can sometimes cause some mistakes when looking at an ingredient specification sheet with a view to doing a nutrition calculation. If the ingredient is from the USA etc, it’s important to deduct the fibre from the total carbohydrate to achieve a figure for available carbohydrate.
Just to make it more complicated, whilst Australia uses the term ‘total carbohydrate,’ this is actually available carbohydrate so for specification sheets supplied from here, there’s no need to make an adjustment when entering values into NutriCalc.
The way that laboratories achieve values for available carbohydrate in a food is by analysing everything else (fat, protein, moisture, fibre, and ash (inorganic matter such as salt and phosphates)) and then subtracting them all from 100%. This is declared as ‘carbohydrate by difference’ which also includes polyols (complex alcohols) and oligosaccharides (longer sugars).
Unfortunately, as this method includes the tolerances from the other nutrients, the results for carbohydrates from laboratories are often not very accurate.
Interestingly, the South Africans have a different term for available carbohydrate that is just starch and sugars, which they call ‘glycaemic carbohydrate.’
Until we achieve consistency of terms used across the Globe, understanding the current terms and how to handle them is the only option we have!