Carbohydrates are compounds that your body needs for energy. When you eat foods that contain carbohydrates, your body converts them into glucose (sugar), which your body uses for fuel.
There are different types of carbohydrate, they aren't all the same.
- Sugar. Sugars are found naturally in some foods, such as fruit, honey and vegetables. Processed sugar is added to foods such as biscuits and soft drinks during their manufacture.
- Starch. Starches are made up of a number – sometimes hundreds – of sugar molecules joined together. They are found in bread, pasta and rice, as well as some fruits and vegetables.
- Fibre is also classed as a carbohydrate. However, unlike other types of carbohydrate, your body doesn't use it for energy; it helps to keep your bowel active and healthy.
Carbohydrates are your body’s main source of energy. You use them to fuel activity in your muscles and also to keep your brain and other organs working properly.
Say the word ‘carbohydrates’ and many people will immediately think negatively. Carbohydrates have been blamed for feeling tired, bloated and a perceived heaviness. It's also a common misconception that carbohydrates are fattening. 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.
It's not unusual to think of cakes and stodgy food when carbohydrates are mentioned but remember carbohydrates aren't all the same. Low-carb diets often don’t leave room for fruit, vegetables and whole grains, which contain carbohydrates and are essential components of a balanced diet. It's the sugar type of carbohydrate, found in biscuits and fizzy drinks and the like that gives you a sugar rush and is the main problem. Your body processes such sugars very quickly so they don't sustain your energy levels. And we know we should all be eating less of them. See ‘What is the glycaemic index?’ for more information on how quickly carbohydrates are broken down.
Carbohydrates do contain calories but fewer than half the number that are in fat. Of course, as with lots of things, it’s not good to have too much carbohydrate. If you eat more carbohydrate than your body can burn off as energy, the excess will be converted to fat. But carbohydrates are an essential part of a healthy diet.
Rather than eliminate carbohydrates from your diet, the key thing is to eat the right type of carbohydrate because some are healthier than others.
'Good' carbohydrates are the wholegrain varieties of starchy carbohydrates. High-fibre, starchy carbs release sugar into your blood more slowly than sugary foods and drinks. This makes them an important source of energy. See ‘What is the glycaemic index?’ below for information on how quickly different carbohydrates release sugar.
Wholegrains contain a host of important nutrients that may reduce your risk of heart disease and some types of cancer. When grains are processed to make them look whiter, the part of the grain that contains fibre and many useful nutrients is removed. This means that white bread, pasta and cereals aren’t as good for you as the wholegrain varieties.
Wholegrains are also more likely to keep you feeling fuller for longer. This is because they contain more fibre and generally take longer to digest than foods that have been processed.. This can help to control your appetite and help you to maintain a healthy weight.
Sugar is often referred to as a 'bad' carbohydrate. Sugary foods and drinks contribute to your energy intake but have little other value. Not only that, they are often very energy dense, which means they pack a lot of calories into a small volume. Some of these foods also contain a lot of fat but not many other useful nutrients. The calories they contain are often called ‘empty calories’ because of the lack of nutrients. Even if you eat just a small amount of sugary foods and drinks, they can push up your calorie intake remarkably quickly. In fact, sugary drinks are the main reason many of us consume too many empty calories.
It’s best to limit your intake of 'bad' sugar carbohydrates and stick to 'good' starchy foods. But remember to include some fruit in your diet because it has other important nutrients, such as vitamins.
At least half the energy in your diet should come from carbohydrates, ideally wholegrain starchy carbohydrates. So include things like wholemeal bread, brown pasta and rice, as well as some fruits and vegetables. Most of us are already eating enough carbohydrate, but often of the wrong type. Too many calories come from sugary products and not enough from wholegrain, starchy foods.
If you don't eat enough carbohydrate, you may have low blood-sugar levels; this is called hypoglycaemia. This condition will make you feel weak and light-headed. Because your brain needs fuel from carbohydrates, you might also have difficulty concentrating. However, hypoglycaemia mainly affects people who have diabetes, as well as very active sports people.
