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 foods Low carbohydrate foods
Item Fibre per 100g Item Fibre per 100g
Apple 2.4g Almonds/almond meal 8.8g
Banana 2.7g Avocado 2.8g
Bread (wholemeal) 6.3g Broccoli 3.6g
Carrot 3.9g Cauliflower 2.7g
Lentils (cooked) 3.7g Chia seeds 37.3g
Oats (raw) 9.5g Green beans 3.1g
Pasta (wholemeal, cooked) 5.5g Spinach 2.6g
Rice (brown, cooked) 1.6g Raspberries 6.1g
Sweet potato (cooked) 3.7g Walnuts 6.4g

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 years 1-3 4-8 9-13 14-18 19+
Males – fibre requirements 14g 18g 24g 28g 30g
Females – fibre requirements 14g 18g 20g 22g 25g

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

Meal Fibre (grams) Carbohydrate (grams)
Breakfast – 2 x eggs, 1 cup spinach, small tomato, 4 small mushrooms, ½ avocado 6.6g 3.3g
Snack – 40g almonds 3.5g 1.9g
Lunch  – Chicken, feta and walnut (30g) salad – 50 g each of spinach, cucumber, capsicum, snow peas 5.8g 6.8g
Snack – 100g yoghurt and 100g frozen raspberries 4.5g 15.9g
Dinner – Steak and vegetables with gravy – 100g each of broccoli, cauliflower, green beans 9.4g 10.1g
Total 29.7g fibre 37.1g 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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