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Carbohydrates


Expert reviewer Mr Paul McArdle, Registered Dietitian
Next review due April 2023

Carbohydrates are an important part of a healthy diet. They provide us with energy, as well as essential nutrients that our body needs to function properly. However, not all types of carbohydrate are good for us. What’s important is to eat the right type and amount of carbohydrate.

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Why do we need carbohydrates?

Carbohydrates are an important source of energy for your body. Although fats and protein provide energy, carbohydrates are the preferred type of energy source for your brain and nervous system. Your body also uses them to fuel activity in your muscles and keep other organs working properly.

Even when your body breaks down fat for energy, you still need a certain amount of carbohydrate for this process to happen properly. Wholegrain, starchy carbohydrates are also an important source of other essential nutrients, including fibre.

Types of carbohydrate

Not all carbohydrates are the same. There are different types of carbohydrate.

  • Sugar. Sugar may be found naturally in foods such as whole fruit and vegetables, milk and dairy products. It’s also added to some foods during manufacture – for example, sweets, biscuits and fizzy drinks. These added sugars, also known as free sugars, can be harmful to your health and should be eaten only in moderation.
  • Starchy or ‘complex’ carbohydrates are made up of a number – sometimes hundreds – of sugar molecules joined together. They’re found in bread, pasta and rice, as well as some fruits and vegetables. Starchy foods can be whole (for example, wholegrains) or refined or processed (for example, white bread).

Carbohydrates are broken down in our bodies into simple units of glucose. These are used as a source of energy in the body. Different carbohydrate-containing foods are broken down at different rates, some faster and some slower. See our section on the glycaemic index for more information.

What are good and bad carbohydrates?

Good carbs

Generally, carbohydrates in their natural form – that is, they haven’t been processed – can be thought of as ‘good carbs’ because they tend to be healthier. These include:

  • the natural sugars found in whole fruit and vegetables and in milk and dairy products
  • the wholegrain, high-fibre varieties of starchy carbohydrates.

As well as natural sugars, fruit and vegetables contain a range of essential nutrients, such as vitamins, minerals and fibre. Dairy products are an important source of calcium. Wholegrains also contain a host of important nutrients that may reduce your risk of heart disease and some types of cancer. These are removed when grains are processed.

Sources of wholegrain and high-fibre carbs include wholegrain bread, brown rice, whole-wheat cereals, and potatoes with the skin left on. These carbs provide a steady source of energy because they release sugar into your blood more slowly than sugary foods and drinks or refined carbs like white bread. This can keep you feeling fuller for longer, helping to control your appetite and maintain a healthy weight. For information on how quickly different carbohydrates release sugar, see our section on the glycaemic index.

Bad carbs

The ‘free’ sugars added to processed foods and drinks – like biscuits, fizzy drinks, chocolate and cake – can be thought of as ‘bad carbs’. These foods and drinks contribute to your energy intake by packing a lot of calories into a small volume, but often don’t have other useful nutrients. In fact, sugary drinks are one of the main contributors to overall sugar intake for many of us. Sugary foods and drinks also lead to tooth decay.

Free sugars are also naturally present in honey, syrups and fruit juices so it can be confusing to understand what’s good and bad. What’s important is to be aware of these free sugars and try to reduce your sugar intake when you can.

Processed or refined starchy carbohydrates, as in white bread, pasta and cereals, are less healthy than wholegrain varieties. This is because when grains are processed to make them look whiter, the part of the grain that contains fibre and many useful nutrients is removed.

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How much carbohydrate do I need?

AAim to make starchy foods – ideally wholegrain starchy carbohydrates – about a third of your diet. Include things like wholemeal bread, brown pasta or brown rice in every meal, as well as some fruits and vegetables. See the Eatwell Guide below to compare other food groups.

An image showing the recommended balance of the five major food groups


In general, a portion of carbohydrate for one meal should be about the size of your fist. The exact amount you need differs from person to person. It depends on many things, including your gender, age and activity levels.

In the UK, Public Health England publishes Dietary Reference Values (DRVs) for all types of nutrient, for men and women in different age groups. Reference intake (RI) values are given for carbohydrates, as a guide for how much you should be aiming to eat per day. Food labels will tell you how much carbohydrate a product contains, and the percentage of the RI this equates to. It’s important to bear in mind that the values given on food labels are for an average adult woman – the amount you need may be very different.

