fibre… net carbs or total carbs?

Looking at the foods sitting above the trend line the chart below it appears that the foods with the greatest insulin response compared to what would be predicted by carbohydrate and protein tend to be the ones that are more processed such as ice-cream, baked beans, pancakes and Jelly Beans.

On the lower side of the trend line we have less processed foods (e.g. full cream milk, navy beans, porridge and All Bran with added fibre).

Microsoft Word Document 25032015 40944 AM.bmp

Processed foods tend to contain less fibre, while carbohydrates in their original state typically contain more fibre.  Fibre is indigestible carbohydrate and hence does not raise blood sugars or require insulin.

Fibre is also important for the health of our gut and feeds the good bacteria in our digestive tract.

Could it be possible to also use fibre as a proxy for the level of processing to help refine the prediction of insulin demand by different foods?

In order to test whether fibre is useful to predict insulin demand I tested the relationship between carbohydrates plus different amounts of the fibre in the various foods.

The best correlation was achieved by removing all of the fibre.  Using net carbs gives an increased correlation compared to the carbohydrates alone (i.e. R2 = 0.435 compared to R2 = 0.482).

Microsoft Word Document 25032015 41148 AM.bmp

Considering the carbohydrates, protein and fibre in a food enables us to more accurately predict insulin demand.

This concept is known in the low carb community as “net carbs”.  If you’re trying count carbohydrates to manage insulin people are often advised to consider the total carbohydrates minus the fibre as fibre cannot be digested but is rather digested by our intestinal bacteria.

This aligns with the understanding that carbohydrates consumed with the packaging that they came with (i.e. fibre) do not have as big an effect on insulin.

This relationship might be part of the reason why many populations have maintained good health on a higher level of carbohydrate consumed in their raw natural state compared to when they come from the supermarket in boxes with barcodes.

There is some disagreement on how to deal with fibre on a restricted carbohydrate diet:

  • Some people say you should ignore fibre because “net carbs” is just a marketing ploy.
  • Some people choose to count half the fibre as carbs as a middle ground.
  • Experienced type 1 diabetics who monitor their blood sugars using continuous glucose meters will tell you that the fibre in their veggies will not raise their blood sugars however they ignore the fibre in packaged foods because it does raise their blood sugar.

My interpretation of the food insulin index data indicates that real fibre in foods is indigestible and hence does not raise blood sugar and require insulin.  However excess cooking and processing will soften this fibre and make it digestible.

It appears that the fibre in a food is a useful proxy for the level of processing and helps us to better predict the insulin demand of a food.

If you want to reduce your insulin load you can increase the amount of non-starchy veggies such as spinach, broccoli, mushrooms, Brussel sprouts and kale in your diet.

If you’re using packaged diet products then I suggest you ignore the fibre content, or maybe don’t buy them in the first place.

The major problem I see with encouraging people to consider total carbohydrates rather than net carbohydrates is that it will encourage people to avoid vegetables which not be optimal for health in the long term.  The reality is, when you take fibre into account, you can eat a lot of non-starchy vegetables without significantly impacting your net carbohydrates.

[next article…  how do you like your veggies… cooked or raw?]

[this post is part of the insulin index series]

[Like what you’re reading?  Skip to the full story here.]

how do you like your veggies… cooked or raw?

35 thoughts on “fibre… net carbs or total carbs?”

  1. You always have such great , scientifically based information presented in an easily understandable way. I know that cooking vegetables reduces their fiber content do you know by how much? Obviously the less well cooked the better in terms of fiber. I am wondering specifically about artichokes that have been boiled so that they are soft enough to eat. They contain 14 grams of carbs and around 10 of those are fiber. Would it be reasonable to assume that I could deduct half? Leaving 9 net carbs total.

    Liked by 1 person

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