Meal preparation

The facts on carbohydrates

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Carbohydrates sometimes get a bad rap, but not only do they provide a valuable source of energy, they’re actually your body’s preferred fuel source. Learn why this is, how many to eat and why some carbohydrates are healthier than others.

Confused about whether carbohydrates are healthy or not? You’re not the only one. As a result of low-carb weight-loss diets making headlines, there are more than a few misconceptions doing the rounds about carbohydrates.

The first thing to know is that you don’t need to eliminate carbohydrates to lose weight. In fact, eating wholegrains plays a key role in controlling weight and in reducing the risk of weight gain.

Here are a few other important things to know about carbohydrates.

What are carbohydrates, anyway?

Sugars, starches and some types of dietary fibre are carbohydrates. The digestive system breaks them down into simple sugars – mainly glucose – which are carried to your body’s cells via the bloodstream. Once they’re inside a cell, these simple sugars are burned to produce energy.

The body converts any leftover glucose into glycogen and stores it away in the liver and muscles, to use when it needs a quick boost of energy or if blood glucose levels run low.

Why does your body need them?

Carbohydrates are essential for good health and a well-balanced diet. As well as being the body’s preferred energy source because they provide a quicker and more efficient energy supply than protein or fat, they’re the only fuel source for a range of vital organs, including the brain.

Plus, a lot of carbohydrate-rich foods deliver other health benefits, too. Many are high in dietary fibre, which helps keep the digestive system healthy and can even act as a prebiotic, encouraging the growth and activity of ‘good’ gut bacteria.

Which foods provide carbohydrates?

You’ll find carbohydrates in grain-based foods like bread, breakfast cereal, rice, pasta, quinoa and cous cous, as well as fruit, legumes, milk, yoghurt, corn, potato and other starchy vegetables. Sugar, honey, biscuits, cakes and lollies also contain carbohydrate.

After reading that list, you’re probably thinking that not all carbohydrates are created equal – and you’re right.

On top of the fact that some carbohydrate-rich foods contain vitamins, minerals and other important nutrients while others don’t, some are also digested more slowly than others to provide longer-lasting energy.

What is the glycaemic index?

The glycaemic index (GI) was developed to rank carbohydrates based on how they affect blood glucose levels.

Carbohydrates that break down rapidly during digestion and release their glucose into the bloodstream quickly - like baked potatoes - have a GI of more than 70. Those that break down slowly, so that they release glucose more gradually into the bloodstream - like oats - have a GI less than 55. In many cases, when you choose a wholegrain or higher fibre option, it also means you’re choosing the lower GI option.

However, while the GI is useful as a guide when you’re selecting which carbohydrates to eat, particularly when you’re comparing ‘like for like’ foods such as having oats instead of cornflakes or choosing grainy instead of white bread, there are some limitations to bear in mind. Like the fact that some healthy foods, including certain fruits, vegetables and cereals, have a higher GI than biscuits and cakes.

This doesn’t mean the latter is better for you! It’s always important to consider the whole food, taking into account the other nutrients they do, or don’t, deliver.

How many carbohydrates should you eat?

According to official guidelines, 45-65 per cent of your daily energy should come from carbohydrates. For someone eating an average amount of daily kilojoules, that means eating between 230 and 330 grams of carbohydrates a day, remembering that:
  • Two slices of wholemeal bread = 24g of carbohydrates
  • Half-a-cup of brown rice = 25g of carbohydrates
  • A medium banana = 22g of carbohydrates
  • A cup of lentils = 19g of carbohydrates
  • A 200g tub of natural yoghurt = 10g of carbohydrates

One way to ensure you’re eating enough carbohydrates, as well as meeting your other nutritional needs, is by sticking to the New Zealand Dietary Guidelines, which suggest that you daily should:

  • Enjoy a variety of nutritious foods every day including plenty of vegetables and fruit
  • Enjoy a variety of nutritious foods every day including grain foods, mostly whole grain and those naturally high in fibre