A common criticism of low-carbohydrate diets is that they fall short when it comes to micronutrients, such as low carb diets and fibre needs. As a dietitian, and a firm believer of the many potential benefits of a low-carb lifestyle, I have questioned this. How can a diet that promotes the intake of non-starch vegetables, a variety of proteins and lots of healthy fats be nutrient deplete?

Fortunately, I have a couple of very intelligent friends who shared this view and we set out to prove that a well-planned low-carb high fat diet can indeed be nutrient replete, and delicious! You can read the journal paper online here in the BMJ Open.

In this series of posts we will focus on the individual nutrients that seem to be of most concern for those questioning the adequacy of a lower carbohydrate approach.

First up is Fibre.

Fibre is the indigestible part of plant foods. It is a type of a carbohydrate that is known to improve the health of the digestive system. There are three types of fibre, each performing different functions in the gut.

Soluble fibre slows down stomach emptying and promotes the feeling of satiety and fullness. It can slow the digestion and absorption of more rapid acting carbohydrate, helping to manage post-meal blood glucose levels. It can also help to lower cholesterol levels.

Insoluble fibre absorbs water into the bowel and softens the stools. This promotes regular bowel movements that are easy to pass. It also promotes satiety and fullness.

Resistant starch is the undigested portion of fibre. It ends up in the large intestine where it can promote the production of healthy gut bacteria.

So fibre is definitely important!

When quizzed about where to find fibre in the diet, most people will answer with breads, cereals, or wholegrains. However, grains are not the only foods which offer fibre. There are a large number of low carbohydrate foods that contain a great amount of fibre per serve, such as non-starch vegetables, some fruits, nuts and seeds. Check out the table below for some fibre comparisons across lower carbohydrate and higher carbohydrate foods. 

High carbohydrate foodsLow carbohydrate foods
ItemFibre per 100gItemFibre per 100g
Apple2.4gAlmonds/almond meal8.8g
Banana2.7gAvocado2.8g
Bread (wholemeal)6.3gBroccoli3.6g
Carrot3.9gCauliflower2.7g
Lentils (cooked)3.7gChia seeds37.3g
Oats (raw)9.5gGreen beans3.1g
Pasta (wholemeal, cooked)5.5gSpinach 2.6g
Rice (brown, cooked)1.6gRaspberries 6.1g
Sweet potato (cooked)3.7gWalnuts6.4g

How much fibre do you need?

Fibre requirements are based on age and gender. The table below shows the grams of fibre per day required for males and females across the age ranges:

Age in years1-34-89-1314-1819+
Males – fibre requirements 14g18g24g28g30g
Females – fibre requirements 14g18g20g22g25g

What could this low carb, high fibre day look like?

MealFibre (grams)Carbohydrate (grams)
Breakfast – 2 x eggs, 1 cup spinach, small tomato, 4 small mushrooms, ½ avocado6.6g3.3g
Snack – 40g almonds3.5g1.9g
Lunch  – Chicken, feta and walnut (30g) salad – 50 g each of spinach, cucumber, capsicum, snow peas5.8g6.8g
Snack – 100g yoghurt and 100g frozen raspberries 4.5g15.9g
Dinner – Steak and vegetables with gravy – 100g each of broccoli, cauliflower, green beans9.4g10.1g
Total 29.7g fibre37.1g carbohydrate

As you can see, a low carbohydrate diet can very easily provide the recommended fibre requirements across the age ranges without the need for supplements or excessive amounts of a particular food group. If you are looking to lower your carbohydrate intake and concerned about your micronutrients, don’t go at it alone! Your dietitian can give you the tools you need to ensure your low carb approach hits all your nutrient targets.    

Amy Rush, Accredited Practicing Dietitian and Credentialled Diabetes Educator

For more information or to talk about a phone clinic appointment, email Amy at amy@type1familycentre.org.au

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