3 mins

What is a carb?

There are three main types of carbohydrates in food. Knowing what foods these are in and how much of each to eat can be confusing. Here we explain these carb types in more detail, to help you make more informed choices when planning your meals and snacks.

01 May 2024
Fresh loaf of bread sliced on a chopping board

Why are carbohydrates important?

Carbohydrates are often the main source of energy in our diet1. When you eat and drink carbohydrates, they are broken down into glucose, increasing the level of glucose in your blood2. Therefore, the amount and types of carbohydrates that you consume can directly affect your blood glucose levels.

On nutrition labels, "total carbohydrate" includes all three types of carb so this is the number you should pay attention to when carb counting.

Complex vs simple carbs

Carbohydrates are made up of lots of sugar molecules joined together3. Simple carbs are made up of either one or two sugar molecules joined together, for example, glucose, fructose and lactose. Simple carbs are broken down quickly, and so cause a faster and shorter increase, or a ‘spike’, in blood sugar levels4.

Complex carbs, on the other hand, are made from many simple sugar molecules joined together. For example, starch is made up of three glucose molecules attached to each other3. Complex carbs are broken down more slowly, therefore they release a more steady supply of glucose over a longer period of time4.

Starch - complex carb

Foods high in starch include vegetables like peas, corn and potatoes5, dried beans, lentils, and grains like oats, barley and rice. The grain group can be broken down further into whole grains or refined grains. Whole grains are the healthier choice as the refining process removes some of the goodness contained in the outer two layers, including fibre, B vitamins and minerals, and essential fatty acids. Whole grains take longer for your body to break down and are slower releasing than refined starches.

Fibre - complex carb

Fibre comes from the indigestible part of plant foods and includes fruits, vegetables, whole grains, nuts and legumes. Fibre contributes to digestive health and helps to keep you feeling full and satisfied after eating. For good health, aim to eat between 25-30g of fibre each day. Good sources include: beans and legumes, fruit and vegetables, whole grain pasta and bread, oats, and nuts (but watch portion size as nuts are high in good fats and calories).

Sugar - simple carb

There are two main types of sugar – naturally occurring sugars found in fruit and milk and sugars added to processed foods. Sources of added sugar to look out for include: raw sugar, brown sugar, corn syrup and high fructose corn syrup, glucose, fructose, sucrose, fruit juice concentrate, honey, maple syrup, molasses. On nutrition labels "total sugars" refers to both natural and added sugar. Try to avoid some of the most common refined sources of simple carbs, like cakes and biscuits, and look for healthier alternatives like dried fruit.

How much to eat of each carb?

Foods that are higher in fibre and wholegrains, rather than refined carbs or those with added sugars, are better for our overall health1. It is recommended to get the majority of your carb intake from foods high in fibre, such as wholegrain bread, fruit, vegetables, nuts and seeds2. Try to eat less foods that contain highly processed, refined carbohydrates, such as sugary drinks, white bread, sugary cereal, cakes and biscuits2.



  1. American Diabetes Association. Understanding Carbs [Online]. Available at: https://diabetes.org/food-nutrition/understanding-carbs (Accessed 1st May 2024).
  2. Lane Community College. Types of Carbohydrates [Online]. Available at:https://media.lanecc.edu/users/powellt/FN225OER/Carbohydrates/FN225Carbohydrates2.html (Accessed 1st May 2024).
  3. American Heart Association. Carbohydrates [Online]. Available at: https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/carbohydrates (Accessed 1st May 2024).

This content is provided for general information only. It is not intended to amount to advice on which you should rely – you must obtain professional or specialist advice from your healthcare professional before taking, or refraining from, any action on the basis of the content. Although we make reasonable efforts to ensure that the content is up to date, Roche makes no representations, warranties or guarantees, whether expressed or implied, that the content is accurate, complete, up-to-date or that it should be relied upon.