Aim to make starchy foods about a third of your diet. The easiest way to do this it to try to include wholegrain starchy foods in every meal.
Instead of... Go for... white bread wholemeal or granary bread, pitta, or tortilla wraps white pasta and rice
brown pasta and rice
leave the skin on boiled potatoes or cook wedges with the skin on
sweet potatoes and yams, or substitute beans or chickpeas meat-centric meals
beans and lentils in stews, casseroles and curries; you won’t need to use as much meat, so your meal will be lower in saturated fat too (gram for gram, carbohydrate contains less than half the calories of fat)
sweets, cakes and biscuits
a piece of fruit, dried raisins or vegetable sticks
unsweetened wholegrain cereals (check the label) such as porridge
fries or chips
quinoa, couscous, wholemeal pasta, rice or noodles
fruit juice or smoothies – but only one a day as they also have lots of sugar; keep yourself hydrated with less-sugary drinks or water the rest of the time
popcorn – great news, it's a wholegrain (but choose plain over salted and sweetened varieties)
The glycaemic index (GI) is a rating system for foods that contain carbohydrates. It shows how quickly each food affects the sugar levels in your blood. Low-GI foods cause blood sugar levels to rise and fall slowly, so you feel fuller for longer.
Low GI foods include wholegrain foods, some fruits and vegetables, beans and lentils.
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, carrots have a high GI, while chocolate and ice cream have a lower GI. Obviously, carrots are much the healthier option! Bear this in mind if you're relying on the GI value to decide if foods are healthy or will help you to lose weight. Consider the bigger picture!
Some people aren't able to digest certain carbohydrates. This is called carbohydrate intolerance. The carbohydrate most commonly involved is lactose (the sugar found in milk and dairy products) and the inability to digest lactose is called lactose intolerance.
Carbohydrate intolerance causes symptoms such as diarrhoea, bloating, and wind when you eat the carbohydrate you can’t digest. If you notice any of these symptoms, contact a dietitian. It's a good idea to keep a food diary before your appointment so you can pinpoint what causes your symptoms.
Treatment for the condition is to remove from your diet the type of carbohydrate that causes you problems. Your dietitian will help you figure out how to do this and which foods to avoid, and how to top up with alternative carbohydrates.
- Draft carbohydrates and health report. Scientific Advisory Committee on Nutrition. www.gov.uk, published 2014
- Carbohydrates. British Dietetic Association. www.bda.uk.com, reviewed April 2013
- What to eat on the paleo diet. The Paleo Diet. www.thepaleodiet.com, accessed 27 May 2015
- Overview of nutrition. The Merck Manuals. www.merckmanuals.com, published November 2013
- What is a healthy balanced diet? Food Standards Agency. www.food.gov.uk, published 20 August 2014
- Healthy weight loss. British Nutrition Foundation. www.nutrition.org.uk, reviewed 21 December 2012
- Maintaining a healthy weight and preventing excess weight gain among adults and children. National Institute for Health and Care Excellence (NICE), 13 March 2015. www.nice.org.uk
- Empty calories. United States Department of Agriculture. www.choosemyplate.gov, accessed 1 June 2015
- Healthy diet. World Health Organization. www.who.int, published May 2015
- Healthy diet and enjoyable eating. PatientPlus. www.patient.co.uk/patientplus.asp, reviewed 18 February 2011
- Glycaemic index (GI). British Dietetic Association. www.bda.uk.com, reviewed December 2013
- Behaviour change and obesity. British Nutrition Foundation. www.nutrition.org.uk, reviewed 26 June 2012
- Bread, rice, potatoes, pasta and other starchy foods. British Nutrition Foundation. www.nutrition.org.uk, reviewed May 2014
- Healthy packed lunches. British Nutrition Foundation. www.nutrition.org.uk, reviewed June 2014
- Lactose intolerance. PatientPlus. www.patient.co.uk/patientplus.asp, reviewed 10 December 2013
- Carbohydrate intolerance. The Merck Manuals. www.merckmanuals.com, published 1 June 2015
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