Doug Ross

Good VS Bad Carbohydrates: Everything You Need To Know

Analysing the differences between nutritious and unhealthy carbohydrates.

good and bad carbs

As one of the three macronutrients alongside fat and protein, carbohydrates play a fundamental role in our diets. However, while some carbohydrates offer several health benefits, others can contribute to various medical conditions. In this article, we’ll dive into the world of carbohydrates, explore the differences between the good and the bad, and how to find the right dietary balance.

What are carbohydrates?

Carbohydrates, a mainstay macronutrient found in pasta, bread, and rice, and exist in various forms, including sugar, starch, and fibre. But how do these differ?

Sugar is the simplest form of carbohydrate, providing quick energy when rapidly absorbed into the bloodstream. Sugars can be found naturally in fruits, vegetables, and dairy products.

Starch on the other hand is a complex carbohydrate, consisting of long chains of glucose molecules. It serves as the main carbohydrate storage in plants providing vital energy. Starchy foods like potatoes, corn, legumes, and rice take longer to digest and offer a more sustained energy release to sugar.

Fibre is also a complex carbohydrate but our bodies can’t fully digest it. You can primarily find fibre in plant-based foods such as fruits, vegetables, whole grains, nuts, and seeds. Furthermore, there are two types, soluble and insoluble.

Soluble fibre dissolves in water and can be metabolised by the ‘good’ bacteria in the gut. It soaks up water like a sponge and helps to bulk out stool, meaning it can pass through the gut more easily. Insoluble fibre does not dissolve in water and passes through the digestive system relatively intact. It does not absorb water and speeds up the time that food passes through the gut.

So, what makes any of these carbohydrates good?

Complex – good – carbohydrates


Foods that contain good carbohydrates – often referred to as complex carbohydrates – are minimally processed, and typically rich in fibre, vitamins, and minerals. Some examples of good carbohydrates include whole grains like oats, brown rice, and quinoa, as well as fruits and vegetables. Let’s take a look at some of the positive effects they have on our health.

1Provide energy and a prolonged feeling of fullness

The more gradual and sustained release of glucose into the bloodstream helps regulate blood sugar levels and promotes feelings of fullness and satiety. Furthermore, fibre found in good carbohydrates can increase the feeling of fullness by soaking up water in the intestine and slowing the absorption of nutrients. Subsequently, the urge to consume more food may become reduced.

2Promote digestive and gut health

One of the main benefits of increasing fibre intake is reduced constipation, through adding bulk to stool. Some dietary fibres also feed the ‘good’ gut bacteria in the intestines. These bacteria produce nutrients such as short-chain fatty acids, which can improve digestive disorders and immune function, and reduce gut inflammation.

3Improve insulin sensitivity

Complex carbohydrates allow the body to use insulin more effectively to maintain healthy blood sugar levels. Not only is this important for individuals with diabetes, but also for those who are at risk of developing the disease. A systematic review of 22 randomised controlled trials containing 911 participants illustrates that soluble fibre products and fibre from natural foods are effective in improving glycemic control and insulin sensitivity.

4Support weight management

Fibre can increase the feeling of fullness by soaking up water in the intestine and slowing the absorption of nutrients. This means you are likely to eat less, cutting your overall daily calorie consumption. In addition, the more gradual and sustained release of glucose into the bloodstream helps regulate blood sugar levels and promotes feelings of fullness and satiety. Increasing fibre intake by 14g per day can decrease energy intake by 10%, resulting in body weight loss of up to 2kg over 4 months.

5Normalise blood cholesterol levels

Fibre-rich diets have the ability to decrease the risk of heart disease by reducing blood cholesterol levels. In fact, increasing fibre intake by 7g per day, can result in a 9% decrease in likelihood of heart disease.

Simple – bad – carbohydrates


Bad carbohydrates, otherwise known as simple carbohydrates, are highly processed and stripped of their natural fibre and nutrients. They are digested quickly and have a high glycemic index (GI), which leads to a rapid spike in blood sugar levels. Examples include sugar-sweetened beverages (SSBs), snacks and white bread. Let’s take a look at some of the negative effects they have on our health.

Contribute to diabetes and obesity development

Repeated spikes in blood sugar can cause the body to become less sensitive to insulin, leading to a condition called insulin resistance, a significant risk factor for type 2 diabetes, heart disease and obesity.

Increase the risk of cancer

Consuming high GI carbohydrates causes a rapid increase in blood sugar levels, leading to elevated insulin production. Although insulin is a hormone that regulates blood sugar, it also stimulates cell growth and division. Unfortunately, higher levels of insulin in the body, can promote the growth of cancer cells and potentially increase the risk of developing cancer.