Most of us are already eating enough carbohydrate, but often of the wrong type. We tend to have too much sugar and not enough wholegrain, starchy foods. We should be aiming to switch to healthier carbs where we can.

Eat the right carbohydrates – food swaps

Instead of... white bread
Go for... wholemeal, wholegrain or granary bread, pitta, or tortilla wraps

Instead of... white pasta and rice
Go for... whole-wheat pasta and brown rice

Instead of... peeling potatoes
Go for... leaving the skin on boiled potatoes or cooking wedges with the skin on or swapping white potatoes for sweet potatoes and yams

Instead of... fries or chips
Go for... quinoa, couscous, bulgur wheat, barley, wholemeal pasta, rice or noodles

Instead of... crisps
Go for... popcorn – but choose plain over salted and sweetened varieties

Instead of... sweets, cakes and biscuits
Go for... a piece of fruit, wholegrain cereal bars, oat cakes, rice cakes or wholemeal scones

Instead of... sugary cereals
Go for... unsweetened wholegrain or wholemeal cereals such as porridge, Weetabix, Shredded Wheat and wholegrain muesli

Instead of... fizzy drinks
Go for... fruit juice diluted with sparkling water – don’t have more than one serving of fruit juice or smoothies a day because they have lots of sugar

What is the glycaemic index?

TThe glycaemic index (GI) is a measure of how quickly carbohydrate in your food is digested and broken down into sugar molecules. Foods are given a rating from 1 to 100, depending on how quickly they affect the sugar level in your bloodstream.

Low-GI foods cause blood sugar level to rise and fall slowly, so you feel fuller for longer. These include many wholegrain foods, some fruits and vegetables, and beans and lentils. Foods with a high-GI are broken down quickly, causing a sharp rise in your blood sugar.

Although it’s a good idea to include low-GI foods in your diet, don’t use this measure alone to decide if a food is healthy. For example, watermelon is healthy, but has a high GI, while the GI for chocolate and ice cream is relatively low, due to their fat content. Bear this in mind if you’re relying on the GI value to decide if foods are healthy or will help you to maintain weight.

Click to open a PDF version of Bupa's Glycaemic index (0.6MB)

GI-infographic-470px

Cutting out carbs

There’s a common misconception that carbohydrates are fattening. So, if you’re looking to lose weight, you might wonder if cutting out carbs or going for a low-carbohydrate diet is a good approach to take.

Some diet plans, such as the paleo diet (also known as the caveman diet) and the Atkins diet are based on reducing the amount of carbohydrate you eat. However, there’s no evidence that diets like this are any more effective than diets that focus on reducing your fat intake. In addition, diets like this can be difficult to stick to, which won't help you to keep the weight off long-term. Low-carbohydrate diets often don’t leave room for the healthy carbohydrates in fruit, vegetables and wholegrains, which contain essential nutrients.

Carbohydrates do contain calories but less than half the number found in fat. Of course, as with lots of things, it’s not good to have too much. If you eat more carbohydrate than your body can burn off as energy, the excess will be converted to fat. But carbohydrates are an important part of a healthy diet. Rather than eliminate carbohydrates from your diet, the key thing is to eat the right type.

Lactose and other carbohydrate intolerances

Some people have a bad reaction to certain carbohydrates, including lactose and wheat, or to starchy foods that contain the protein gluten. You may have symptoms such as diarrhoea, wind, stomach pains and constipation when you eat foods that contain these substances. You’ll need to see a doctor or dietitian to rule out food allergies and medical conditions like coeliac disease.

An intolerance is when your body reacts against a certain type of food, but it doesn’t involve your immune system, so isn’t an allergy. It’s often due to a problem with your ability to digest the food. Examples include lactose intolerance and gluten intolerance. Lactose is the sugar found in milk and dairy products. Gluten is a protein found in certain grains that are used to make bread, pasta and cereals.

If your doctor or dietitian thinks you have an intolerance, they may advise you to stop eating the type of carbohydrate that causes you problems. They will talk you through how to do this, including which foods to avoid, and how to top-up with alternative carbohydrates.


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Related information

Tools and calculators

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  • Reviewed by Pippa Coulter, Freelance Health Editor, April 2020
    Expert reviewer Mr Paul McArdle, Registered Dietitian
    Next review due April 2023



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