The Truth About Carbohydrates

Carbohydrates, often referred to as carbs, are currently top of the list of nutrients we love to hate.

“No carbs before Marbs”, “I’m cutting carbs to lose weight”, “toxic”, “addictive”, “Carbs make you fat” are all things we hear too often.

They have been blamed for all sorts of public health problems such as the rise in diabetes and heart disease (1). This has led to popular diets such as the Keto diet, low carb diets and the Atkins diet gaining more traction. All the while, our social media feeds are filled with images of glorified burgers, pizzas, doughnuts, filled sandwiches… the list goes on. Yet we worry about having toast for breakfast.

As a result there is so much confusion out there about carbohydrates, should we eat them, should we not? When should we eat them? Which should we eat?

Let’s clear things up a little and look at why we should stop demonising carbs.  

To begin, let’s look at what carbohydrates actually are.  Carbohydrates are compounds of carbon, oxygen and hydrogen which can be classified in different ways. Carbs are key components of the diet and can be categorised into sugars, starchy carbohydrates and dietary fibre, each of which provide an important source of energy for the body.

Sugars are found in foods such as sweets, doughnuts, fizzy drinks and chocolate. Starchy carbohydrates are foods including potatoes, bread, quinoa, oats, rice and pasta. Fibre is also found in wholegrain breads, oats, pasta and rice as well as pulses, fruits and vegetables.  

It is recommended that at least 50% of the energy in our diets should come from carbohydrate, aiming for around one third is ideal, mostly coming from starchy sources.

So if carbs should make up this much of our diet, why are they demonised?

Let’s look at the facts…


Carbohydrates are an essential source of fuel for the brain and body. They’re broken down into glucose before being absorbed into the blood. Glucose then enters the body’s cells with the help of insulin and the glucose is used by the body for energy; fuelling everything we do from walking upstairs, breathing and talking.

The body’s tissues require a constant supply of glucose, which is used as fuel for the body.

Carbs make you happy

Our brains use glucose from carbohydrates as fuel too. So for your brain to function effectively, carbs are pretty important. They also play an important role in transporting tryptophan to the brain. tryptophan is key for creating serotonin which is a happy hormone.

Not all carbs are equal

It’s important to note that the quality of carbohydrates has a role in this conversation. Ideally, we don’t want to be getting our carbohydrate intake solely from sugar sources. More advantageous would be to ensure we consume these in moderation and focus on wholegrains, fruit and vegetables the majority of the time. This will ensure we are getting sufficient fibre In the diet and include starchy carbohydrates. These 2 groups contain a wider range of micronutrients, conveying a range of benefits to the body as well as energy.


Dietary fibre is a type of carbohydrate found almost exclusively in plants. Unlike other carbohydrates, it is not absorbed in the small intestine so reaches the colon.

Fibre helps the digestive system and keeps blood levels steady. Research has suggested diets high in fibre are associated with lower risk of cardiovascular disease, type 2 diabetes and bowel cancer (3). On average in the UK, we consume 19g of fibre per day.

This is way off the recommended intake of 30g per day.  

Research has increasingly shown how important the bacteria in our gut may be to our health, and It has been suggested that a fibre rich diet can help to increase the good bacteria in the gut.

Part of a balanced diet

As well as being a great source of energy and fibre, carbohydrates contain a range of micronutrients including antioxidants in the form of polyphenols and B vitamins, which help to release the energy from food. With carbohydrates found in so many different foods, restricting this food group can sometimes lead to nutrient deficiencies and is unlikely to be sustainable.

While cutting carbs in the short term is likely to lead to weight loss, it is unlikely this weight loss will be sustained when carbohydrates are reintroduced. The weight loss makes sense, 1g of carbohydrate holds 3g of water. So when we stop eating, or eat truly little carbohydrate, that water weight is gone.

Carbs also contain calories, so a if these calories are not replaced, hello weight loss!

In the long the term though, sticking to no or extremely low carbs is super hard and very restrictive. We know this equates to not being very sustainable in the long run (4) and this type of restriction may lead to an unhealthy or obsessive relationship with food.

Fad diets don’t work, a balanced and varied diet which includes food you love and that nourishes you is the goal we should all be aiming for.

Are there any risk of cutting carbohydrates from the diet?

As carbs are such a great energy source, removing this source can lead to feeling fatigued, tired and lethargic. Headaches, irritability, low mood and difficulty concentrating (remember glucose and the brain?) can also be a resulting factor. Not only this, but micronutrient deficiencies such as B vitamins and fibre can be of concern.

Low-carb diets often become high in saturated fat, which can lead to an increase in Low-Density Lipoprotein (LDL). This is commonly known as the bad cholesterol and can increase the risk of fatty liver and cardiovascular disease.

Lack of fibre in the diet from reducing carbohydrates can also increase the risk of constipation.

In some cases, following a low carbohydrate diet can be beneficial. The keto diet was specifically developed to help children with treatment-resistant epilepsy, as a short term measure to control seizures. Further evidence suggests low carbohydrate diets can be helpful in treating type 2 diabetes, when less than 14% of energy is coming from carbohydrates (6). However these diets are followed under strict supervision from a registered dietitian.

Let’s summarize

Carbohydrates are an important part of a balanced diet. They are the bodies main source of fuel, contain fibre, a range of micronutrients and are also beneficial for our brain and digestion. Focusing on starchy carbohydrates including wholegrains, fruit and vegetables is an important part of a balanced diet, both quality and quantity matter. Cutting a major food group out of the diet is a restrictive approach to eating, which is not sustainable in the long term, can lead to weight fluctuations and an unhealthy relationship with food.


  1. Wanjeck (2014)
  2. BNF
  3. NHS
  4. Bronus (2018)
  5. Snorgaard et al (2017)
  6. Oh et al (2020)
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