Increase the risk of heart disease

Processed carbohydrates with added sugars, can cause chronic inflammation in the body. Furthermore, inflammation increases the risk of heart disease, as it often results in damaging the lining of blood vessels, leading to atherosclerosis and the formation of plaque. These inflammatory processes also contribute to the rupture of plaque, triggering blood clots and increasing the likelihood of heart attacks and strokes. Over the course of a 15-year study participants who took in 25% or more of their daily calories as sugar were more than twice as likely to die from heart disease as those whose diets included less than 10% added sugar.

Contribute to oral health problems

The sugars found in SSBs interact with the bacteria within plaque and produce acid. This slowly dissolves enamel creating holes or cavities in the teeth, leading to tooth decay and tooth abscesses, even when SSB intake is less than one time per day.

Impact mood negatively

Consuming high-GI foods results in a sudden burst of energy. However, this doesn’t last long and leads to a dramatic drop in energy, causing fatigue. What’s more, spikes in blood sugar also cause an imbalance in hormone levels, particularly the stress hormone cortisol. This can lead to feelings of anxiety and irritability.

What carbs should you eat and how? Eight simple tips

Now we know the importance surrounding the type of carbohydrates we consume, here’s that knowledge rounded into eight simple tips.

1Snack on high-fibre foods

Instead of grabbing the nearest bag of crisps or cookies, choose snacks like fresh fruit. Fruits are an excellent source of fibre and contain other essential nutrients.

2Keep an eye out for nutrient-rich carbohydrates

Choose carbohydrates that are rich in nutrients such as whole grains, fruit and vegetables. These foods are typically lower in calories and higher in fibre, vitamins, and minerals, which help to support and maintain several bodily functions.

3Consume a wide range of fruit and vegetables

The vast majority of fruits and vegetables have a low GI, making them an excellent choice for maintaining blood sugar levels.

4Find the right balance of carbohydrates

Although carbohydrates are an important part of a healthy diet, it’s advised to balance them with other macronutrients, like protein and fat. The Scientific Advisory Committee on Nutrition (SACN) recommends that the dietary reference value (DRV) for carbohydrates should be at a population average of approximately 50% of our daily intake, and that the DRV for fibre for adults should be 30g/day.

5Avoid foods with high added sugar content

Processed foods, such as SSBs, sweets, and baked goods, can be extremely high in added sugars.

6Hydrate regularly


Fibre won’t prevent constipation unless the individual drinks enough water every day.

7Switch to healthier cooking methods

The processing and cooking of foods can affect GI levels. For example, roasting or baking may result in higher GI. On the other hand, boiling and steaming foods may contribute to a lower GI diet.

8Increase the amount of fibre in your diet gradually

Stick to the recommended intake and slowly introduce fibre into a diet. A sudden switch from a low-fibre diet to a high-fibre diet can lead to abdominal pain and increased wind.

Curious facts about carbohydrates

  • Ancient civilisations used materials like wood, straw, and dried dung, which are rich in carbohydrates, to create fire and generate heat.

  • The Maillard reaction is a chemical reaction that occurs between carbohydrates and amino acids when heated. It’s responsible for the browning and delicious flavours in foods.

  • Some marine animals such as sea cucumbers produce a unique carbohydrate called trehalose, which helps them survive in extreme environments, such as freezing temperatures and droughts.

Let’s summarise

Understanding the difference between good and bad carbohydrates is vital for maintaining a healthy diet. Good carbohydrates provide essential nutrients, and dietary fibre, while bad carbohydrates can contribute to weight gain and an increased risk of disease. By making conscious choices and prioritising the right carbohydrates an improvement in overall well-being is likely to follow.

Want to know some more about carbohydrates?

In this video, Dr. Jason Fung discusses the role of carbohydrate restriction in weight loss and emphasises that not all carbs are equal when it comes to their impact on weight.

Healthypedia FAQ

The RDI varies depending on factors ranging from age, sex, weight, and exercise. As a general guideline, carbohydrates should make up 45-65% of the daily calorie intake.

Cooking process can in fact break down some of the fibre in vegetables, however in other cases, cooking can actually make fibre more digestible and increase its availability. Therefore it’s recommended to consume a mix of raw and cooked vegetables.

Low-carbohydrate diets can be healthy but they need to be done properly and under the advice of a healthcare professional. It's essential to still consume enough nutrients and fibre to support overall health and well-being.

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